Re: DMA 4 meg v. 8 meg

[Michael J. Mahon <mjmahon@aol.com>]

Charlie <charlieDOTd@verEYEzon.net> wrote:
> On 5/5/2011 1:21 AM, David Empson wrote:
>> 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?
> 
> The Carte Blanche card.  As for how likely they are to be used on a IIgs,
> I might be the only one.

I thought the JAT firmware only eavesdropped--no DMA...

-michael  -  NadaNet 3.1:  http://home.comcast.net/~mjmahon