Newsgroups: comp.os.msdos.djgpp
From: manni DOT heumann AT gmx DOT de (Manni Heumann)
Subject: Re: How to get bios timer tick count?
References: <8cg55n$1kl$1 AT mailint03 DOT im DOT hou DOT compaq DOT com> <38EB9E19 DOT FDEEB2C4 AT corel DOT com> <esRG4.639$x62 DOT 2898 AT typhoon DOT southeast DOT rr DOT com>
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Date: Thu, 06 Apr 2000 07:40:16 GMT
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

"pwillard" <pwillard AT mindspring DOT com> wrote:
>
>Actually, I'm not too afraid of straight C code, but accessing BIOS
>information as in  the FAQ
>made me very cautious. I'm not sure how to access the rom bios area to
>perform what the old pascal
>code was doing.
>
>Here is the snippet of Pascal:
>
>TICK :=  LONGINT(PTR($40, $6C)^);         {GET ROM BIOS TIMER TICK COUNT}
>
> Should I be more creative when accessing the system as done in the example?
>I mean, what's the magic?
>
>I know that the 8253/8254 uses a 4 byte area located at 0040:006C
>(segment:offset notation) for
>incrementing a counter and that's exactly what the code above does.
>
>I want to snap shot the counter, and compare it's value to a snap shot later
>for speed calibration.  I
>just don't understand yet how to tell DJGPP to do this without whacking the
>system into oblivion.
>
>Pete
>(Who's afraid to touch memory directly after reading the FAQ. )

It's not that bad. Of course it's different with a 16 bit compiler, pascal, c 
or whatever. I suggest you read the far pointer intro at
http://www.delorie.com/djgpp/doc/ug/dpmi/farptr-intro.html


--

Manni