[Coco] CPU speed in MIPS

Joel Ewy jcewy at swbell.net
Mon Apr 16 10:48:53 EDT 2007

Diego Barizo wrote:
> Looking at Sock's page for Donkey Kong, I noticed that he has the
> speed in MIPS of the 6809 and the Z80.
> Curiosity made me go to the Wikipedia, were I found that the 8086 does
> 0.8 MIPS, the same as the 6809 at 1.8 MHz (further proof of the power
> of the CoCo).
> I wonder if there is a chart somewhere that compares different CPUs
> from the 70s/80s?
Hey Diego,

I'm not sure if there is any kind of definitive list like that, but the
value of such a comparison can't be much more than a very crude
benchmark.  The problem with MIPS is, "which instructions?" "are these
instructions actually used in real programs?" and "how much work gets
done by each instruction?"  OTOH, MIPS probably gives a better picture
of performance than a simple comparison of clock frequency.

It might be fun to trawl Wikipedia for such figures.

The authors of a textbook for a computer architecture class I took in
college (Hennessey and Patterson) said that the best benchmark for
performance comparison is the running time of a real program.  It would
be interesting sometime to compare the exact same program on an IBM PC
(8088 4.77MHz) and a CoCo.  A big problem with that would be that any
compilers and libraries would be unlikely to be directly comparable.  It
might be fun to compare Microsoft BASICs on each machine.

My suspicion is that for programs that work on small data sets, a
hand-optimized 6809 assembly language program could compare well against
the 8088 or 8086.  There might be better-optimizing compilers available
for the 808[6|8], and it can (sort of) directly address more than 64K
(though the segmented address space might slow things down a little), so
the Intel chip might edge the 6809 out when dealing with larger amounts
of data, or compiler-generated code.  I don't know for sure though.  The
6309 would probably give it more of a run for its money, if fully
utilized.  The 8088 can't do block transfers as in the TFM instruction. 
On the other hand, the IBM PC has a DMA controller.

Certainly if you do a price/performance comparison between the CoCo and
the IBM PC at their 1980s prices, the CoCo would be hard to beat.

> Diego
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