Re: Wozniak vs Jobs

[regnirps@aol.com (Regnirps)]

supertimer@aol.com (Supertimer) wrote:

>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....

Well said. Remember, I'm not making this up. It was all done and proven by
ACORN for the ARM (originally ACORN Risk Machine) add ins for the 2 MHz 6502 
BBC Computer ten years ago.

Charlie Springer