ISA bus throughput

[Chuck Guzis]

On 2/2/2006 at 6:44 AM mbbrutman-cctalk at brutman.com wrote:

>Yes, this would be interesting.  I had never realized that IDE was a
>superset of ST506.  Now I'm thinking of all of the old 8 bit machines I
have that
>could use an IDE hard disk.  I've been trying to graft SCSI cards onto
them, but 8
>bit SCSI cards with BIOS aren't exactly common either.

Careful--most recent IDE drives are not capable of 8-bit data transfers.
Commands and status are read and written from 8 bit registers, but the data
transfer part of the operation is 16 bit.  There IS an 8-bit transfer
capability defined by the ATA standard, but it was deprecated in ATA-3 and
most drives don't handle it.    There may be some old controllers around
that can do the translation, but ATA on 8 bit PC-XT was pretty rare.
However, it'd be easy to prototype up a controller.   Alternatively, you
could do much of what you wanted in software--just ignore half the sector
data and read 2 sectors when one was requested.   All in all, it'd probably
STILL be faster than the old 5.25 MFM drives.

Cheers,
Chuck