MUSIC-DSP digest 321
eli at gs160.sp.cs.cmu.edu
Thu Sep 10 11:23:34 EDT 1998
Martin Fay wrote:
> That isn't strictly true...and idling 95 box with no win16 apps
> running never seems to show jitter this bad.
Dunno about "never". I saw 396 ms on an idle freshly-booted 95 box
with the usual tricks (no network, no CD-ROM polling, that type of
thing). And I bet you'll see higher if you want to wait long enough.
(Should have mentioned, though, that a W95 DSound app can quite well
do 20-ms latency by using a 16-bit timer.)
> This relates back to the
> jitter being caused by the mutex used to control access to 16bit OS
> services. A simple demonstration of this is moving the window of a
> win16 app around...in fact that can block timer callbacks
I think the UI-update mutex can cause similar problems even in the
absence of 16-bit apps. (Those slide-out menus in W98 will hammer the
timer for 200 ms, I can tell you.) Last I heard, nobody knows _what_
all the jitter in NT4 is caused by.
Eli Brandt | eli+ at cs.cmu.edu | http://www.cs.cmu.edu/~eli/
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