Re: 8 MB GS RAM cards with FOCUS& Zip GS

[CUTjefbla@bconnex.net (Jeff Blakeney)]

On 13 Jun 1998 18:47:10 GMT, joreilly@smtp.dorsai.org (James OReilly)
wrote:

>I've been assured that I'd encounter no problems using an 8 Meg RAM Sirius
>expansion card on my ROM 01 Apple IIgs together with a FOCUS HD card, as
>the FOCUS is not a SCSI device, and DMA (whatever that is) is not
>involved.

Just for your information, DMA stands for Direct Memory Access.  It
allows an interface card in your Apple II to disable the processor
(the 65816 in the case of a IIgs) and get access to all of the memory
in the system.  This allows the interface card, a hard drive
controller in this case, to move data directly from the hard drive to
the proper location in memory.

This gives much faster performance than not using DMA because without
DMA the processor must take the data from the interface card and put
it in the proper location in memory.  This extra step takes more time
which slows down the transfer.

>I then read that if I got an 8 Meg RAM card, I could experience a short or
>overheating due to the card's contact with the lid, or to its proximity to
>other cards.  Isn't the 8 Meg Sirius card the same as the 4 Meg Sirius
>card except that it is fully populated?  If both cards are the same size,
>why should I experience problems with the 8 Meg card which I wouldn't
>experience with the 4 Meg card?

If the 4 MB card and the 8 MB card are indeed the same, then you
probably shouldn't run into any problems.  However, some cards can
start to warp when they are fully populated.  This happened to mean
with my CVTech 4 MB RAM card.  When I fully populated it, I needed to
put a spacer between it and my Apple 1 MB RAM card that I had in the
piggy back slot to keep them from touching each other.

I also had to put a piece of cardboard between the Apple card and the
side of my IIgs case to keep the card from shorting out on the RF
shielding.

As long as you are careful and you don't bang your IIgs around a lot,
then you shouldn't need to worry too much.  If things look to be too
close together, just put something non-conductive between them to be
sure they don't come in contact with each other.

>Would the above 8 Meg Sirius RAM card & FOCUS HD work with a ZipGS
>accelerator, if one were ever to be found? 

I don't know if the ZipGS would be able to do DMA into all 8 MB of the
Sirius RAM card or not.  You'll have to get someone else to answer
that one.

=== I've had enough SPAM.  Cut the obvious from my address to email me. ===
         Jeff Blakeney - Dean of the Apple II University on Delphi