im trying to benchmark programs with RDTSC.
well this opcode returns a 64 bit value in EDX:EAX

any ideas how i could subtract 64 bit values, not the normal 32 bit that registers use.. i just never used fpu but im sure it can be done with that.
Posted on 2004-11-15 01:53:50 by pwn
assuming the other 64-bit number in ecx:ebx
sub eax,ebx

sbb edx,ecx
Posted on 2004-11-15 02:37:33 by optimus
The return value may be a 64-bit one but you can generally forget about the higher 32 bits unless you suspect that the final result would exceed 4,294,967,295 units. If below that limit, only retain the value returned in EAX and treat it as an unsigned 32-bit value.

Posted on 2004-11-15 21:18:45 by Raymond