Author: Andrew Dados
Date: 00:06:48 08/08/00
Go up one level in this thread
On August 08, 2000 at 02:34:54, James Robertson wrote:
>On August 08, 2000 at 01:54:48, Andrew Dados wrote:
>
>>On August 08, 2000 at 00:25:06, James Robertson wrote:
>>
>>>I am trying to measure clock cycles for certain functions in my program. Could
>>>sombodey please explain how to do this? Totally simple methods are preferred. :)
>>>
>>>Thanks!
>>>James
>>
>>All modern CPUs starting with Pentium and K2 have TSC 64 bit counter which gets
>>incremented by 1 for each CPU clock.
>>Under protected mode reading from this counter is by default disabled, but for
>>some reason any task can enable instruction for reading TSC.
>>
>>(I'll be quoting asm code I wrote before some instructions were supplied by C
>>inline asm, so in some cases I had to define instructions myself)
>>
>>enabling TSC:
>>
>>asm
>
>Thanks, this looks cool. Unfortunately, I don't know how to interpret the db
>instructions... how can I use them in VC++?
>
>James
>
>
>>db $0f, $20, $c0 {mov eax,cr4}
>>or eax,32 {Enable TSC}
>>db $0f, $22, $e0 {mov cr4,eax}
>>end;
>>
>>reading tsc:
>>
>>asm
>>db $0f, $31 {RDTSC : 64bit unsigned tick count goes to eax:edx}
>>end;
>>
>>So writing mini-profiler got really easy with RDTSC.
>>One remark: TSC is a global counter, not task-related.
>>
>>-Andrew-
db srands for 'define byte' and is standard asm directive...
Look up eg crafty source for how to write procedures in assembler and readable
by C compilers.
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