Re: DMA 4 meg v. 8 meg

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

Michael Black <et472@ncf.ca> wrote:

> On Wed, 4 May 2011, KP wrote:
> 
> > I have a 4 meg RAM card in the memory slot of my ROM 03 IIgs.  I have
> > often heard that only the first 4 megs of expansion-card RAM is DMA-
> > compatible.  Can somebody explain what DMA actually is?
> >
> > Does this mean that AppleWorks v5.1 will only recognize 5 megs (1 meg
> > motherboard RAM + 4 meg expansion card RAM) even if I put an 8 meg
> > expansion RAM card in the memory card slot?
> >
> > Does this mean that the second 4 meg of expansion card RAM is useful
> > only as a RAM disk, and not as memory for programs to access, in order
> > to store long documents that the user is editing, graphics being
> > opened from disk, sounds being edited, HyperStudio stacks, etc.?
> >
> I see the specific question wasn't answered.
> 
> It won't mean a thing for your purposes.
> 
> Unless you have something that takes control of the Apple bus in order to
> directly control the RAM, lack of DMA won't matter to you.

And for a IIgs, the only cards I can think of which use DMA are the
Apple High-Speed SCSI card, and the RamFAST SCSI card. If you don't have
either of them, you don't need to worry about DMA.

Is anyone else aware of any other DMA-capable cards that are likely to
be used in a IIgs?

(Old CP/M cards are not very compatible with the IIgs, and Apple II
accelerators don't work.)

-- 
David Empson
dempson@actrix.gen.nz