Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html
"Using the middle connector and leaving the end connector unattached
...... leaves part of the cable "dangling". This is called a stub and creates
much worse electrical characteristics on the cable, due to reflections
from the unterminated ends of the cable wires. It is not recommended."

I 1st ignored this warning, & found my Toshiba cd drive ( using cable
select, & assigned by Award bios as 2nd channel's slave device )
though can play any VCD just as well, cannot pass BCM diagnostic (
blue screen of "fatal error" appears in Win98se ) unless I use the end
connector of this 80 wire cable to connect this drive ( i.e. bios
assigned as master device ) to my ( VIA ) kt266a 's hdd controller.

Does any1 here have a similar experience ? If this warning is valid,
then why does no mboard / hdd / cdd / dvd / cable manufacturer warn
users of this requirement ?

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage TE Cheah wrote:
Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html
"Using the middle connector and leaving the end connector unattached
..... leaves part of the cable "dangling". This is called a stub and creates
much worse electrical characteristics on the cable, due to reflections
from the unterminated ends of the cable wires. It is not recommended."

I 1st ignored this warning, & found my Toshiba cd drive ( using cable
select, & assigned by Award bios as 2nd channel's slave device )
though can play any VCD just as well, cannot pass BCM diagnostic (
blue screen of "fatal error" appears in Win98se ) unless I use the end
connector of this 80 wire cable to connect this drive ( i.e. bios
assigned as master device ) to my ( VIA ) kt266a 's hdd controller.

Does any1 here have a similar experience ? If this warning is valid,
then why does no mboard / hdd / cdd / dvd / cable manufacturer warn
users of this requirement ?

First, IDE cables are not terminated. That means that for the drive on
the middle connector it makes no difference whether there is a drive
at the end or not! If anybody says different, then they do not
understand the subject matter. In SCSI cables (what likley causes
the confusion) it is a different matter: The last device on an
SCSI bus _is_ terminated and havinf no device there either means the
bus is not terminated or it is teminated somewhere in the middle.
Both useually cause mor or less secvere problems. Again, the same is
_not_ true for IDE cables. The device at the end does _nothing_ for
signal quality when the controller and the device in the middle
talk to each other. From the point of view of the device in the
middle, the end-connector is allways empty. The only exception is
during the power-on sequence, but not during normal operation.

That said, yes, the electical characteristics are worse, but any
well-designed IDE device needs to be able to deal with it. I do have a
TEAC CD-writer (CD-W540E) that is sensitive to rounded cables when
data is transferred to the device. I get bit-errors on the written
CDs. The burner has no problems with normal flat cables, no matter
what connector it is on. I would say the device is borderline broken
by design. If you use standard length flat cables then the CD drive
or IDE controller has likely been damaged, e.g. by static electricity.
It usually makes digital I/Os much more sensitive to noise.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

You are correct as far as what that particular web page refers to: 40-pin,
80-wire IDE cables.

It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

http://www.pcguide.com/ref/hdd/if/ide/conf_Cable80.htm
--
Glen Ventura, MS MVP Shell/User, A+

"Arno Wagner" wrote in message
...
In comp.sys.ibm.pc.hardware.storage TE Cheah wrote:
Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html
"Using the middle connector and leaving the end connector unattached
..... leaves part of the cable "dangling". This is called a stub and
creates
much worse electrical characteristics on the cable, due to reflections
from the unterminated ends of the cable wires. It is not recommended."

I 1st ignored this warning, & found my Toshiba cd drive ( using cable
select, & assigned by Award bios as 2nd channel's slave device )
though can play any VCD just as well, cannot pass BCM diagnostic (
blue screen of "fatal error" appears in Win98se ) unless I use the end
connector of this 80 wire cable to connect this drive ( i.e. bios
assigned as master device ) to my ( VIA ) kt266a 's hdd controller.

Does any1 here have a similar experience ? If this warning is valid,
then why does no mboard / hdd / cdd / dvd / cable manufacturer warn
users of this requirement ?

First, IDE cables are not terminated. That means that for the drive on
the middle connector it makes no difference whether there is a drive
at the end or not! If anybody says different, then they do not
understand the subject matter. In SCSI cables (what likley causes
the confusion) it is a different matter: The last device on an
SCSI bus _is_ terminated and havinf no device there either means the
bus is not terminated or it is teminated somewhere in the middle.
Both useually cause mor or less secvere problems. Again, the same is
_not_ true for IDE cables. The device at the end does _nothing_ for
signal quality when the controller and the device in the middle
talk to each other. From the point of view of the device in the
middle, the end-connector is allways empty. The only exception is
during the power-on sequence, but not during normal operation.

