Re: 18 Mhz IIgs?

[Rubywand <rubywand@swbell.net>]

Charles writes ...
> 
> Ok, I'm scanning the Apple II websites and I run across this one:
> 
> http://applemuseum.bott.org/sections/computers/IIgs.html
> 
> A quote on this page says:
> 
> The Apple IIGS was, and still is, the most impressive Apple II ever
> produced. They were introduced in September of 1986, and ran a much
> better processor, the Western Digital 16-bit 65C816 (compatible with
> 6502) running at 2.8 MHz. With third party hardware it can now go up to
> 18 MHz.
> 
> What?  Who is running a IIGS that fast?


     Someone may be. The current 65c816's are supposed to be good for 20MHz.

     On a IIgs, getting up to 16MHz could happen with someone using a newer
version of the 65c816 on a TransWarp-GS or ZipGS accelerator board equipped
with a 64MHz oscillator module and faster than usual RAM and, possibly,
higher-speed versions of one or two 74xxx IC's.

     The main limitation seems to be that (besides RAM) the IC's and other
components on the accelerator boards do not all perform correctly as you push
the speed. Layout of traces could also be a limiting factor. Since some
boards handle a speed boost better than others, it's hard to come up with
reliable speed upgrade cookbooks.

     Most TransWarp-GS or ZipGS accelerator boards seem capable of 10MHz
operation with fairly minor changes. At 10MHz a TransWarp-GS with 7K cache
gets about a x2.5 system speed increase over standard "Fast" IIgs operation
(2.8MHz). With the 32K cache, you go to about x3.25. ZipGS specs are similar.

     Once you're running around 10MHz, you have a IIgs which feels and works
much like your modern PC or Mac. For instance, delays for opening volumes and
folders in the Finder mostly vanish, games like Dungeon Master and various
super-res utilities don't feel sluggish, etc..

     Probably, especially with the new 65c816's, more IIgs users could run
their accelerators at 15-16MHz or higher; but, you are talking about,
potentially, quite a bit of extra bother to get a relatively small
performance boost above 10MHz.



Rubywand