Re: Wozniak vs Jobs

[supertimer@aol.com (Supertimer)]

jerryp@__Mmmmunch__.ziprobes.com (Jerry Penner) wrote:

>regnirps@aol.com (Regnirps) wrote:
>>Emulation of a 1 MHz 65C02 is trivial.
>
>Well, has it actually been done?  Or is this just hypothetical?

There was a prototype ARM A2...

>For one thing, lots of 65c02 instructions execute in 2 clock cycles.  When 
>you're building an emulator, you've got to do a few other things besides 
>just map opcodes from one CPU to another.  When emulating an 8-bit CPU's 
>arithmetic, it doesn't matter all that much if you can do 32-bit 
>calculations, you still have to emulate the 8-bit ones 8-bits at a time.  
>Basically, I think it is realistic to suggest that the 6 MHz ARM could run 
>2-4 times as fast as the 6502 at the same clock speed, giving a 12-24 times 
>speed increase at 6x the clock speed.  If your CPU emulator can guarantee 
>you have only 12-24 instructions to execute in order to emulate one 6502 
>instruction, great!  It also depends on how memory and I/O is emulated.  
>These things are usually fairly expensive.  I suppose Apple could have 
>developed some hardware that would help this out.  On a pure software 
>emulator, I think you must be dreaming.

Remember that the ARM A2's ARM processor only had to emulate the
6502, not the entire A2.  Apple had hardware help with emulation of the
actual A2 design....

The Apple IIGS' 65C816 can hardware emulate a 65C02 at the same
speed, but do you really think it could achieve such great A2 emulation
without special hardware?  Most of the Apple IIGS motherboard is an
entirely new computer...Apple packed the Mega II and FPI into there
just to help with hardware emulation of the older A2s.

The PowerMac can emulate a 68k Mac, but it is not emulating the
ENTIRE 68k Mac hardware...much of the hardware is the real thing.
It does not have to emulate ADB or serial ports or disk drives, etc.

If you look at it this way, the ARM could easily have handled the
6502 emulation core which worked in REAL hardware to provide the
flawless A2 emulation speed...

Contrast this to software emulators without hardware help -- like the
GameBoy emulator for the IIGS.  The GameBoy emulator is not
just a mere 4Mhz Z80 CPU emulator.  If that were the case, the
emulator would be out NOW.  Instead, the author has to work on
I/O, graphics, sound, and other hardware specific emulation.  The
GameBoy emulator needs a fast accelerated GS to run at the real
speed as a result...(Z80 typically needs at least 5 cycles to run a
single instruction)...