That said, yes, the electical characteristics are worse, but any
well-designed IDE device needs to be able to deal with it. I do have a
TEAC CD-writer (CD-W540E) that is sensitive to rounded cables when
data is transferred to the device. I get bit-errors on the written
CDs. The burner has no problems with normal flat cables, no matter
what connector it is on. I would say the device is borderline broken
by design. If you use standard length flat cables then the CD drive
or IDE controller has likely been damaged, e.g. by static electricity.
It usually makes digital I/Os much more sensitive to noise.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Arno Wagner" wrote in message
In comp.sys.ibm.pc.hardware.storage TE Cheah wrote:
Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html
"Using the middle connector and leaving the end connector unattached
..... leaves part of the cable "dangling". This is called a stub and creates
much worse electrical characteristics on the cable, due to reflections
from the unterminated ends of the cable wires. It is not recommended."

I 1st ignored this warning, & found my Toshiba cd drive ( using cable
select, & assigned by Award bios as 2nd channel's slave device )
though can play any VCD just as well, cannot pass BCM diagnostic (
blue screen of "fatal error" appears in Win98se ) unless I use the end
connector of this 80 wire cable to connect this drive ( i.e. bios
assigned as master device ) to my ( VIA ) kt266a 's hdd controller.

Does any1 here have a similar experience ? If this warning is valid,
then why does no mboard / hdd / cdd / dvd / cable manufacturer warn
users of this requirement ?

First, IDE cables are not terminated.

Neither are SCSI.

That means that for the drive on the middle connector it makes no difference
whether there is a drive at the end or not!

Yes it does. Even more so, in fact.

If anybody says different, then they do not understand the subject matter.

Practicing before that mirror again, babblemouth?

It's you who obviously doesn't understand.

In SCSI cables (what likley causes the confusion) it is a different matter:

No. it's not. Just a different solution to a problem.
Terminators come seperate from drives.

The last device on an SCSI bus _is_ terminated and havinf no device there
either means the bus is not terminated or it is teminated somewhere in the middle.

Utter nonsense, clueless as always.
Drive internal terminators were last seen on
Ultra SCSI devices and only on few of those.

Both useually cause mor or less secvere problems.

Have you been boozing again, babblemouth?

Again, the same is _not_ true for IDE cables.

Corse it is.

The device at the end does _nothing_ for signal quality when
the controller and the device in the middle talk to each other.

Corse it does. And it's not different to SCSI either.

From the point of view of the device in the
middle, the end-connector is allways empty.

Gee, where is the difference with SCSI there.

The only exception is during the power-on sequence,

Nonsense.

but not during normal operation.

That said, yes, the electical characteristics are worse, but any
well-designed IDE device needs to be able to deal with it.

And with Ultra DMA they do by introducing series termination.
It's on the drives that can do Ultra-DMA.

[Stupid off-topic rant snipped]


Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"glee" wrote in message
...
You are correct as far as what that particular web page refers to: 40-pin,
80-wire IDE cables.

Correction/Typo: That should read: 40-pin, 40-wire IDE cables. Brain
failure (again)!

I'm not sure I should go so far as to say you are correct there, either.....
there can and will be the possibility of "electrical disturbances"
regardless.

....glen

It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

http://www.pcguide.com/ref/hdd/if/ide/conf_Cable80.htm
--
Glen Ventura, MS MVP Shell/User, A+

"Arno Wagner" wrote in message
...
In comp.sys.ibm.pc.hardware.storage TE Cheah wrote:
Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html
"Using the middle connector and leaving the end connector unattached
..... leaves part of the cable "dangling". This is called a stub and
creates
much worse electrical characteristics on the cable, due to reflections
from the unterminated ends of the cable wires. It is not recommended."

I 1st ignored this warning, & found my Toshiba cd drive ( using cable
select, & assigned by Award bios as 2nd channel's slave device )
though can play any VCD just as well, cannot pass BCM diagnostic (
blue screen of "fatal error" appears in Win98se ) unless I use the end
connector of this 80 wire cable to connect this drive ( i.e. bios
assigned as master device ) to my ( VIA ) kt266a 's hdd controller.

Does any1 here have a similar experience ? If this warning is valid,
then why does no mboard / hdd / cdd / dvd / cable manufacturer warn
users of this requirement ?

First, IDE cables are not terminated. That means that for the drive on
the middle connector it makes no difference whether there is a drive
at the end or not! If anybody says different, then they do not
understand the subject matter. In SCSI cables (what likley causes
the confusion) it is a different matter: The last device on an
SCSI bus _is_ terminated and havinf no device there either means the
bus is not terminated or it is teminated somewhere in the middle.
Both useually cause mor or less secvere problems. Again, the same is
_not_ true for IDE cables. The device at the end does _nothing_ for
signal quality when the controller and the device in the middle
talk to each other. From the point of view of the device in the
middle, the end-connector is allways empty. The only exception is
during the power-on sequence, but not during normal operation.

