Whats the difference between Adaptecs...

[Keith Pyle]

In article <1991Jan5.045321.1799 at sp90.uucp> sanand at sp90.uucp writes:
>> 	Can anyone tell me what the difference is between Adaptec's 1542A and
>> 1542B SCSI controllers is?  I am planning on using one of them in an ACMA
>> 386/20 system with a Maxtor SCSI drive.  I have heard of problems with the bus
>> Kevin W. Rudd
>> Sequent Computer Systems
>> 
>
>I am not sure of all the differences, but the major one is that "B" has
>a floppydisk controller, "A" doesn't. I run the "B" with a Maxtor, so far
>(touch wood) no problems.
>
>Sanand.

This isn't quite correct.  The 1542B is a newer model of the 1542A and is
a two-thirds length card instead of the full-length used for the 1542A.
Both the 1542A and 1542B are intelligent controllers which support floppy
as well as SCSI drives.  The floppy portion can be disabled by a jumper,
if desired.

If I remember correctly, the 1540 series is the SCSI only controller (i.e.,
no floppy).  Whether there are A and B versions of it, I'm not certain,
but I think there are.

The 1542A and B are supposed to be functionally identical, I believe.
However, I have one machine running a 1542A in a 286 that works fine
with Fastback 2.01.  Just toying around with a 1542B in the same
configuration, I found that the system would hang during the DMA tests
that Fastback runs (specifically, the medium speed DMA check).  I
haven't had the time yet to really run this down.
-- 
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Keith Pyle                                UUCP: ...!cs.utexas.edu!execu!keith
Execucom Systems Corp., Austin, Texas     Internet: keith at execu.com
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