6502/Z80 speed comparison (was MITS 2SIO serial chip?)

From: Richard Erlacher <edick_at_idcomm.com>
Date: Fri Dec 21 19:48:17 2001

Nobody really cares, but it's certainly not reasonable to argue that, because it
has a Z in it's name, the Z180 or Z280, or whatever, is a Z80.

I once involved myself in a pretty thorough evaluation of 6502 and Z80 and found
that it's difficult as hell to conjure up a test that really compares the two on
a strict basis of performance. Most manufacturers essentially rated their
processors on the basis of how many NOP's they could execute in a second. It
seems silly, but it's probably as good a yardstick as any for establishing
relative speed. However, that definitely gives the 6502 an advantage, and we
wouldn't want to disadvantage the venerable old Z80, since everybody knows it's
faster than the 6502, right?

Anybody who gives this comparison any thought will quickly realize that it's not
an easy pair to compare. In reality, there was a MUCH larger software base for
the Z80, so many tasks would still be waiting to be coded, even today, but for
the fact that they'd already been done for the 8080, the code for which runs
without modification, in most cases, on a Z80,.by the time the 6502 became
popular. Now, I've always believed the 6502 at 1 MHz to compare favorably with
the 4 MHz Z80, but I used the Z80 running CP/M 2.2 to do useful work, since it
was a lot more trouble squeezing useful work out of a 6502 back in '78-'79.


----- Original Message -----
From: <CLeyson_at_aol.com>
To: <classiccmp_at_classiccmp.org>
Sent: Friday, December 21, 2001 5:34 PM
Subject: Re: 6502/Z80 speed comparison (was MITS 2SIO serial chip?)

> Come on guys cool it. Who really cares if a Z80 is faster than a 6502 ?
> I sure as hell don't.
> For those who are interested check out the following:
> US Patent 4004281 Microprocessor Chip Register Bus Structure (6800)
> US Patent 4332008 Microprocessor Aparatus and Method (Z80)
> US Patent 3991307 ...on the fly correction to provide decimal results (6502)
> By the way, the 6800 Patent has complete circuit diagram.
> The Z80 also contained DRAM refresh circuitry that the 6502 didn't.
Received on Fri Dec 21 2001 - 19:48:17 GMT

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