mfry@enint.Wichita.NCR.COM (11/22/89)
NCR has been shipping the PC/386 (aka PC925) for several months now.
This machine uses the Western Digital FASST/7000 SCSI host adapter and
SCSI disk drives. When we first installed Windows/386 Version 2.11, we
encountered the same problems others have discribed. As noted by
someone else on netnews, the trick to getting the system to work was to
load a special memory resident driver which I believe replaces some, if
not all, of the host adapter's BIOS ROM. To decrease this driver's
memory requirements, which was necessary to get a lot of our software
to run without crashing, we used the following config.sys entry:
device=sstbio.sys /WE/B:0
The "W" option tells the driver to handle virtual to physical memory
mapping (the key to getting WIN386 to run.) The "E" option tells it to
use a 16KB buffer for these translations rather than the default 64kB
buffer. The "B:0" option disables the drivers track cache buffer which
generally defaults to 16KB.
The problem is not with SCSI, but with the way some host adapters are
designed. The FASST/7000 and the Adaptec host adapters use 1st party
DMA (I believe I got the right party.) This means the adapter
generates memory addresses when transferring data rather than using the
system's DMA controller to do so or having the CPU copy data from the
adapter's buffer to memory. If properly designed, this approach can
improve data transfer rates considerably on AT bus. Other adapters
such as those shipped by Segate either use the CPU to copy data or the
system's DMA controller. Therefore Windows/386 should run with them.
Operating environments such as WIN386 and Desqview like to play games
with memory maps using the 80386's memory management unit. While I
don't pretend to understand all of the details, the end result is that
disk data gets transferred to the wrong location in system memory. The
system doesn't live long after this occurs.
While our experience with running Windows/386 on a system with the WD
FASST/7000 is somewhat limited, we have had no problems with the
systems crashing once we got them configured properly.
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| Mike Fry | Mike.Fry@Wichita.NCR.COM |
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