Hi to all. I built a new rig 2 months ago with the folowing:
- P5K Premium
- E4500
- XFX 8600GT
- 2GB DDR 800
- Samsung 320GB SataII
It has been working fine up until 5 days ago. I was using BIOS 0302, with C1E disabled, FSB 255x11, 1,288v...
One day it begun to have trouble POSTing like many other p5k´s that we read about. After trying a lot of different things it started to POST again (90% of the time!). One of the things that I did was to update to the new BIOS 0504 using ASUS Update (I know, I know it was risky!). After runing for a while without any issues I went back to the BIOS to go back to my original oc and back to AHCI mode. As I rebooted I noted that the FSB was the only variable that did not change. I tried going back to Auto then back to manual... no luck the FSB stays at 200. After messing with this for a while I found out a couple things about my board (prob true for other ASUS P5K´s). When you reboot after changing Voltages, FSB, dividers, or after a "Overclock Failure" it will go OFF and then ON again, instead of just rebooting like when you change other settings that don´t need a power off.
The problem was (IS) that if I change just the FSB it doesn´t power off, therefore it doesn´t change it. So what I did was make it think it had a "Overclock Failure". I went in the BIOS and hit "Exit and Save Settings", and when it rebooted I turned the PSU off. When I turned it back on it gave me the "Overclock Failure". So I went in the BIOS, changed the FSB and "Exit and Save Settings". It powered off and on ... and the FSB change stuck!!!
It´s been working but I would like a permanent working solution, something that makes it easier to change the FSB, like it used to be.
- Shoud I flash my BIOS again (0504)? The only thing that doesn´t seem to be working is the FSB thing and the ocasional no POST.
Any input would be greatly appreciated!!!

Weird. Never heard about a problem like this before. Try 266FSB.

as to the title of the post : 200 MHz is the default fsb for that processsor. Its supposed to be that way. If the p5k board doesn't like the settings, it wont show anything on reboot. The power all the way off and back on after setting an overclock or voltage setting is normal - by design. If the system is off, press the power button, it may do a surge start, stop, then post. This is also normal. Set everything to auto, save, reboot, power all the way off, back on and start fresh with those things in mind.

Thanks for the replies!! I know that 200 is the default fsb. What I meant was that if I set it manually to something else (202, 205, 210, 250, 255, 260...) it won´t stick (after reboot) because the computer isn´t powering off and then on like it´s supposed to after such change in BIOS. It´s just rebooting without going off. This only happens with the FSB setting, everything else, including voltages and memory dividers work fine (but the memory ends up being underclocked since the FSB doesn´t change). I already tried setting back to default, clearing CMOS, battery out, FSB Strap 266 (if that´s what you mean Shadow),... I´m not sure if I need to flash my BIOS again. If the update was "bad" wouldn´t be more problems and not just the FSB settings?? Anyone ever had a problem like this - FSB changes on BIOS don´t work????

Yes, I meant the FSB strap. And yes if it was a bad flash you would probably be having more issues. Also try putting in a new CMOS battery. Weird I know, but come to think of it this has happened to me before (with a DS3R) and putting in a new battery solved the problem. Might be worth a try, the battery's are like $3 at RadioShack,etc.

The battery is a CR2032
http://www.radioshack.com/sm-cr203 [...] 62105.html
^$5 you could find it cheaper at your local stores.

Today I found out something else. If I turn the psu off for a few minutes than on, it usually POSTs with the right configuration. But if I let the psu on, it doesn´t POST. I will try the new battery for sure.
I appreciate the link but I´m from Brazil and we don´t have Radio Shack here!!! I will get it tomorow though... but for now I think I will check it with the multimiter to see it´s voltage... thanks again for all the inputs.

update - Battery is reading 3v, so I think it´s not it. The only way I can have an OC is to turn it on > go to BIOS > Restart > Turn it Off as restarting > Turn on and get "Overclock Failure" message > Go to BIOS > Exit and Save. Then it runs perfectly!
I even took my processor out and checked the pins, seemed fine. If this was happenig 2 months ago (when I built it) I would´ve gessed some kind of lack of BIOS support for my memory (Markvision DDR2 800 - i´m running it at ddr834, 1,9v, 5/5/5/15), but it ran great from day one until about a week or so ago. Oh well, it´s a good thing I don´t turn my pc Off very often!!!

I THINK I got it!! After busting my head for a week I decided to start from scratch. Took everything out of the case and started with the basic (mobo, CPU, speaker) and kept adding stuff after testing each configuration for a couple of minutes. The thing that made this problem so hard to solve (for me at least!) was the fact that it was intermittent. It would work fine for a few minutes (a few restarts changing FSB at BIOS), then I would add something else and it would work for a few more minutes, then it would get stuck again. I would then remove what I added last and it would still not work!!! After going back and forth with pretty much everything on my PC, from floppy to USB and Firewire brackets, I came to the conclusion that it was my Fax/Modem which has an Intel chip!!! So I reassembled everything back in my case again (without the modem), and at the very first power on it did not POST !!!
The only thing that I had not tested were the fans, so I decided to check all fan wires to see if they weren´t pinched and therefore shorting out. It was a long shot since they were all working fine. After making sure they were all fine I decided to extend my search to all the wires I could find! When I was checking the front panel wires (power led; hdd led; stand by; reset; speaker) I found a small cut on the positive wire of the Stand By wire! It probably got pinched when closing the case´s side panel at some point. Since the wire itself wasn´t damaged (just the insulation?) I used some electrical tape to protect it. My guess is that the bare wire was touching the metal case somehow, because my PC has been running fine after the "fix"!!! It has only been a day so I´m trying not to keep my hopes up, but so far it´s working. Well, hopefully it´s fixed now, and may this serve as information to whoever get some kind of intermittent problem.

P.S.-I was also getting some weird CPU usage problems before. Sometimes when I closed some application my CPU usage would get stuck at 50% and when I checked Task Manager that application was the one responsible. Don´t know if it´s connected, but it has not happen again yet.

Edited: The CPU usage problem was not related to the wire (it figures). It happens with every application after I play Moto GP URT 3. I uninstalled the game and the problem went away. I will install it again later to see what happens...

P.S.2- First time I´m using Markvision memory and I´m liking it very much. It was the cheapest DDR800 I could find and I´m running it at DDR 1066/5-5-5-15/1,95v. It´s rated at DDR 800/5-5-5-18/1,8v.