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From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple2
Subject: Re: DMA detection
Message-ID: <1990Aug24.011911.10594@laguna.ccsf.caltech.edu>
Date: 24 Aug 90 01:19:11 GMT
References: <1990Aug23.224445.3691@utstat.uucp> <1990Aug24.003638.9617@laguna.ccsf.caltech.edu>
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Oops, what I meant to say was, it is possible for software to check the memory
configuration, but that's not conclusive. Example:

Software sees two megs in the expansion slot. DMA compatible?

Yes, if you are using a GS Sauce, GS Juice, OCTORAM w/ 2 1 meg SIMMs, ...

NO, if you are using an OCTOram with eight 256k SIMMs on it.

In general, if your card's maximum capacity is four times its minimum (with the
same given chip density) then it is almost definately DMA compatible.

If it supports more (All of AE's cards do), then the additional expansion
beyond four MAY OR MAY NOT be DMA compatible. The motherboard supports 1, 2, or
4 rows of 256K, and 1, 2, or 4 rows of 1 meg. Any other configurations are not
automatically DMA compatible.

You could do it if a DMA device was available for the test software to use.

It should be possible to write a very simple program for the DMA SCSI card that
tests all expansion RAM for DMA compatibility. I'll do that when I get mine
(soon, soon... I'm very close to a final decision on the hard drive).

Todd Whitesel
toddpw @ tybalt.caltech.edu