Re: What's the IIe's--Arghh!--MHz Speed?

[alvin7855@my-dejanews.com]

In article <19990117135402.24395.00002805@ng-fa1.aol.com>,
  supertimer@aol.com (Supertimer) wrote:

> The important thing to remember about Apple II speed is that the
> Mhz are unique to the 65Cxx family of CPUs.  These processors,
> starting with the 65C02, are sometimes considered early RISC chips.
> Compare a 65C02 to a Z80 or an 8088/8086, for example, and you
> notice that for some instructions, the 65C02 can execute in as little
> as a single CPU cycle whereas the Z80 or 8088/8086 takes 4 or
> more.  Thus, realistically, that 1Mhz IIe runs as fast as the original
> 4.77Mhz IBM PC.

Not that this is relevant or anything, but z80 cycles are the way
they are to make it easy to build around.  The compensation for using
a three cycle memory access rather than a single cycle access, for
example, is that the z80 could be clocked twice as fast as the 6502.

In most simple applications, I (actually I should say people in my group)
have found the 6502 to be twice as fast as the z80 at the same clock speed. 
Given the 2:1 clock ratio, that makes them about the same speed.  The z80
shows more speed with compiled languages (implementing stack frames in main
memory using 16 bit index registers) and with applications that make
extensive use of pointers. It's also very kind to recursive algorithms and
reentrant subroutines.


Alvin

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