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http://www.osdev.org/mediawiki/index.ph ... ample_Code

I recently setup my exception handlers and I have setup the PIT IRQ.

Now, I was wondering how could I accurately calculate how many fractions of an mS and how many mS should I add to the system timer each time the IRQ fires?

I tried looking at the code example, but for some reason I don't really get why 2^32 and 256 is used everywhere (I do understand why the example uses 3579545/3 though). Maybe coffee level dropped too low or I didn't sleep enough, but I'm not getting it at the moment.

Anyone want to look at it and perhaps post their thoughts?

you dont time with PIT, you do the time the realtime clock. It is designed for it and has a 1ms accuracy. or the local apic for that matter.

But in many topics I read here, the PIT IRQ is used to measure time. And by reading the code example, I assume the code example uses it for the system timer too?

Btw, any info on how to access the RTC?

Hi,

bughunter wrote:I tried looking at the code example, but for some reason I don't really get why 2^32 and 256 is used everywhere (I do understand why the example uses 3579545/3 though). Maybe coffee level dropped too low or I didn't sleep enough, but I'm not getting it at the moment.

Anyone want to look at it and perhaps post their thoughts?

I took a look - it was unnecessarily complicated and had some bugs. I fixed the bugs and simplified it a little...


Cheers,

Brendan

Thanks . I will have a look at it when I have some more time.