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A500 works but then won't reboot after taking its second CPU out

 
Richard Lloyd_8
Occasional Contributor

A500 works but then won't reboot after taking its second CPU out

The A500 we have is well beyond its warranty date and we wanted to take its second CPU out (don't ask the reason why, we just do...and it's not to sell on eBay before you ask :-) ). We've followed the instructions available on hp.com (well, for the rp24xx series - same class of hardware), including cleaning the contact area carefully and including any CPU "terminators" (which just look like big screws to me, but whatever).

When we power the A500 up with just one CPU instead of two, it comes up perfectly with no faults at all. We let it run for a few hours and then try a reboot, at which point, the power light goes from flashing to steady at the very start of the reboot process and then it locks solid (nothing at all ever appears at the console).

One of our guys thinks it could be voltage regulators, but he isn't sure. Does anyone have any ideas what could be wrong?
3 REPLIES 3
Stefan Stechemesser
Honored Contributor

Re: A500 works but then won't reboot after taking its second CPU out

Hi,

I don't think that this is really a hardware problem, because the machine is running fine for hours and you only have a system hang during a reboot.
If it is a hardware problem, the fault LED should lit and the GSP should log some errors. OK, there are a few corner cases were we do not get GSP entries even if we have hardware problems, but in this case, I would recomend to make TOC ("tc" on the GSP prompt) to get a memory dump that should be analyzed by someone with enough kernel knowledge (yes, the HP support could do it).
Take a look on the /etc/rc.log.old file to find out at what point the reboot produced a hang.
If there are errors in the GSP error log ("sl" at the GSP> prompt) please post it, maybe it helps finding the cause of the problem.

Best regards

Stefan
rick jones
Honored Contributor

Re: A500 works but then won't reboot after taking its second CPU out

If you want to rule-out problems with terminators and the like, you could return the second CPU to the system, make sure everything runs OK, and then reboot and disable the CPU from firmware rather than removing it entirely.
there is no rest for the wicked yet the virtuous have no pillows
doug hosking
Esteemed Contributor

Re: A500 works but then won't reboot after taking its second CPU out

Rick's idea of disabling the CPU from firmware is good if you want to permanently turn it off without opening the box.

Alternatively you could disable the second processor for a single boot by:

ISL> hpux -P1 /stand/vmunix

(Since you don't want us to know why you're taking it out, I can't tell if you want to test with only one processor or if you need to use the removed processor somewhere else.)