That said, yes, the electical characteristics are worse, but any
well-designed IDE device needs to be able to deal with it. I do have a
TEAC CD-writer (CD-W540E) that is sensitive to rounded cables when
data is transferred to the device. I get bit-errors on the written
CDs. The burner has no problems with normal flat cables, no matter
what connector it is on. I would say the device is borderline broken
by design. If you use standard length flat cables then the CD drive
or IDE controller has likely been damaged, e.g. by static electricity.
It usually makes digital I/Os much more sensitive to noise.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"TE Cheah" wrote:
"Using the middle connector and leaving the end connector unattached
..... leaves part of the cable "dangling". This is called a stub and creates
much worse electrical characteristics on the cable, due to reflections
from the unterminated ends of the cable wires. It is not recommended."


This is true - that it's not recommended - and for the reason given.
An open circuit at the end and a short circuit at the end of a cable
are equally reflective of signals. And that is why the cable length and
the connector spacing is specified for IDE cables - to minimize the
effects of signal reflections that do occur. BUT... some circuit designs
are more tolerant of signal reflections than others, and *sometimes*
you can get away with the end connector empty. In my PC with a SIIG
PCI IDE controller and Maxtor DiamondMax Plus 9 hard drives, an
empty end connector seems not to matter - bootups and disk cloning
seem to take the same amount of time when the destination disk is on
the middle connectore or on the end connector of channel 1. But I
wouldn't count on that being the case for all hard drives and for all
IDE controllers, and I don't even do that in my PC in normal procedure.

If your question derives from a desire to keep down the amount
of ribbon cable in the PC's interior, try "round" cables. They come in
various lengths in both single connector and dual connector forms,
and some models have aluminum or copper braid shielding.
They do "flout the ATA specs" as one poster would complain, but
I've had no problems with them, and they do clean up some
"impossibly crowded" case interiors. Check 'em out:
http://svc.com/cables-ata-100-133-round-cables.html

*TimDaniels*

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage glee wrote:
You are correct as far as what that particular web page refers to: 40-pin,
80-wire IDE cables.

Same for 40 pin 40 wire cables.

It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.

With cable select the device at the end is the master (during
boot-up) and the device in the middle the slave. Some devices will
fail to start or have problems if they are used as slave and no master
is present. AFAIK this is more of a historic problem today.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage glee wrote:
"glee" wrote in message
...
You are correct as far as what that particular web page refers to: 40-pin,
80-wire IDE cables.

Correction/Typo: That should read: 40-pin, 40-wire IDE cables. Brain
failure (again)!

I'm not sure I should go so far as to say you are correct there, either.....
there can and will be the possibility of "electrical disturbances"
regardless.

True. There will be signal echoes on the wires. The enpoint
will indeed get a significantly cleaner signal.

But as I said a device at the end will not improve the
situation for the device in the middle in any way. It does not
matter whether it is an 40/40 or an 40/80 cable. IDE devices
just don't do any termination. That means that while inactive
the IDE device at the end will just be a very high resistance
digital input. No effect on electical echoes on the wires at
all.

If you have a borderline broken device, then you may observe it
only working on the cable end. However if you have a correctly
working device it must work in both positions, regardless of
whether another device is present. (Disregarding the CS/jumpers
issue for the moment.)

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Arno Wagner wrote:
In comp.sys.ibm.pc.hardware.storage glee
wrote:
"glee" wrote in message
...
You are correct as far as what that particular web page refers to:
40-pin, 80-wire IDE cables.

Correction/Typo: That should read: 40-pin, 40-wire IDE cables. Brain
failure (again)!

I'm not sure I should go so far as to say you are correct there,
either..... there can and will be the possibility of "electrical
disturbances" regardless.

True. There will be signal echoes on the wires. The enpoint
will indeed get a significantly cleaner signal.

But as I said a device at the end will not improve
the situation for the device in the middle in any way.

Wrong, it reduces the 'signal echoes' which are actually
the sharp edges getting reflected off the impedance
discontinuity. Thats reduced with a drive on the end.

It does not matter whether it is an 40/40 or an 40/80 cable.
IDE devices just don't do any termination.

Irrelevant. The drive has a different impedance to no drive.

That means that while inactive the IDE device at the
end will just be a very high resistance digital input.

Wrong again.

No effect on electical echoes on the wires at all.

Wrong again. Its significantly different impedance to no drive.

If you have a borderline broken device, then you may observe it
only working on the cable end. However if you have a correctly
working device it must work in both positions, regardless of
whether another device is present. (Disregarding the CS/jumpers
issue for the moment.)

Separate issue entirely.

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Arno Wagner wrote:
In comp.sys.ibm.pc.hardware.storage glee
wrote:
You are correct as far as what that particular web page refers to:
40-pin, 80-wire IDE cables.

Same for 40 pin 40 wire cables.

It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require
particular devices to be attached to particular connectors on those
cables, and that the end connector *not* be left vacant. This is
especially true in the example given in the original post: using
Cable Select.

