Re: IIGS Acceleration Idea

Bryan Parkoff wrote:
"Ed Eastman" <noone@xxxxxxxxxxx> wrote in message news:drl9kf$7rr$1@xxxxxxxxxxxxxxxxxx

Greg Andrzejewski wrote:

A stock GS has a "slow" mode at about 1 Mhz and a "fast" mode at 2.8 MHz. What is preventing us from simply making this "fast" mode something like 10 MHz?

In a word, the FPI/CYA chip. This is the thing that times and actually does everything, from the ram refresh to the slot timing to the mainboard and slot RAM addressing. To speed up the IIgs you'd have to implement a new CYA chip to produce all the timing and address signals for the main board plus the faster clock for the IIgs.

How to accelerate your IIgs without recreating the wheel:
1. Overdrive: Replace the CPU with a high speed CPU and simple 20x clock circuit. Monitor the Speed softswitch, and the HIGH pulse of the CPU clock along with the 'internal cycle' signals off the CPU. Turn those signals into drive for overclock circuit. Each internal cycle will be then 1/10 the normal time and be ready for the next activity at normal speed. Shoudl be 100% compatible and break nothing.

2. Freewheeling 65816: A little more complex, 100% compatible. Add fast CPU, clock, Ram and refresh circuit. Additional circuit to monitor the low clock pulse to 'freeze' the CPU to obey the FPI/CYA. Obviously circuit to route and clock Bank 0/1 (E0/E1) and Rom and Softswitches to main board, run the rest in the CPU RAM.

3. Reinvent the wheel, er IIgs mode: Build the same thing but instead of freezing the CPU on low clock from main board, ignore the main board completely except for: video ram updates and slot access. Monitor speed softswitch, Rom access, Softswitch access, drive activity, downshift/ sync to main board clock as necessary. aybe load ROMs to RAM and eliminate rom slowdown.

Want a block diagram? Want a wiring diagram? Can your read minds? THen nevermind.

Thankx,
Ed



Ed,

I have to say -- do 1 GHz (GigaHertz) crystal osc chip exist? If so, you will have to redesign Apple //e or Apple IIgs motherboard. 65816 CPU will run at 1 GHz. One GHz crystal osc is divided by two or four to handle RAM as DIMM (533 MHz or beyond?). Then 1 GHz is divided by 75 (Yes, it is seventy-five) to handle video at 14MHz to support NTSC TV and monitor.
You have to find some ways to work with sound, floppy drive, etc that they only handle at 1MHz while 3.5" floppy drive and other devices handle at 2.5MHz. You would need to use DMA to prevent from CPU and video scanner sharing the same RAM like real Apple //e and Apple IIgs have. If it does not work, you will need to design a special chip which it allows to delay video and other devices until CPU is processing million cycles (less than 1 GHz) before video can be resumed to process in turn.
Michael Mahon and other folks said that it is impossible, but you have to understand how timing generator works. It is what "Understanding the Apple //e" manual explains everything how timing generator works.
I wish that it would WORK when you reinvent Apple IIgs' design of motherboard. If it does work, I can say that it is faster than Pentium IV 2-4 GHz. 

I was going to let this pass, but since you "quote" me I'll respond.

Nothing that doesn't violate the laws of physics is impossible.  What
I said was that it is not possible to just speed up the clock and have
anything workable.

I would regard a 1GHz 65816, if it were built, as a curiosity--and a
ridiculous use of transistors.

What are you trying to do?  Do you regard is as necessary to "destroy
the Apple II in order to save it"?

Of course an Apple IIgs could be completely redesigned to run at
gigahertz-speed, but that doesn't mean that it would be useful,
or that it should be done, or--and this is the critical point--
that it ever will be done.

There is no existing Apple software that does not run "acceptably"
with a conventional accelerator, and there will never be any software
for the Apple that requires gigahertz speed.  This is a fantasy.

(BTW, gigahertz clocks are generated by phase-locking to a lower
speed crystal.)

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."
.

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