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From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.sys.apple2
Subject: Re: DMA SCSI card
Message-ID: <13118@smoke.BRL.MIL>
Date: 14 Jun 90 19:26:17 GMT
References: <9006141515.AA13853@apple.com>
Organization: U.S. Army Ballistic Research Laboratory, APG, MD.
Lines: 31

In article <9006141515.AA13853@apple.com> SOMCYC@NUSVM.BITNET (Chiang Yao Chye) writes:
>1.  Is the Applied Engineering GS-RAM plus card *REALLY* DMA compatible?
>    Is it only DMA compatible to 4 megabytes, or compatible to 6 megabytes?

I don't own a GS-RAM so I'm partly guessing, but
	(a) I don't think a 6MB configuration should be expected to work
	at all, due to the way the IIGS addresses memory;
	(b) I doubt that any RAM expansion card would be DMA compatible
	beyond 4MB, but this is not an issue for the High-Speed SCSI Card
	since it (or at least the GS/OS driver) doesn't use DMA beyond
	the lower 4MB anyway.
	(c) Early GS-RAMs were not DMA compatible, but an upgrade is
	available from AE.  Recent GS-RAMs are supposed to be okay.
	A way to find out whether yours is is to boot GS/OS with the DMA
	switch ON on the High-Speed SCSI Card, and if it crashes (probably
	near the end of the boot thermometer) try again with the DMA
	switch OFF.

>2.  The older formatting/partitioning programs, specifically SCSI Hacker
>    and Vanilla, do not work with the new DMA SCSI card.  This is a loss,
>    because these 2 programs can set the interleave factor when the hard
>    disk is being formatted, whereas the SCSI Utilities that are supplied
>    with the card cannot.  So, is there a way to set the interleave of
>    the drive by any other means, or is an upgrade to SCSI Hacker or
>    Vanilla available to work with the new card?

The Chinook SCSI Utilities have the same problem.  I don't know about
upgrades; however, 1:1 interleave works well with many SCSI drives (at
least on my TWGS-equipped system).  Because of GS/OS caching, interleave
should not be of much concern, except for rare special applications such
as the Star Wars demo.