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.