On Mon, 11 Feb 2002, Julius Sridhar wrote:
On Mon, 11 Feb 2002, Tothwolf wrote:
Original - narrow, 5Mb/s [used by lots of
older devices]
Fast - narrow 10Mb/s [very common]
Ultra - narrow 20Mb/s [very common]
Wide - wide, 20Mb/s [common for a short time]
Ultra-Wide - wide, 40Mb/s [very common]
Ultra2 - wide, 80Mb/s [never really caught on]
Ultra160 - wide, 160Mb/s [starting to become common]
Ultra320 - wide, 320Mb/s [not common yet]
Ok. First of all, it's MB/s, rather than Mb/s.
*shrug*
Actually, it would have been better to type the whole thing up with 'MHz'
and bus width, instead of just MB/s, but I was in a hurry. Oh well, use
Google.
Second, MB/s is not a good way to describe the
bandwidth of the bus
for technical reasons. A fast/wide 20MB/s bus looks *nothing* like an
ultra 20MB/s bus. This is so because fast/wide is a 10MHz 16-bit bus
and ultra is a 20MHz 8-bit bus.
I didn't imply that a "fast-wide" bus was anything like the
"ultra" bus.
Just because they have the same bandwidth doesn't
mean anything. An
ultra device will run at 10MB/s on a fast/wide bus and a fast/wide
device will run at 10MB/s on an ultra bus. Both busses are *capable*
of 20MB/s.
Of course the ultra device would run at 10MB/s, a fast/wide bus runs at
10MHz, and the ultra device is only 8 bit instead of 16.
If you have an ultra device and an ultra/wide device
on an ultra/wide
bus, the ultra device will run at 20MB/s and the ultra/wide device
will run at 40MB/s *simultaneously* **on the same bus**.
I'm not disputing that.
> (info from memory, might be incomplete,
inaccurate, etc, etc)
Uhm, I did put a disclaimer in here...
There are also
Differential versions of Fast, Ultra, Wide, and Ultra-Wide.
These use a "high voltage" (+-12VDC IIRC) signaling that is *NOT*
compatible with standard devices. You will literally fry any non HVD
devices if you connect a HVD drive to the same bus. Ultra2 and newer have
a Low Voltage Differential bus, I'm not sure if there is a HVD
specification for those.
Signalling voltages are irrelevant to this discussion.
Actually, I think not. With the way this thread has been going, I think it
is quite a good idea to mention the differences between "standard", HVD,
and LVD signaling.
-Toth