I wish I could run my BIOS in a debugger.

March 12, 2008 7:24 PM

Help me guess which part of my homebrew PC is causing my POST video failure.

I built this box six months ago. Its stability has been flawless. Now, suddenly, my POST keeps doing a <long>beep</long> <short>beep beep</short> which for my BIOS is a video failure. It then boots sans video. If I unplug the power and fool around for 15 minutes or so (that's as precise as I can be after a couple evenings of despair) it will boot with video again.

This is my parts list; here it is on Newegg with moar linkies if you have a login there. The proc is a 45W Athlon X2 and I dual-boot XP and Ubuntu. There are a few vaguely related prior questions but I couldn't find any love for my particular crisis. I'm having the same POST error as phrontist here, but he had a notebook.

Is it the:

• Video card? It's a fanless NVIDIA 8500, which is allegedly somewhat fail-y due to the passive cooling. However, the system has never had any instability or lockups in six months and when it boots again after fiddling it's rock solid.


• Motherboard? The fact that the system is stable once it boots makes me wonder if maybe the BIOS is somehow flaky.


• PSU? It only boots now after the system has been unplugged for a while...

I talk big but I am fairly ignorant about hardware and haven't built a system since like 2001. All of the above is (I think) returnable but the software developer in me wants to know what is going on. What do you think is wrong? What would you do in my shoes?

posted by mindsound to computers & internet (12 comments total)

on my system, it was a bad video card with similar symptoms. If you have a spare (or can borrow one), I'd start there, especially since that's what the POST is telling you.
posted by jenkinsEar at 7:37 PM on March 12

Does the video card have an additional power input that maybe you forgot to connect? Does the motherboard have multiple PCIe slots that you can try?

Yes, I'd consider the PSU a candidate for problems, especially if it's a cheap one. However, the video card seems more likely at this point.
posted by knave at 7:41 PM on March 12

For problems like you're describing - intermittent video failures - I find the most likely candidate is the physical connection between the video card and motherboard. I've had systems where screwing the video card down all the way would cause the opposite end to lift out just enough to cause problems. I know the hinge design on a lot of modern video cards would seem to stop that, but they often don't.

In general I've found motherboards, ram, CPUs and video cards to have become remarkably reliable in the last decade or so. Hard drives and power supplies seem to be less reliable in recent years, sadly.
posted by mragreeable at 8:05 PM on March 12

jenkinsEar: I just managed to find a buddy with a spare, so I can give that a shot tomorrow...

mragreeable: Huh. I did try reseating this card several times, to no avail. Unfortunately my case is screwless (i.e. has little plastic locking tabbies instead of slot screws) so I can't adjust the card's seating much.
posted by mindsound at 8:13 PM on March 12

Every time I have video-card problems, blank screen on boot, it's always been the RAM. Take one stick out (then the other if no improvement), or swap them around/put them in the alternate bank and see if that clears it up

If it does, run memtest on the RAM and see which one is faulty (assuming you have more than one).

Hope it works!
posted by Static Vagabond at 8:26 PM on March 12

I looked up the BIOS beep code at BIOSTAR's website. On page 41 of the PDF, which you can find here, it says, "One long beep followed by two short beeps" means "video card not found or video card memory bad."

So, I think you're on the right track. I agree with jenkinsEar.
posted by tcv at 8:43 PM on March 12

Reseat the video card.
posted by zippy at 10:21 PM on March 12

Maybe it's overheating? You've said it was stable before, but if your computer has been accumulating dust or if a fan has stopped working, it could make it much hotter.
posted by alexei at 11:31 PM on March 12

Don't just reseat it. Take it out, and have a good look at the edge connector (both sides) under a strong light. I'm betting you will find at least one old fingerprint on there that's finally oxidized itself into a lovely insulating lacquer.

Even if it only looks a little bit dull, clean it up before you plug it back in. To do this:

0. At no time during the following procedures, or at any other time, should you touch any edge connector with your bare fingers.

1. Discharge any static electricity you may have built up by touching the computer's chassis.

2. Rub firmly over one side of the card's edge connector with a white pencil eraser. Don't use an ink eraser; they're too abrasive. The action you should use is the same as you'd use to rub out a pencil mark on paper.

3. Blow off all the tiny rubber crumbs. Don't blow them onto the mobo.

4. Repeat step 1, turn the card over, and repeat steps 2 and 3.

5. Blow extremely hard into the card's empty slot before reinstalling the card. If you have canned compressed air, or a shop air compressor with a hand nozzle, use that; otherwise just a good strong puff will do. Don't spit.

This trick has been successfully resurrecting flaky cards for me since my first Apple ][+.
posted by flabdablet at 11:42 PM on March 12

Afterthought: after the first go at step 2, compare the side you've just cleaned with the side you haven't. It will usually be noticeably cleaner and shinier.
posted by flabdablet at 11:44 PM on March 12

All good suggestions. I guess I don't understand what you mean by "booting without video." I have built a lot of systems, and it is not unusual for me to end up buying two of everything trying to track down a problem (by swapping components). I've had the most bizarre problems turn out to be a faulty optical drive. Your symptoms do remind me a bit of when the first Athlon 64 system I had built for my son got too much dust in its CPU fan and overheated (it's really dumb how long it took me to realize that was the problem).
posted by thomas144 at 8:05 AM on March 13

flabdablet: didn't work. :(

thomas144: it finishes booting with the video card completely dormant. I know it's booted because I can ssh in and poke around etc.

I'm scrounging for spares... let the swapping begin! Thanks all.
posted by mindsound at 6:30 PM on March 13