6502/Z80 speed comparison (was MITS 2SIO serial chip?) - test-drb@ccmp.vtda.org

22 Dec 2001

The most common reason for not using an hll is that unless the compiler
is well written and optimizing you see the compiler not the cpu.

Small C was a good language but the result was often so poor that
even a small amount of hand optimization was easy to accomplish.
For a cpu like 6502, this tended to be more true as many of the
things the C language likes just dont map to cpu instruction set
that directly.  Same was true for most of the Z80 versions of
small C as most treated it as an 8080 and didnt use the more
useful instrucitons.

As tot he PDP-11 that was the consumate C machine at the
instruction set level.

Allison

-----Original Message-----
From: Ben Franchuk &lt;bfranchuk(a)jetnet.ab.ca&gt;
To: classiccmp(a)classiccmp.org &lt;classiccmp(a)classiccmp.org&gt;
Date: Saturday, December 22, 2001 9:40 PM
Subject: Re: 6502/Z80 speed comparison (was MITS 2SIO serial chip?)

...
 Richard Erlacher wrote:
>
> Let's leave compilers out of the equation.  Even the same small-C
compiler,
...
 > targeted at the two quite different CPU's
potentially represent a significant
...
   skew in favor
of one or another of the two.

 Dick How can you have skew?  That is the whole idea of benchmark is to
compare
two machines. I would expect that the simple C that was given would be a
good test
when judged with other benchmarks. The 8080/Z80/8086 all generate the
same poor
code. This surprised me as shows how poor the 16 bit intel product was.
The PDP-11
version was rather nice but it even has a few quirks.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
PS. Note all my FPGA machines generate nice 'Small C' code and have a
resonably orthogonal instruction set. The well hacked Small C compiler
self compiles under
24 KB. A similar compiler for the 8080 is about 48KB. 