<21688 at scuzzy.mbx.sub.org>

[Heiko Blume]

neese at adaptex.UUCP writes:
>Software cannot override this jumper.  This jumper simply indicates who will
>attempt to negotiate for synchronous protocol.  If the jumper is installed the
>AHA-154x board will negotiate for it, if the jumper is removed the adapter
>expects the device to negotiate for it.  I would allow a device to do the
>negotiation as some devices will do the negotiation on each data transfer.
>If the 154x does the negotiation, it will only be done once.

very interesting, someone from ISC posted, that with 2.0.2 the software
switched the negotioation off...

>>>With BUSON 5, BUSOFF 9 and DMASPEED 0; the system seems to be
>>>performing just fine. 
>>
>>sure, these are the 'works 100%' parameters. not the 'works 100% and
>>performs 100%' paramters.

>The system will perform with these paramters, but not they are not the
>optimum values.  It actually takes some experimentation to find what is
>best for any given environment.  The variables that come into play are
>the device(s) connected, the size of any given data request, and the
>actual speed data can be transfered across the AT bus.

one should be *very* careful while experimenting! i have an informtech
386 33Mhz board and a 1542A. when i set DMASPEED to 1 (6.7MB/s) all ran
fine, but not for long... after some time (several days) i got
'unexpected NMI in system mode' (of course during fdisk updating the
partition table on my 600MB disk when i wanted to activate the DOS 
partition. it wiped out the fdisk table, VTOC etc...). after installing
on other disks parity errors started to show up along with the NMIs (
always in the 5th MB). of course i can run ram tests forever without any
errors. the NMIs are also not only popping up on my (personal) board,
other people with that informtech board have the same problem.
but now for the fun! my friends machine is *identical* to mine, and guess
what? he runs at 6.7MB/s happily all the time. the difference is: he
runs xenix and i run interactive... (all those people that told me, that
they got NMIs too run interactive). looks like a software problem,
doesn't it? (of course i ran the DMA test on the aha, no problems).

for completeness the config is
informtech 386DX 33MHz board with
  4 MB 70ns rams on board
  4 MB 70ns rams on 32bit ram card
  BUS speed set to 12 MHz (had to put in pins for jumpers,
  might that cause the problem? since you say that the DMA is independant
  of the bus speed i don't think so, and i *wont* try out....)
adaptec aha-1542a (ST296N, pro80-s, 94181-702 drives)
hercules mono with parralel port
dumb 2 port serial card

-- 
Heiko Blume c/o Diakite   blume at scuzzy.in-berlin.de   FAX   (+49 30) 882 50 65
Kottbusser Damm 28        blume at scuzzy.mbx.sub.org    VOICE (+49 30) 691 88 93
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