Re: [GD-Windows] More timer fun!

[Pierre T. <p.t...@wa...>]

Somebody should write a definitive Gem about this (say in GPG 4 ?). Or maybe
someone already has and I don't know about it ? Is there a place explaining
the issues and, hopefully, giving canonical source code to solve them once
and for all ?

Pierre

----- Original Message -----
From: Jon Watte <hp...@mi...>
To: <bri...@py...>; <gam...@li...>
Sent: Friday, August 30, 2002 6:51 AM
Subject: RE: [GD-Windows] More timer fun!


>
> 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+