ac3a+@andrew.cmu.edu (Axel Cleeremans) (06/07/91)
I would like someone (from Apple maybe?) with some kind of technical
authority to clarify the confused debate about the speed of the IIsi in
256 colors mode. It has been claimed that beefing up the disk cache up
to 768K results in screen updates that are about as fast in 256 colors
as in B&W. The explanation, as I understand it, is that when the cache
is set that high, all of memory bank A is now dedicated only to video &
cache, so that applications need not share access to that part of the
memory anymore, thereby resulting in faster accesses. I tried this, and
it seemed to result in some moderate improvement in applications, but
not in the Finder. Other people have reported very significant
improvements, and yet others complain that the trick does not seem to
have any other effect than reducing the memory available to applications.
This is where it gets confusing : According to other messages
(posted mostly on infomac), the mmu is set up to map the video RAM to
high memory, so what we really need is an extension that prevents access
to *those* memory locations. According to another poster, simply beefing
up the cache results in speed increases, but only when MM init is
installed. But of course, yet other messages suggested that MM init was
of dubious value, and that at any rate, whatever problems it was trying
to fix were fixed in System 7.0.
So what is the final word on all this? Is there a way to improve the
IIsi's performance in 256 colors mode? If yes, *what* is it? I for one
would really like to know, as my si really is kind of sluggish in 256
colors.
Please post, I guess this if of general interest.
Axel Cleeremans [ac3a@andrew.cmu.edu]