Asus P5B does not POST, but it used to...


Jul 1, 2005
Hello everyone, was looking through the forum for someone with the same problem as I have, but couldn't find any.

Here's my system:
Asus P5B
2 x Crucial DDR2 BallistiX PC6400 1024MB CL4 (2.1v)
Intel Core 2 Duo E4300
Hiper Type-R 530W Black
Samsung SpinPoint T166 500GB SATA2
XFX GeForce 8800GTS 500M 320MB GDDR3

System was built May 11th.

This system worked fine right from the very beginning. I decided to OC a bit, so I increased the FSB to 333MHz, leaving me with approx. 3GHz cpu frequency. Using only the boxed fan and a casing with very good air flow the core temperatures stayed at about 50 degrees celsius at full load (30-35 idle). Please note that first I only tried an FSB at 220MHz, but when that failed I, after some troubleshooting, managed to get it to boot when I increased the RAM voltage (default was too low) to 2.1 or 2.25 (can't remember which), and after this there were no problems increasing the FSB further.

So, all was fine and well until last night when I was going to play a game (spiderman 3 if that is of any interest to you ;)). I started it, intro videos showed and then *BOOM*, a quick flash showing a BSOD and then comp rebooted. However, I got no video at all. Thinking it was an OC problem I shut off the PSU completely (which had worked fine at earlier OC errors) and started computer again, but I still got no boot, no error beeps and no other indications what could be causing this. I tried to reboot the computer like this several times, but no improvement what so ever.

So here I am, computer doesn't boot and doesn't indicate any error. I have tried the following so far:
* Remove battery and flipped jumper to clear CMOS, kept it like that for about 12h although 5-10s should be enough according to MB manual.
* Reseat video card, RAMs and processor (looked for bent pins at the same time, none found).
* Took out both RAMs and tried each one in all 4 memory slots individually.
* Booted without any RAM which causes PC-speaker to beep, this indicates to me that the problem doesn't lie with the mem slots part of the MB at least.
* Tried booting up with EZ Flash 2 (press Alt+F2 during boot), but no change at all, still simply no video and apparently no POST.

I have no other DDR2-RAM at home right now, so I haven't tried that, but will see if I can borrow one stick from a friend later on.

I have searched teh net and found a couple of threads regarding P5B with no POST (exact same problem), but they were all during their very first startup. In my case this system used to work fine until now.

The only thing I can think of right now is that the RAM voltage is wrong but the system oddly enough isn't affected by it until now, and then the CMOS clear didn't affect this setting which is why this didn't help. Although, that is only a guess, does anyone know?

Please, if anyone has any suggestion or experience of this problem I would greatly appreciate any and all help.


Jul 1, 2005
Well, problem is solved, tried a friends RAM-stick and computer booted immediately. Tried both of my sticks again, separately, none worked :(.

In other words, no matter how unlikely it seems, both sticks gave up at the same time. Memory timings were set to 4-4-4-12, which they should support, but I guess that together with a high frequency and slightly increased voltage was too much.

This sparks some questions from me of course, since I'm far from any expert in overclocking.
1. What is most risky to the memory, meaning risk of destroying it, of timings, frequency and voltage?
2. As a follow-up to Q1, is it better, in terms of safety, to keep the memory frequency a bit lower and timings at the specified 4-4-4-12, or the other way around (lower timing, higher freq)?
3. These memories specified voltage was 2.1v, how much, approximately, is it ok to increase that value without causing any damage?


Mar 23, 2006
Boot up your PC with your friend's RAM, set the timings to something really loose, like 5-5-5-15, and undervolt them to 1.9 or so. Also remember to remove any FSB overclocks. Then put your Ballistix back in, and try booting with relaxed timings and voltage. If it boots, run a Memtest from a bootable CD overnight and check them for errors.

If that doesn't work, it's possible that your RAM is fried and you'll need to RMA and replace them. Unlikely, but possible.