From:	atlas_wang AT yahoo DOT com (Wang Yong)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Hardware Interrupt Latency in Protected Mode?
Date:	14 Jul 2003 12:32:17 -0700
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References:	<78a4a70a DOT 0307080821 DOT bdb7edb AT posting DOT google DOT com> <7263-Sun13Jul2003220045+0300-eliz AT elta DOT co DOT il>
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Thanks for your reply. 

DOS in my computer is configurated as simple as possible. In fact, I
tried it in both FreeDOS and MSDOS. In config.sys, only
    files=20
    buffer=20
In autoexec.bat, only path is set. 
When running my test program, *ALL* maskable interrupts are disabled
except IRQ7. And in my code, no chance to change to real-mode. Memory
is normal NON-ECC memory. However, since the computer is an industrial
PC, a lot of modules are integrated on the motherboard, such as
network controller (Intel 82559). With the help of both of you, I can
make sure that it's the hardware problem. But it's really difficult to
figure it out that which part causes the problem.

I will do the same experiment on some old computers. And if you are
interested, I'll post the result.

Thanks again. 


Sincerely,
Wang Yong

"Eli Zaretskii" <eliz AT elta DOT co DOT il> wrote in message news:<7263-Sun13Jul2003220045+0300-eliz AT elta DOT co DOT il>...
> > From: atlas_wang AT yahoo DOT com (Wang Yong)
> > Newsgroups: comp.os.msdos.djgpp
> > Date: 8 Jul 2003 09:21:45 -0700
> > 
> > Normally, the latency is
> > less than 6 microseconds, which is really reasonable. However,
> > sometimes (in 1 or 2 hours), a very large latency, 30 to 60
> > microseconds, can be observed.
> 
> Sounds like some code in the BIOS.  BIOS is known to disable
> interrupts for prolonged periods of time; I've seen similar problems
> on occasion.  Disk I/O is the usual culprit.
> 
> Can you post the details of your system configuration (CONFIG.SYS,
> AUTOEXEC.BAT, etc.)?
> 
> > And what steps should be strictly foloowed to
> > restrain the latency in an acceptable range, such as < 10
> > microseconds?
> 
> Unfortunately, I didn't find any work-around for this, except to
> prevent the relevant BIOS code from running (which is not always
> possible, alas).

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