John Rumm wrote:

The Natural Philosopher wrote:

No. Happens randomly when nothing else is going on. Rebbot (hard)
always fixes it, so cannot be stuick key. Ctrl Alt Del doesn';t work
at all, neither does any key - e.g. NuimLock - cause any keyboard
light to change state. The amount of hardware and software involved in
e.g. getting a keybaord light to change state is very small - probably
tehkeyboard, teh UART and a timney code fragment invoked under interrupt.

Its definitely UART, processor or memory.


Or a corrupted mouse or keyboard driver - have you tried expanding these
again from your windowss CD?



not a bad idea.


Also check if your BIOS has a fast A20 gate option. If it does, and its
turned off, then turn it on and try again! (Why is a long and complex
story!)


mmm.


Have you also tried a differnet keyboard?



nope. I don;t think that is th eproblem tho...


Its possible i have a corrupted disk but I doubnt it. My giess is that
teh interrup part of the chipset has gone off the edge of its timing
somehow, and/or the UART is faling to respond correctly,


If it's hardware you would probably find a motherboard change would fix it.

The processor should be pretty well isolated from anything nasty
happening to the PS/2 mouse port. So unless you have roasted it good and
proper it ought to be OK.


I roasted it good and proper - that fan has been stick all summer I reckon.

Heatsink was about 70C with the fan off.


Further data.


The random mouse movements have now almost completely gone, with
restarting of the fan. The current case is that the processor seems to
get 'stuck' - presumably in an ISR - for periods of between a few
milliseconds to permanently. Sometimes the keyboard works, and
Ctrl-Alt=-Del will allow a soft reboot, and sometimes its truly stuck.

The fact that its oinconsistent and seems temperature dependent leads me
to a hardware explantion.

Is the keyboard UART integrated on the pentium? Or is it a separate chip?.

I can change motherboard, processor or m,emory, but don';t want to
change all three - expensiove









PS what makes you think its getting stuck in an interrupt service
routine?
Thats not easy to diagnose.




20 years as a hardware engineer and ten as a real time software engineer?


Its very easy to diagnose. Only an ISR turns off enough interrupts to
e.g. make the keyboard caps lock and num lock toggles stop working.


A "CLI" would do it as well!


Yes, but that would simply freeze everything.

Note also that the keyboard is on IR1 on
the master PIC so it usually has priority over most interrupts except
the system timer (assuming the 82c59 equivilent in the chipset is still
set to "special fully nested" mode, as it is in the BIOS initialisation!


Its windows 98 so its fairly primitive.


probably a rash assumption these days since the whole lot is virtualised
by protected mode code in the VXDs that deal with mouse and keyboard
anyway)



In W98?


I need new hardware. No sure if a Pentium III is the way to go, or
simply swap the motherboard. Is only 18 months old too.


Socket 370 I hope ;-)



Dunno. Lost of pins and a square socket.