ISA SCSI adapters - summary of replies

[Andrew Herbert]

Here is a summary of the information I received regarding AT bus scsi cards.
Many thanks to the people that replied.

This summary gives info on the following cards:
	Adaptec AHA1540B/1542B
	DTC 3280A
	Future Domain TMC830
	Western Digital WD FAST-ATXT
	Western Digital WD 7000-FAST

I have not included prices, but the above cards are priced in the approximate
range of US$150 to US$550.  My guess is that the WD ATXT is the cheapest,
followed by DTC and Future Domain, then Adaptec and finally the WD 7000
(the most expensive).

All things considered, Adaptec seems to be the way to go.  However, all of
the cards mentioned are most likely very good except for the WD FAST-ATXT.

Cheers,
Andrew
---
Adaptec AHA1540B/1542B
----------------------
* Maximum SCSI->AT transfer rate: 10M bytes/s (motherboard-dependent).
	(Bus master DMA, => card drives bus directly, not via the PC's DMA
	controller.)
* Synchronous transactions (i.e. scsi-2) supported.
* Onboard cpu handles SCSI protocol and allows the card to be used like a
standard MFM controller (presumably at the BIOS level) by mapping between
physical and virtual disk geometries (e.g. sectors/track, number of cylinders).
* Onboard BIOS provides OS compatibility (well, DOS at least :-); SCO Unix,
Interactive Unix and Esix support the controller through standard drivers.
* The 1542B is the 1540B plus floppy support.

DTC 3280A
---------
Little is known about this card, except that it works with DOS without any
special drivers.  It includes floppy support.  The installation guide states:
"All SCSI devices that conform to the American National Standards Institute
(ANSI) X3.131-1986 and Common Command Set (CCS) Rev. 4b specs are supported
by the DTC31/3280A".  Maximum throughput is >= 800k bytes/s (obtained
using Seagate ST4376N with a 20MHz 386).

"The only problem I have had is that the floppy disk drives only seem to
recognise the first media density type you use after bootup i.e. if you put
a high density disk in the drive, it will then not work with low density
disks (they both used to work as the floppy drives are dual density).  I'll
probably have to go back to the dealer on that one.  Apart from that I'm quite
happy."

Future Domain TMC830
--------------------
ISC (e.g. Interactive Unix) supports this controller.

Western Digital WD FAST-ATXT
----------------------------
"The WD FAST-ATXT controller is a dog."
* No intelligence, device driver required for DOS.

Western Digital WD 7000-FAST
----------------------------
>From comments on the net, this card is roughly equivalent in performance to
the AHA1540B.  There is doubt as to whether the driver for Interactive Unix
2.2 actually works.