Re: cpu arch performance
Daniel Reuter <reuter@Uni-Hohenheim.DE> writes:
> On Tue, 23 May 2000, Lee Elliott wrote:
> > Just something I noticed after setting up an x86 system after running
> > Debian on m68k.
> >
> > The m68k system was an Amiga with an m68060/50MHz which gave a BogoMIP
> > rating of 99.something. The x86 system is a dual PIII 650MHz system and
> > it rates as 2600 BogoMIPs. This would seem to imply that on a per MHz
> > basis, the m68060 is the equivalent of two PIIIs.
>
> This is right.
[...]
> holds true for 386 and 486). This is why a m68k processor is on a per MHz
> basis really twice as fast as a x86 processor.
Not really.
It is true that the later 68ks drive at least their integer units at
twice the external clock rate (don't know about the FPU). And, in
contrast to Intel's 486DX/2 and later processors, it is the external
clock rate that Motorola tacks onto the processor name.
*But* the BogoMips are just that: bogus (they have that name for a
reason). You can infer *nothing* from them (other than how to
parameterize a delay loop in the kernel). For example, a Pentium gets
2 BogoMips per MHz, and a Pentium Pro get 1 BogoMip per MHz, but in
most situations a Pentium Pro gets a least as much done per cycle as a
Pentium (this is a slight understatement). Read the Bogomips HOWTO.
If you want a speed comparison, time some software that interests you.
Compile a kernel. Do some large FFTs. Compare these results to the
clock rate if you like. Compare to hardware cost if you want more
meaningful numbers.
HTH,
Matthias
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