andrel wrote:

> Neither the 6510 nor the Z80 had a floating point processor. Floating 
> point was in software.

That's true. But assuming we want, say, a normal "double precision" 
floating point number, how many clock cycles would you estimate it takes 
to operation on? A dozen? A hundred?

> Both had a variable instruction set that took a variable amount of 
> cycles to execute and therefor the number of instruction processed 
> depended on the program and especially on the addressing modes used.

I thought this was true for *all* processors?

(Of course, unlike modern processors, cache effects are not present.)

> although the MIPS rate is not very well defined, on average it 
> may be in the order of 1/3rd of the clock speed for 65xx and 1/5th-1/4th 
> for Z80.

Sounds roughly right. (For the 65xx anyway - I have a manual somewhere 
that lists all the opcodes and addressing modes...)

So that gives us, very approximately,

- C64 = 1.0 MHz / 3 = 0.333 MIPS.
- ZX Spectrum = 3.5 MHz / 4 = 0.875 MIPS.

So each is giving us probably a few hundred thousand complete opcodes 
executed every second.

Now, anybody have any clue "how big" the numbers are for less ancient CPUs?

-- 
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