In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.

Pity about what the ata standard recommends.

With cable select the device at the end is the master (during
boot-up) and the device in the middle the slave. Some devices will
fail to start or have problems if they are used as slave and no master
is present. AFAIK this is more of a historic problem today.

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Arno Wagner" wrote:
IDE devices
just don't do any termination. That means that while inactive
the IDE device at the end will just be a very high resistance
digital input. No effect on electical echoes on the wires at
all.


If the input impedance of the device matches that of the
cable, there will be no reflection. That is why high-freq comm
receiver designers try to match the input impedance to the
cable impedance. Are you saying that the input impedance
of ATA devices do not match the impedance of IDE ribbon
cable?

*TimDaniels*

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Arno Wagner" wrote:
glee wrote:
It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


You are correct that *on a single IDE channel*, the device arrangement
can be Master/Slave or Slave/Master or single Master or single Slave.
What is not allowed by the IDE controller, though, is Master/Master and
Slave/Slave on the same channel. But on different channels, you could
have ch.0 Master/ ch. 1 Master and ch. 0 Slave/ ch. 1 Slave and
ch. 0 Slave/Master/ch. 1 Master/Slave. The arrangement prohibited is
having the same jumpering for both devices on the same IDE channel,
i.e. on the same cable. That is imposed by the controller's need to be
able to tell the two devices apart which are on the same cable. I think
that's what you intended to express, but it wasn't clear.

And the implications go farther: A Slave HD can be the "boot drive"
just as well as well as a Master HD. All that is required is that the HD
be at the head of the HD boot order. The default settings (or settings in
BIOSes which don't enable adjustment of the HD boot order) put the
Master on ch. 0 at the head of the HD boot order. But this can be
changed by readjustment of the HD boot order. Indeed, it's quite
legitimate to have the Slave on ch. 1 (the secondary IDE channel) be
the "boot drive".

*TimDaniels*

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Timothy Daniels wrote
Arno Wagner wrote

IDE devices just don't do any termination. That means that while
inactive the IDE device at the end will just be a very high resistance
digital input. No effect on electical echoes on the wires at all.

If the input impedance of the device matches that of the
cable, there will be no reflection. That is why high-freq comm
receiver designers try to match the input impedance to the
cable impedance. Are you saying that the input impedance
of ATA devices do not match the impedance of IDE ribbon cable?

Yep, if that was the system, it would be specified in the standard.

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Arno Wagner wrote:


In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


On more that one occasion, because of the layout of the motherboard
and the design of the computer case, I have connected drives using the
middle connector for the motherboard with a drive at each end. 40
wire cables with master/slave jumpers set appropriately, of course.
But zero problems with using the drives.

Ron Martell Duncan B.C. Canada
--
Microsoft MVP (1997 - 2006)
On-Line Help Computer Service
http://onlinehelp.bc.ca

"Anyone who thinks that they are too small to make a difference
has never been in bed with a mosquito."

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Arno Wagner" wrote in message
In comp.sys.ibm.pc.hardware.storage glee wrote:
You are correct as far as what that particular web page refers to: 40-pin,
80-wire IDE cables.

Same for 40 pin 40 wire cables.

It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.

With cable select the device at the end is the master (during
boot-up) and the device in the middle the slave. Some devices will
fail to start or have problems if they are used as slave and no master
is present.

AFAIK

Which is zip.

this is more of a historic problem today.

Nope, most if not all harddrives still have jumpers for that situation.


Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Stop feeding the swiss troll.

"Timothy Daniels" wrote in message
"Arno Wagner" wrote:
glee wrote:
It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


You are correct that *on a single IDE channel*, the device arrangement
can be Master/Slave or Slave/Master or single Master or single Slave.
What is not allowed by the IDE controller, though, is Master/Master and
Slave/Slave on the same channel. But on different channels, you could
have ch.0 Master/ ch. 1 Master and ch. 0 Slave/ ch. 1 Slave and
ch. 0 Slave/Master/ch. 1 Master/Slave. The arrangement prohibited is
having the same jumpering for both devices on the same IDE channel,
i.e. on the same cable. That is imposed by the controller's need to be
able to tell the two devices apart which are on the same cable. I think
that's what you intended to express, but it wasn't clear.

And the implications go farther: A Slave HD can be the "boot drive"
just as well as well as a Master HD. All that is required is that the HD
be at the head of the HD boot order. The default settings (or settings in
BIOSes which don't enable adjustment of the HD boot order) put the
Master on ch. 0 at the head of the HD boot order. But this can be
changed by readjustment of the HD boot order. Indeed, it's quite
legitimate to have the Slave on ch. 1 (the secondary IDE channel) be
the "boot drive".

*TimDaniels*

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Multigroup post thwarted. I don't particularly like some of the
participants at one particular newsgroup.

