Mail Archives: djgpp/2002/01/29/22:45:29
> Tried the way you suggested - but it doesn't seem to work if I try
> invoking the hardware interrupt through a software (INT XX) call. I
> hooked INT0D (IRQ5) from protected mode. But on reaching the shell, The
> interrupt vector of Int 0d was pointing to the initial Real mode value
> in ROM.
Right, it reprograms the pic. Sorry, forgott to warn you about that.
> I then tried calling Int8D (where the master PIC vector seemed
> to be redirected to), but still my interrupt handler didn't seem to get
> called. Does the code check if the interrupt is a genuine hardware IRQ
> and skip calling the handler if it isn't ?
It shouldn't. You can look at the sources.
> Anyways, managed to do the tests by hooking IRQ8 (timer interrupt) and
> writing a small Real mode routine which hangs on in Real mode till a
> fixed number of Timer ticks ahve passed. On return from the Real mode
> call, the delays were averaged. The results were as follows (for 100
> samples, values are rounded to 50 clocks - CPU is P3 - 933 MHz)
>
> With CWSDPMI : Maximum 6500 clocks, minimum 3200, Average 3500 clocks
>
> With PMODE/DJ : Maximum 3100 clocks, minimum 1200, Average 1250 clocks
Very interesting. I'm surprised there is that much variability (nested
interrupts?) The averages are pretty close to what I had tested or
had reported to me in the past (around 2-4K for CWSD, 1-2K for PMDJ),
I had expected a little over 2X speed difference. The Min/average
show the maximums are fairly rare - in pmodes case about 2/100 or less?
> I assume the reason for the maximum numbers being much larger than the
> average could be because of instruction cache misses ??
A few cache misses wouldn't add up that badly. It's something more
terrible...
> Hope this information is useful to someone.
Very much so. Hard facts make good references. I don't suppose you
could re-run the test for CWSDPR0? :-) For completeness/documentation.
> The PMODE/DJ numbers seem to be more or less acceptable for my
> application, and so not investigating the "Unreal" mode approach
> immediately. May be later when I have some spare time..
>
> If anyone is interested in the source code of the test program used to
> do the above tests, pl. let me know, I'll be glad to post it.
Plese send, I'd like for my test suite.
> Thanks for all the help.
Certainly. Thanks for the test results.
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