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I specifically asked for Windows XP because I'm not too confident in Vista.

GodzFire wrote:

I specifically asked for Windows XP because I'm not too confident in Vista.

I love this guy.

WoWDude wrote: The origin of this "performance boost" is quite simple. Almost all of the applications are using system timers in some of the ways. This is a natural way of telling the system "Hey! I wanna draw this thing in 5 milliseconds. Now I'm going to sleep, wake me up in 5ms!". Windows has a thing called multimedia timers. These are the only timers with a high precision and predictability (up to 1ms resolution). By default these timers run with a precision like 10ms. So if the application want to wait for something using a 3ms interval it will actually have to wait for 3-10 seconds. Windows Media Player is using documented Windows functions (timeBeginRange, timeEndRange) which allow the system to boost the timers precision up to 1ms. You may ask why Microsoft didn't set this by default for you, well... Increasing timers resolution will cause your CPU to handle more interrupts and it will cause greatly increased power consumption (especially in sleep modes). Usually most of the applications don't really need such precision. So it is recommended for the software developers to only use this function when they're have a lot of heavy multimedia processing in their code.

WoWDudeAgain wrote:Just try to create a simple application making timeBeginPeriod call and see the results. Don't forget that in real world of Windows multitasking you really need to take the kernel scheduler into account. Usually you can't do internal high-resolution time management all of the time just eating all of CPU cycles.

World of Warcraft's main thread (as far as i can see) spends most of the time doing system sleep() calls and calling WinMM time management functions. THAT'S why increasing the interrupt rate of the system timers leads us to the performance boost.

#include <stdio.h>
#include <windows.h>

int main(void)
{
timeBeginPeriod(1);
printf("Press any key to restore normal timer frequency.\n");
getchar();
timeEndPeriod(1);
return 0;
}