Re: looking for souping hardware

[spector@vax2.concordia.ca (Mitchell Spector)]

In article markm@winternet.com (Mark Miller) writes...
>
>In article <27MAR199622155378@vax2.concordia.ca>,
>Mitchell Spector <spector@vax2.concordia.ca> wrote:
>>
>>	Good question. I now know that Sequential's RAM GS Plus
>>(formely CV-Tech's CV-RAM board) is _not_ DMA compatible in a 6, 7 
>>or 8MB configuration with a RamFAST as claimed.
> 
>Please elaborate.  Why is it not DMA compatible above 5Mb?

	Due to a design limitation, the Apple IIgs can only DMA
the first four megabytes (4096K) it finds in the memory expansion
slot. The reason for this is lack of a third special pin in the
socket, something Apple left out for some odd reason. This however
does _not_ include memory built-in on the motherboard, this is why
a ROM 01 (256K) can have a total of 4.25MB of DMA memory while a
ROM 3 (1152K) can have 5.125MB of DMA memory.

	Some memory boards were suppose to "trick" the IIgs into
being able to DMA all memory beyond 4MB, but apparently it didn't
work so well. CV Technologies claimed with their CV-RAM board in
combination with their RamFAST SCSI could DMA up to a full 8MB. 
Apparently though, people who've tried this say files copied from
one hardrive partition to another are corrupted unless they disable
DMA on the RF SCSI (which of course slows things down). Alltech just
released a new 8MB board called the Sirius RAM...perhaps we'll have 
better luck with that.

>Mark Miller         | "The things that pass for knowledge I just
>markm@winternet.com |   can't understand." - Steely Dan

Mitchell Spector
spector@vax2.concordia.ca