ATA basics. Slave in the middle, master on the end. Using cable select or
master/slave jumpers, makes no difference. There must be a master for a
slave to exist. This is part of the timing aspect for ATA.

There's alot of things motherboard makers don't provide information about.
Most of use muddle our ways through to learn the hard way. Or, stumble upon
a good website to fill that void.

Pcguide is a good website. ATA has no terminations per se like scsi. It is
however a stub, and reflections are a result. Poor explanation provided,
but symptoms are nonetheless accurate.
--
Jonny
"TE Cheah" wrote in message ...
Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html
"Using the middle connector and leaving the end connector unattached
..... leaves part of the cable "dangling". This is called a stub and
creates
much worse electrical characteristics on the cable, due to reflections
from the unterminated ends of the cable wires. It is not recommended."

I 1st ignored this warning, & found my Toshiba cd drive ( using cable
select, & assigned by Award bios as 2nd channel's slave device )
though can play any VCD just as well, cannot pass BCM diagnostic (
blue screen of "fatal error" appears in Win98se ) unless I use the end
connector of this 80 wire cable to connect this drive ( i.e. bios
assigned as master device ) to my ( VIA ) kt266a 's hdd controller.

Does any1 here have a similar experience ? If this warning is valid,
then why does no mboard / hdd / cdd / dvd / cable manufacturer warn
users of this requirement ?

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage Oscar wrote:
Arno Wagner wrote:
In comp.sys.ibm.pc.hardware.storage glee
wrote:
"glee" wrote in message
...
You are correct as far as what that particular web page refers to:
40-pin, 80-wire IDE cables.

Correction/Typo: That should read: 40-pin, 40-wire IDE cables. Brain
failure (again)!

I'm not sure I should go so far as to say you are correct there,
either..... there can and will be the possibility of "electrical
disturbances" regardless.

True. There will be signal echoes on the wires. The enpoint
will indeed get a significantly cleaner signal.

But as I said a device at the end will not improve
the situation for the device in the middle in any way.

Wrong, it reduces the 'signal echoes' which are actually
the sharp edges getting reflected off the impedance
discontinuity. Thats reduced with a drive on the end.

It does not matter whether it is an 40/40 or an 40/80 cable.
IDE devices just don't do any termination.

Irrelevant. The drive has a different impedance to no drive.

Very relevant. An unterminated drive connected to the
end actually makes things worse for the device in the
middle.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage Timothy Daniels wrote:
"Arno Wagner" wrote:
IDE devices
just don't do any termination. That means that while inactive
the IDE device at the end will just be a very high resistance
digital input. No effect on electical echoes on the wires at
all.


If the input impedance of the device matches that of the
cable, there will be no reflection. That is why high-freq comm
receiver designers try to match the input impedance to the
cable impedance. Are you saying that the input impedance
of ATA devices do not match the impedance of IDE ribbon
cable?

You are entirely correct on how signal termination works.

The input inpedance of an ATA device is a CMOS input plus ESD
protection. Some mega Ohm or more. The ATA ribbon cable has
an impedance of 200 Ohm, if I remember correctly. No termination
effect at all.

For the device in the middle that is how it should be.
Termination in the middle of a signal path is very bad. But
the end-device has no terminator it turns on. I suspect that
at some time that was planned, but at least the last time
I looked at the physical ATA bus characteristics, there was
no mention of it anywhere.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage Timothy Daniels wrote:
"Arno Wagner" wrote:
glee wrote:
It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


You are correct that *on a single IDE channel*, the device arrangement
can be Master/Slave or Slave/Master or single Master or single Slave.
What is not allowed by the IDE controller, though, is Master/Master and
Slave/Slave on the same channel. But on different channels, you could
have ch.0 Master/ ch. 1 Master and ch. 0 Slave/ ch. 1 Slave and
ch. 0 Slave/Master/ch. 1 Master/Slave. The arrangement prohibited is
having the same jumpering for both devices on the same IDE channel,
i.e. on the same cable. That is imposed by the controller's need to be
able to tell the two devices apart which are on the same cable. I think
that's what you intended to express, but it wasn't clear.

Sorry. Yes, that was what I wanted to say. Of course there is not
physical interaction between multiple IDE busses / channels (of which
you incidentially can have more than two or only one).

And the implications go farther: A Slave HD can be the "boot drive"
just as well as well as a Master HD. All that is required is that the HD
be at the head of the HD boot order. The default settings (or settings in
BIOSes which don't enable adjustment of the HD boot order) put the
Master on ch. 0 at the head of the HD boot order. But this can be
changed by readjustment of the HD boot order. Indeed, it's quite
legitimate to have the Slave on ch. 1 (the secondary IDE channel) be
the "boot drive".

