8-bit IDE

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Mon Apr 17 08:12:30 2000

> You've lost me, Allison. How did you "try it out?" There's a bit that has
> to be set in one of the registers to make the drive use and 8-bit interface
> rather than the usual 16. No amount of fiddling with the drive will change
> that. It either does it or it doesn't, and I've sent email to several
> makers of IDE drives, referring to the standard and asking how their drives
> handled that paragraph in the standard. Of course you'd have to look up the
> standard that prevailed at the time the drives were made.

Took my existing 16bit interfaced IDE and wrote a pattern in sector 0,
head 0, cylinder 0 or 0->ffh repeatedly till I filled the sector. Then I
disabled the word translation logic, tried setting the bit in a read op
and I got 0,2,4,6.... didn't work.

> > Well wishful thinking had me check it out using several 85-130mb drives
> > (quantum, Seagate, maxtor, WD) and none seem to do that. After all
> > having that would make the interface a no brainer and save a simple silo
> > for splitting read and writes. However, it was wishful thinking.
> >
> What???

I tried to interface using only 8bit data and using the 8-bit IO bit and
it didn't work. It was wishful thinking I could use it.

> I personally like the CMOS much better since it drives harder, and since it
> pulls and pushes with the same impedance, unlike TTL which sinks 16 and
> sources 1.6 mA. I've tried replacing all the bus interface buffers on my
> old S-100 cards with AC logic. In some cases I used HC or AHCT (SAMSUNG)

I've seen latchup on busses that ring negative using HC and HCT parts.
I'd like the better drive but they would randomly flame on me due to the
bus ringing. Obviously loading the bus with terminators would solve this
but it's still something that worried me and made for a less robust card
for handling and ESD.

Allison
Received on Mon Apr 17 2000 - 08:12:30 BST