RE: [GD-Windows] More timer fun!

[Jon W. <hp...@mi...>]

timGetTime() / GetTickCount() only return 32 bit values, AFAIK.

There are some problems with keeping time on PC hardware. timeGetTime() 
will lag behind wallclock time when there is lots of bus traffic (== 
graphics-heavy application running). QueryPerformanceCounter() will 
somtimes jump ahead by 1.3 or 4.1 seconds when there is lots of bus 
traffic, in a quantum leap. RDTSC ticks once per cycle, but mobile 
CPUs will adjust their CPU frequency quite often, so you can't get a 
good bead on that, either.

Also, QPC and TGT/GTC each take a bus transaction to execute, and thus 
run in 1-2 microseconds, which is an eternity if you need to call them 
more than once or twice per frame rendered.

I ended up with an unholy concoction of all three methods, which ends 
up getting good overall relation to wallclock time, cheap calls, but 
some local mis-match where my clock will lag behind wall-clock "locally" 
but get adjusted "globally" when the CPU goes into powersave mode.

Yuck.

Cheers,

			/ h+


> -----Original Message-----
> From: gam...@li...
> [mailto:gam...@li...]On Behalf Of
> brian hook
> Sent: Thursday, August 29, 2002 9:40 PM
> To: gam...@li...
> Subject: [GD-Windows] More timer fun!
> 
> 
> Well, in the process of trying to figure out why on a very few systems 
> (maybe less than 1%) my timing code was messed up, I stumbled across 
> this tid bit at the Pest Patrol Web site:
> 
> "A Range Check Error can occur on DELL computers running Windows ME 
> with software using the Windows function GetTickCount. In such systems, 
> this function is not returning the elapsed time since system power on, 
> and the value returned can be enormous, causing a range check error. 
> Dell's Range Check Error affects timeGetTime as well as GetTickCount. A 
> third timing function, therefore, has been used in PestPatrol, 
> PestPatrolCL, and PPUpdater."
> 
> Well, sure enough, the two users I know that were having this problem 
> have Dell Dimension L's with Windows ME.  I'm not sure what the 
> specifics of this problem are (I'm using 64-bit ints already), but I do 
> some more range checking now and hopefully this problem goes away.
> 
> -Hook
> 
> 
> 
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