Again true. It is a start-up issue for the device detection only. Not
for booting. The Master is supposed to be detected first. Then the
slave. After that both are identical, except that they have different
select signals. And yes, the BIOS is free to assign them any order
wanted.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage Ron Martell wrote:
Arno Wagner wrote:


In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


On more that one occasion, because of the layout of the motherboard
and the design of the computer case, I have connected drives using the
middle connector for the motherboard with a drive at each end. 40
wire cables with master/slave jumpers set appropriately, of course.
But zero problems with using the drives.

Interesting.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Yes, I remember those days before speed of data movement became more
critical for ATA timing aspect to become an issue. Had same experiences,
Ron.
Fraid we have to be more compliant nowadays.
--
Jonny
"Ron Martell" wrote in message
...
Arno Wagner wrote:


In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


On more that one occasion, because of the layout of the motherboard
and the design of the computer case, I have connected drives using the
middle connector for the motherboard with a drive at each end. 40
wire cables with master/slave jumpers set appropriately, of course.
But zero problems with using the drives.

Ron Martell Duncan B.C. Canada
--
Microsoft MVP (1997 - 2006)
On-Line Help Computer Service
http://onlinehelp.bc.ca

"Anyone who thinks that they are too small to make a difference
has never been in bed with a mosquito."

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Arno Wagner wrote
wrote
Arno Wagner wrote
glee wrote
glee wrote

You are correct as far as what that particular
web page refers to:40-pin, 80-wire IDE cables.

Correction/Typo: That should read: 40-pin, 40-wire IDE cables.
Brain failure (again)!

I'm not sure I should go so far as to say you are correct there,
either..... there can and will be the possibility of "electrical
disturbances" regardless.

True. There will be signal echoes on the wires. The enpoint
will indeed get a significantly cleaner signal.

But as I said a device at the end will not improve
the situation for the device in the middle in any way.

Wrong, it reduces the 'signal echoes' which are actually
the sharp edges getting reflected off the impedance
discontinuity. Thats reduced with a drive on the end.

It does not matter whether it is an 40/40 or an 40/80 cable.
IDE devices just don't do any termination.

Irrelevant. The drive has a different impedance to no drive.

Very relevant.

Nope.

An unterminated drive connected to the end actually
makes things worse for the device in the middle.

Nope. The impedance of that drive is
better reflections wise than no drive at all.

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Arno Wagner wrote
Timothy Daniels wrote
Arno Wagner wrote

IDE devices just don't do any termination.
That means that while inactive the IDE device
at the end will just be a very high resistance
digital input. No effect on electical echoes
on the wires at all.

If the input impedance of the device matches that of the
cable, there will be no reflection. That is why high-freq comm
receiver designers try to match the input impedance to the
cable impedance. Are you saying that the input impedance
of ATA devices do not match the impedance of IDE ribbon
cable?

You are entirely correct on how signal termination works.

The input inpedance of an ATA device is a CMOS
input plus ESD protection. Some mega Ohm or more.

Its more complicated than that with most
of the lines that arent pure receivers.

The ATA ribbon cable has an impedance of 200 Ohm,
if I remember correctly. No termination effect at all.

Wrong, the drive presents an impedance
that is different to no drive at all.

For the device in the middle that is how it should be.
Termination in the middle of a signal path is very bad.

Its more complicated than that too if termination is used.

But the end-device has no terminator it turns on.

It has an impedance anyway.

I suspect that at some time that was planned,

Not a shred of evidence of that. ATA has
always been an unterminated system.

but at least the last time I looked at the physical ATA bus
characteristics, there was no mention of it anywhere.

Because it has always been an unterminated system.

That does NOT mean that the drive impedance isnt relevant tho.

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Arno Wagner" wrote in message
In comp.sys.ibm.pc.hardware.storage Timothy Daniels wrote:
"Arno Wagner" wrote:
glee wrote:
It is my understanding however (and the recommendation of the
manufacturers), that 40-pin, 80-wire IDE cables *do* require particular
devices to be attached to particular connectors on those cables, and that
the end connector *not* be left vacant. This is especially true in the
example given in the original post: using Cable Select.

In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


You are correct that *on a single IDE channel*, the device arrangement
can be Master/Slave or Slave/Master or single Master or single Slave.
What is not allowed by the IDE controller, though, is Master/Master and
Slave/Slave on the same channel. But on different channels, you could
have ch.0 Master/ ch. 1 Master and ch. 0 Slave/ ch. 1 Slave and
ch. 0 Slave/Master/ch. 1 Master/Slave. The arrangement prohibited is
having the same jumpering for both devices on the same IDE channel,
i.e. on the same cable. That is imposed by the controller's need to be
able to tell the two devices apart which are on the same cable. I think
that's what you intended to express, but it wasn't clear.

Sorry.

Yes, that was what I wanted to say.

And that's what you said. Too stupid even to understand it's own ramblings.

Of course there is not physical interaction between multiple IDE busses /
channels (of which you incidentially can have more than two or only one).

