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



 
 
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  #11  
Old March 9th 06, 08:18 PM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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*
  #12  
Old March 9th 06, 08:35 PM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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*
  #13  
Old March 9th 06, 08:52 PM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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.


  #14  
Old March 9th 06, 09:02 PM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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."
  #15  
Old March 10th 06, 01:11 AM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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

  #16  
Old March 10th 06, 01:13 AM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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*

  #17  
Old March 10th 06, 02:59 AM posted to microsoft.public.win98.disks.general
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Default 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 ?




  #18  
Old March 10th 06, 03:13 AM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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
  #19  
Old March 10th 06, 03:17 AM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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
  #20  
Old March 10th 06, 03:20 AM posted to alt.comp.periphs.hdd,comp.sys.ibm.pc.hardware.storage,microsoft.public.win98.disks.general
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Default 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

 




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