Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!convex!mic!letni!rwsys!merch!cpe!adaptex!adaptx1!neese
From: neese@adaptx1.UUCP
Newsgroups: comp.periphs.scsi
Subject: Re: Adaptec 1540B/1542B compatibility q
Message-ID: <283400111@adaptx1>
Date: 13 May 91 17:30:49 GMT
References: <9818@cs.olemiss.edu>
Lines: 29
Nf-ID: #R:cs.olemiss.edu:9818:adaptx1:283400111:000:1421
Nf-From: adaptx1.UUCP!neese    May 13 09:49:00 1991


>/* ---------- "Adaptec 1540B/1542B compatibility q" ---------- */
>
>I am interested in purchasing an Adaptec 1540B or 1542B controller to
>run DOS and UNIX (ESIX). I have been told that there are compatibility
>problems with the card and Windows 3.0 and other DOS programs.
>
>Can someone fill me in on the actual problems? (if any)

You have been misinformed.  You have a couple of options in running
Windows 3.0 with a bus master (AHA-1542B).  You can leave SMARTDRV.SYS
loaded and 3.0 will work just fine.  If you don't want to use SMARTDRV.SYS
you will need the ASW-1410 ASPI DOS Manager.

The problem is this:  A bus master needs physical addresses as it is the
card that is responsible for moving the data to/from the SCSI device and
host memory.  Windows 3.0 puts the 386 into virtual mode and thus all
memory references are no longer physical, but are logical.
SMARTDRV.SYS allocates a fixed amount of memory in lower DOS RAM whose
logical addresses also happen to correspond to the physical addresses.  Thus,
no other driver is required.  The ASW-1410 ASPI DOS Manager use the INT4B
services as defined by Microsoft in Windows 3.0.  One of these services allows
the driver to ask for a physical memory reference from the logical memory
reference, thus bus masters are happy.

			Roy Neese
			Adaptec Senior SCSI Applications Engineer
			UUCP @  neese@adaptex
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