Author: James Robertson
Date: 10:21:45 08/09/00
Go up one level in this thread
On August 08, 2000 at 04:09:41, Andrew Dados wrote:
>On August 08, 2000 at 03:31:21, James Robertson wrote:
>
>>On August 08, 2000 at 03:06:48, Andrew Dados wrote:
>>
>>>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.
>>
>>I've written a large amount of assembler.
>>The compiler chokes on the arguments, not the db statement itself. :(
>>
>>James
>
>Hmm.. instead of $0f try 0x0f etc... :)
>(I copied/pasted that code from my delphi proggy, forgot about hex convention)
>-Andrew-
Ok, cool, thanks. :)
James
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