Re: Apple IIgs RAM disk

[nathan@visi.com (Nathan Mates)]

In article <5jbav9$h5r@lynx.unm.edu>,
stephen e buggie <buggie@musca.unm.edu> wrote:
>WHAT THE APPLE WORLD NEEDS NOW is a 4 meg slot 1-7 RAM card, sort of like 
>RamFactor for the IIe.   Does such a card exist, and would its extra 
>memory be recognized in addition to the 4 megs in the RAM card slot.

   The GS has a particular method of accessing memory: all GS memory
is accessible by the processor at any time, in any order. [Well,
excluding times when DMA's going on.] Slot 1-7 ram cards are the
antithesis: memory is accessible one byte at a time in sequential
order, with a speed penalty for getting a byte that is not the 'next'
byte.

   There is a very serious and fundamenual difference between these
two types of RAM, and it's not going to be overcome anytime soon.  GS
programs are all written to assume that all GS memory is trivially and
immediately accessible (which it is), and would require a major
rewrite to make hacks for the //e work as GS Ram. If you only wanted
to do certain things, such as a ramdisk, that is a feasible use for
a slot 1-7 card.

   Blame Apple for being too shortsighted to allow >4MB of GS main RAM
at the same time as DMA, and for crippling the //e's extended memory
access after the far more flexible and usable III model, leading
people to come up with such ungainly hacks as the slot 1-7 RAM cards.


   BTW, this information is in section 4.2 of the comp.sys.apple2
Frequently Asked Questions (FAQ) at
http://www.visi.com/~nathan/a2/faq/csa2.html, "Can I add more memory
to my Apple II"

Nathan Mates

--
<*> Nathan Mates http://www.visi.com/~nathan/      <*>
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