Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!yale!hsdndev!cmcl2!adm!smoke!gwyn
From: gwyn@smoke.brl.mil (Doug Gwyn)
Newsgroups: comp.sys.apple2
Subject: Re: More on the OctoRam
Message-ID: <15416@smoke.brl.mil>
Date: 10 Mar 91 21:04:17 GMT
References: <5022@mindlink.UUCP> <1991Mar8.005356.21694@ux1.cso.uiuc.edu>
Organization: U.S. Army Ballistic Research Laboratory, APG, MD.
Lines: 20

In article <1991Mar8.005356.21694@ux1.cso.uiuc.edu> scotth@ux1.cso.uiuc.edu (Scott Henderson) writes:
>new version of the card is DMA compatible.  DMA (according to the person
>I talked to at Digital Data Express) only uses 4 megs, so the other 4 megs
>on the card (assuming a full card) will just not be used by DMA (am I 
>explaining this correctly?)

No.  DMA can occur to/from any address.  It happens that the Apple
High-Speed SCSI card does not use DMA for accesses above 4MB, but
that's not the only potential source of DMA transfers.  I explained
this is more detail in a recent posting.

Note that the Apple IIGS Hardware Reference Manual (second edition)
states that only 4MB RAM is considered supported.  In practice, at
least with a ROM 01 IIGS, one can use an 8MB OctoRAM with a little
care (as previously described).

It's nice to hear that the OctoRAM is again being manufactured.
It's a nice product.  (It's also interesting to watch the faces of
your IBM PC-owning friends when you mention that your IIGS has 8MB
of RAM, 68881 FPU, several SCSI hard disks, etc.)