Re: ROM 3 IIgs, SCSI cards, and DMA

[dempson@actrix.gen.nz (David Empson)]

Jason Whorton <jason@microxl.com> wrote:

> Hello.  I have an Apple High-Speed SCSI Card in my Apple IIgs ROM 3.  I am
> considering the purchase of a Sirius RAM card.  The FAQ says that if I had
> 8MB of RAM on it, I would have to turn off the DMA.  How much RAM could I
> install on it and keep the DMA turned on?

4MB in the memory expansion slot is the limit to retain full DMA
compatibility.

> Which would be better, 8MB of RAM and DMA turned off or using DMA and the
> maximum amount of RAM that can be used while keeping the DMA turned on?

Unless you need a huge amount of RAM for some reason, I'd suggest 4MB
(5MB once you include the motherboard RAM) with DMA.  The speed benefit
of DMA is very significant.

(This is the configuration I used.)

>     How much faster would my IIgs system be with a new 1MB RAMFast SCSI card

The extra RAM won't help the machine's speed, and the RamFast is
generally faster than Apple's High Speed card anyway.

Do you actually need the extra 3MB of RAM?  (With the ROM 3, only 7MB of
the card RAM is accessible, so you would get 8MB in total, not 9MB.)

If not, I'd suggest that you should save your money by getting a 4MB
card.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand