pl@tut.fi (Pertti Lehtinen) (07/20/88)
Someone asked about function of MC68000 DBcc instruction.
I wasn't surprised, because intruction is quite
hard to understand.
That came clear to me when I read MC68020 Benchmark
Report released by Motorola. There was text about various
bencmarks and one of them was loop-test, which is in C:
main()
{
long i:
for(i=0;i<1000000;i++)
;
}
About this benchmark there was text:
"This benchmark tests both the compiler efficiency and the
processor speed. The Alpha Micro MC68020-based machine
( the AM-2075) wiyh the compiler optimizer enabled was
able to execute the routine in 0.009 seconds! That is,
90,000 microseconds for 1,000,000 iterations, or an
effective rate of 11.1 Million iterations/second!
The code generated by their compiler was:
main move.l #1000000-1,d0
loop DBRA D0,loop
"
So if they don't know how it works,
how could anyone else?
--
pl@tut.fi ! All opinions expressed above
Pertti Lehtinen ! are preliminary and in subject
N 61 26' E 23 50' ! to change without any further notice.