ASM Community

Hi, there,

I am trying to create a very accurate timer (10-15us range), with a resolution of 1us.
I noticed that even if I temporarily change the process's priority class to REAL_TIME_PRIORITY_CLASS and boost the thread priority to maximum there still are longer intervals from time to time.

Is there a way of disabling the interrupts completely? Any other suggestions?
Also, QueryPerformanceCounter does not work under Windows XP Home edition. Does anyone know why?

Thanks,

Hi, awerX,

These don't seem to work in the microsecond range.
Any other suggestions?

Thanks,

If you really want to use Windows for such ultra-sensitive things, look here:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/WinUI/WindowsUserInterface/Windowing/Timers.asp

Aww, I saw somewhere on a way to disable interrupts under win98, but I can't find
Edit:
http://sourcevault.scali.eu.org/cgi-bin/Syntax/Syntax.cgi?ring0.c



I guess this would work:
(I don't know whether you used RDTSC) . Try not to start the code right away, first have a Sleep(0) and SwitchToThread()

include Ring0OnOff.inc ; make it yourself



invoke GetCurrentProcess

invoke SetPriorityClass,eax,REALTIME_PRIORITY_CLASS

invoke GetCurrentThread

invoke SetThreadPriority,eax, THREAD_PRIORITY_TIME_CRITICAL

invoke Sleep,0

invoke SwitchToThread

invoke RING0ON

_again:

RDTSC

push eax





;------------------------\



;.. now do your code

; here



;------------------------/



@@:

RDTSC

pop ecx

sub eax,ecx

cmp eax,7000 ; roughly 15microseconds, calculate for your cpu

ja _again

push ecx

jmp @B



invoke RING0OFF