Intermittent PrePOST Hangs
June 16, 2006 8:57 AM   Subscribe

How can I trouble a system that intermittently hangs before the POST?

It usually boots fine but every week or so the system starts up and starts displaying the Bios info and then hangs with just after writing Memo. (The start of the line for the Memory Test). Would this mean the memory test is failing right away? What other things can I look into?
posted by srboisvert to Computers & Internet (10 answers total)
I would get one of those POST status code readers (they go into a PCI slot) and pop it in and see what the code is when it hangs. the fact that it's not even getting to the memory test makes me want to think you've got something borked up on the motherboard, or your memory has problems right at the start of it.
posted by mrg at 9:03 AM on June 16, 2006

Is the squeaker hooked up? You can occasionally hear a beep code when the machine croaks during POST.

(By the way, the part where it's writing "Memo..." is about midway through the POST, not before it. The memory test isn't the first self-test performed.)
posted by majick at 9:33 AM on June 16, 2006

You could also try to test components in isolation, though this can be difficult if you have no other hardware kicking around.
posted by utsutsu at 9:40 AM on June 16, 2006

As majick mentioned, one way BIOS reports errors is by producing beep codes. For example, if you hear a long beep followed by two short ones, BIOS is telling you there is a problem with the video adaptor.

Another way BIOSes report errors is by writing a one-byte error code to I/O Port 80 (some use Port 84). If you get a debug card that displays these codes, you might be able to figure out something. I don't think these codes are completely standard, though, so you'll need to find a chart specific to your BIOS.

Regarding your boot up symptoms, I don't think it's failing during the memory test. I base this on the fact that it choked in the middle of displaying a message. BIOS isn't going to be multi-tasking a memory test with displaying a message.
posted by iconjack at 10:16 AM on June 16, 2006

If you have more than one stick of memory installed, pull half of it and see if the problem goes away. If it doesn't, put the pulled memory back in place of the installed memory and try again. If you have more than two sticks of memory, you may have to try several combinations to find the bad memory. Or it may not be the memory at all.

If you're handy and your computer has the diagnostic port, you could build a tester.
posted by donpardo at 10:24 AM on June 16, 2006

iconjack's suggestion is probably better than mine.
posted by donpardo at 10:25 AM on June 16, 2006

I'd got through this procedure:
1) Disconnect all drives except for the primary master.
2) Take out all but one stick of RAM.

-- Try booting up, if it fails again, try a different stick of RAM. Once it actually boots, keep adding back devices one at a time until it breaks.. that would be the bad part.
posted by triolus at 12:26 PM on June 16, 2006

1. Memory test
if you get tons of error messages, you've got a bad stick. Pull one stick at a time, and find out which one is giving you errors. Also, if you find a bad stick and a good stick, put the good stick in the slot where the bad one was, to make sure it's not the slot.

2. It could be your powersupply not giving enough power to spin up hard drives, but that doesn't usually give this sort of behavior.
posted by defcom1 at 1:32 PM on June 16, 2006

Also, make sure you have the latest BIOS for your motherboard. First cuts at BIOSes for new motherboards are often pretty buggy. A bug consistent with your symptoms would be, for example, a low-quality chip that produces an interrupt before the interrupt vector table is fully initialized.

When it fails, does it always display exactly MEMO, or does the number of letters vary?
posted by iconjack at 9:53 PM on June 16, 2006

Response by poster: It's always Memo.
posted by srboisvert at 2:45 AM on June 17, 2006

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