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



 
 
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  #21  
Old March 10th 06, 03:22 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 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

  #22  
Old March 10th 06, 03:38 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 ) ?

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."



  #23  
Old March 10th 06, 03:54 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
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.


  #24  
Old March 10th 06, 03:59 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
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.


  #25  
Old March 10th 06, 08:02 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 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

  #26  
Old March 10th 06, 08:04 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 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

  #27  
Old March 10th 06, 09:52 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 ) ?

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



  #28  
Old March 10th 06, 10:58 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 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
  #29  
Old March 10th 06, 02:59 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 ) ?

Folkert Rienstra wrote:

AFAIK


Which is zip.


LOL

  #30  
Old March 10th 06, 06:31 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 ) ?

"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

 




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