Babble, babble, rant.


And the implications go farther: A Slave HD can be the "boot drive"
just as well as well as a Master HD. All that is required is that the HD
be at the head of the HD boot order. The default settings (or settings in
BIOSes which don't enable adjustment of the HD boot order) put the
Master on ch. 0 at the head of the HD boot order. But this can be
changed by readjustment of the HD boot order. Indeed, it's quite
legitimate to have the Slave on ch. 1 (the secondary IDE channel) be
the "boot drive".

Again true.

It is a start-up issue for the device detection only.

Nope. Device initialization at power-up or reset only.

Not for booting.

The Master is supposed to be detected first. Then the slave.

Completely irrelevant.

After that both are identical, except that they have different
select signals.

No they don't.

And yes, the BIOS is free to assign them any order wanted.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Arno Wagner" wrote in message
In comp.sys.ibm.pc.hardware.storage Ron Martell wrote:
Arno Wagner wrote:


In fact cable select is the only reason for this. There is no other
one. If you jumper the devices to slave/master you can have them in
arbitrary order, number and position on these cables.


On more than one occasion, because of the layout of the motherboard
and the design of the computer case, I have connected drives using the
middle connector for the motherboard with a drive at each end. 40
wire cables with master/slave jumpers set appropriately, of course.
But zero problems with using the drives.

Interesting.

In that it shows how you don't have the faintest clue.


Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Your comments are confused. There's no such thing, in SCSI or IDE, as a
terminated or unterminated device. There's a device, a terminator, or no
device. The terminator is a cheap way of pretending some sort of device is
connected, and it's important for SCSI mainly because of the cable lengths
involved. It doesn't really matter for IDE because the impact of an
unterminated connector on the signal quality (ringing, overshoot) is much
less with the shorter lengths involved, and the IDE interface can cope with
it. But there is still a difference in signal quality between an IDE cable
with a device connected and one without.

An 'Inactive' IDE device is not particularly high resistance, and certainly
has an impact on signal quality compared with an open connector.
--
Jeff Richards
MS MVP (Windows - Shell/User)
"Arno Wagner" wrote in message
...
In comp.sys.ibm.pc.hardware.storage glee wrote:

But as I said a device at the end will not improve the
situation for the device in the middle in any way. It does not
matter whether it is an 40/40 or an 40/80 cable. IDE devices
just don't do any termination. That means that while inactive
the IDE device at the end will just be a very high resistance
digital input. No effect on electical echoes on the wires at
all.

If you have a borderline broken device, then you may observe it
only working on the cable end. However if you have a correctly
working device it must work in both positions, regardless of
whether another device is present. (Disregarding the CS/jumpers
issue for the moment.)

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage Jeff Richards wrote:
Your comments are confused. There's no such thing, in SCSI or IDE, as a
terminated or unterminated device. There's a device, a terminator, or no
device. The terminator is a cheap way of pretending some sort of device is
connected, and it's important for SCSI mainly because of the cable lengths
involved. It doesn't really matter for IDE because the impact of an
unterminated connector on the signal quality (ringing, overshoot) is much
less with the shorter lengths involved, and the IDE interface can cope with
it. But there is still a difference in signal quality between an IDE cable
with a device connected and one without.

An 'Inactive' IDE device is not particularly high resistance, and certainly
has an impact on signal quality compared with an open connector.

SCSI is complicated today. U2W cables are actively terminated. Older
standards allow terminated devices (i.e. devices with internal
termion) as well as external terminators.

As it turns out UDMA capable devices has some sort of half-assed
device terminaton, i.e. _every_ device on the bus has some pull-up
or pull-down resistirs. Quite inelegant IMO.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

Folkert Rienstra wrote:

AFAIK

Which is zip.

LOL

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Jeff Richards" wrote in message
Your comments are confused.

And your's are any better?

There's no such thing, in SCSI or IDE, as a terminated or unterminated device.

Well, there is in the physical sense, as a device that provides the termination.

There's a device, a terminator, or no device.

The terminator is a cheap way of pretending some sort of device is connected,

Uh no. It is pretending that the cable is endless.

and it's important for SCSI mainly because of the cable lengths involved.

In part.
Without any termination a SCSI bus doesn't function at all, nomatter how short.

It doesn't really matter for IDE because the impact of an unterminated
connector on the signal quality (ringing, overshoot) is much less with the
shorter lengths involved,

In part.

and the IDE interface can cope with it.

No, it *can't*. It *could* when interface speeds were still (s)low and
the *interface* wasn't yet acting like a *bus*, ie a *transmission line*.
Changes were necessary to keep it working with the higher UDMA modes.
One of those came to be known as series termination.

But there is still a difference in signal quality between an IDE cable
with a device connected and one without.

An 'Inactive' IDE device is not particularly high resistance, and certainly
has an impact on signal quality compared with an open connector.

