On Friday, 98/12/25, mark lewis wrote to David Noon about "Guess who's
back... ;)" as follows:

Hi Mark,

ml> IT>>      cli
ml> IT>>      x:
ml> IT>>      jmp x
ml> IT>>
ml> IT>>     Execute this in a DOS window.
ml> IT>>
ml> IT>>     Hope you closed all the applications first... ;)
ml> 
ml>  DN> It just means you have a duff machine. Those of us who have
ml>  DN> EISA or MCA motherboards have the watchdog timer in the bus
ml>  DN> control chipset to deal with excessively long disabling of
ml>  DN> interrupts. The VDM will trap with an NMI and order will be
ml>  DN> restored _on_a_decent_machine.
ml> 
ml> what about continous disabling of interrupts?

Yes, that's exactly what the watchdog timer in the EBC chipset is for:
generating a NMI when the bus has been locked for too long (something like
100 milliseconds). It's a hardware feature of the EISA and MCA bus
architectures. It is useful on 80386 and early 80486 systems.

Later CPU's (clock-multiplied 80486, Pentium, PPro and P-II) support
virtualized interrupt handling, inluding masking.

ml> i don't 
ml> believe that IT posted the above snippet as it should have 
ml> been... i just posted it in another message as i recall 
ml> it...

I saw it.

It doesn't matter whether the label is before or after the CLI instruction.
It will still lock up an ISA or ISA/VLB or early ISA/PCI system. The ISA bus
is crap.

Regards

Dave


 * KWQ/2 1.2i * Macintosh: Just like Nintendo but fewer games available.

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