> 1) What is a BogoMIP?
It's the value determined to calibrate a delay() loop.
More specifically:
On the iX86 architecture, the following loop is executed for short delays:
1: decl %eax
jns 1b
ret
whichs equivalents the instruction "while (eax) eax--;" in C (eax is a
32bit register which is set to a calculated value before the loop is
called).
The BogoMIPS value indicates the number of Megaloops executed per second.
On some machines (6x86 for example), the CPU takes exactly one cycle to
execute the loop, so you find a value matching the frequency. The pentium
takes 2.5 cycles. I don't know about the MMX.
> After numerous kernel recompilings I have noticed that this number changes
> constantly and in many times will be much more or much less than the
> previous kernel. (I believe I have seen this as high as 720.xx)
On Pentium machines, the alignment of the branch target (i.e.the 1:) has
some influence on the execution speed. That's why the loop is no longer
inlined in recent kernels, so it's possible to have the loop always
execute with the same speed (and to control alignment?). This change was
done in 2.0.31. As the assymbly code in arch/i386/lib/delay.S does not
specifiy any alignment, there is still a chance to find different values
after recompiling the kernel, I believe.
> 3) /proc/cpuinfo shows twp cpu's listed but the system does not behave as if
> it was scheduling
> both cpu's (when compiling software mainly). Before, under 4.2 I compiled
> the same code on
> the same machine _much_ faster. How can I verify both cpu's are being
> scheduled without
> relying on some text file created at boot up?
Be sure, that your system load is low. Compile some software package
twice:
1) make clean; time make
2) make clean; time make -j2
The second one should be much faster than the first one (in theory: double
as fast) if both CPUs are used.
> btw: This is a Tyan board with 2 matched Intel 200mmx chips. Any known
> problems with these boards?
No idea.
Kurt Garloff, Dortmund
<K.Garloff@ping.de>
PGP key on http://www.student.physik.uni-dortmund.de/homepages/garloff