In comp.sys.ibm.pc.hardware.storage glee wrote:

But as I said a device at the end will not improve the
situation for the device in the middle in any way. It does not
matter whether it is an 40/40 or an 40/80 cable. IDE devices
just don't do any termination. That means that while inactive
the IDE device at the end will just be a very high resistance
digital input. No effect on electical echoes on the wires at all.

If you have a borderline broken device, then you may observe it
only working on the cable end. However if you have a correctly
working device it must work in both positions, regardless of
whether another device is present. (Disregarding the CS/jumpers
issue for the moment.)

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Arno Wagner" wrote in message
In comp.sys.ibm.pc.hardware.storage Jeff Richards wrote:
Your comments are confused. There's no such thing, in SCSI or IDE, as a
terminated or unterminated device. There's a device, a terminator, or no
device. The terminator is a cheap way of pretending some sort of device is
connected, and it's important for SCSI mainly because of the cable lengths
involved. It doesn't really matter for IDE because the impact of an
unterminated connector on the signal quality (ringing, overshoot) is much
less with the shorter lengths involved, and the IDE interface can cope with
it. But there is still a difference in signal quality between an IDE cable
with a device connected and one without.

An 'Inactive' IDE device is not particularly high resistance, and certainly
has an impact on signal quality compared with an open connector.

SCSI is complicated today.

No it isn't, just complicated for you.

U2W cables are actively terminated.

No, they aren't. Ultra SCSI and LVD buses are actively terminated.

Older standards allow terminated devices (i.e. devices with internal
termion) as well as external terminators.

You got that backwards too.


As it turns out UDMA capable devices has some sort of half-assed
device terminaton,

No, they have series termination.

i.e. _every_ device on the bus has some pull-up or pull-down resistirs.

Quite inelegant IMO.

Quite elegant actually and no one cares OYO. Least T13.


Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

But that's the point. While the device might incorporate a terminator, that
doesn't make it a terminated device. If the terminator is enabled then it
becomes a device plus a terminator - exactly the same as a device with a
pass-through connection and a terminator plugged into the end of the chain.
It's a fine distinction, but unless you make it clear then you will make the
mistakes apparent in your comments, confusing what a device does in terms of
line impedance etc with what a terminator does. They are different things
and they have different effects.
--
Jeff Richards
MS MVP (Windows - Shell/User)
"Arno Wagner" wrote in message
...
In comp.sys.ibm.pc.hardware.storage Jeff Richards
wrote:
snip

SCSI is complicated today. U2W cables are actively terminated. Older
standards allow terminated devices (i.e. devices with internal
termion) as well as external terminators.

As it turns out UDMA capable devices has some sort of half-assed
device terminaton, i.e. _every_ device on the bus has some pull-up
or pull-down resistirs. Quite inelegant IMO.

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

In comp.sys.ibm.pc.hardware.storage Jeff Richards wrote:
But that's the point. While the device might incorporate a terminator, that
doesn't make it a terminated device. If the terminator is enabled then it
becomes a device plus a terminator - exactly the same as a device with a
pass-through connection and a terminator plugged into the end of the chain.

Unfortunattely that is not true.

It's a fine distinction, but unless you make it clear then you will make the
mistakes apparent in your comments, confusing what a device does in terms of
line impedance etc with what a terminator does. They are different things
and they have different effects.


A device-integrated terminator is at the end of the "T". A
cable attached or integrated terminator is at the end of the bus.
The two things coincide if the cable end-connector is attached
to the terminated device. Otherwise they do not.

And, yes, a device-integrated terminator turns a device into a
terminated device. A cable attached or cable integrated terminator
creates a terminated cable. It is a difference and it may be important
for fast buses. It is critical if there are terminated devices in the
middle of the bus, like ATA UDMA termination does.

Arno

Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
 

"Jeff Richards" wrote in message
But that's the point.

What point, topposter.
Not only do you not have a point you allowed babblemouth another opportunity to add to the confusion once again.

While the device might incorporate a terminator, that doesn't make
it a terminated device. If the terminator is enabled then it becomes
a device plus a terminator - exactly the same as a device with a pass-
through connection and a terminator plugged into the end of the chain.

It's a fine distinction, but unless you make it clear then you will make
the mistakes apparent in your comments, confusing what a device does
in terms of line impedance etc with what a terminator does.

They are different things and they have different effects.

And since you didn't explain what the difference is no point was made.


In comp.sys.ibm.pc.hardware.storage Jeff Richards
wrote:
snip

SCSI is complicated today. U2W cables are actively terminated. Older
standards allow terminated devices (i.e. devices with internal
termion) as well as external terminators.

As it turns out UDMA capable devices has some sort of half-assed
device terminaton, i.e. _every_ device on the bus has some pull-up
or pull-down resistirs. Quite inelegant IMO.