help with overclock

only thing not overclocked is the cpu.

i want to overclock it but encountering problems instability etc when i hit 189*2 fsb while 166*2 is normal max.

my mainboard doesnt have any pci/agp or memory locks on it tho the pci/agp frequency isnt a problem the memory may be.

as it is ddr266 running at ddr333 speeds which is my cpus default speed the mem is set to a 1:1 ratio witht he cpu at moment an running on looser timings.

now it could just be my mem doesnt want to overclock any higher or it could be my psu as i have just noticed my 400 watt cpu has only 17 amps on the 12volt rail and 40 on the 5 volt rail.

i was wondering if thats the reason i cant overclock cpu an extra 200-300 extra that is when my room is cool and ambient pc temp is cool also along with cpu temp i have heard of my cpu hitting 400fsb with ease.

basically is it the psu or the memory getting pushed to far or a combination of the 2 or even my motherboard just sucks for overclocking tho ive heard of that board an cpu hitting 190 no probs... im confused what is stopping me overclocking cpu...

here is my specs :

gigabyte ga-7vaxp via kt400 mainboard
mercury 400 watt psu
amd sempron 2800+ @ 2ghz, 333 fsb
twinmoss 512 ddr 266 @ 333 fsb
geforce fx 5900xt @440/770
audigy 1 sound card
ibm hardrives 40 gig an 13 gig 7200rpm
samsung harddrive 160 gig 7200rpm
philips 52x cd writer
samsung 16x dvd drive
Thermaltake xaser v case http://www.thermaltake.com/xaserCase/WinGo/v7000d.htm

I have not messed around with overclocking that much...but it sounds as if your memory may be the thing holding things up. You already have it OC'd up to 333MHz which puts a bit of thermal and electrical stress on it. I would say a general rule of thumb for overclockable memory is: get a name-brand with proven reliability that is rated at or faster than you actually need. (for example: get DDR400 if you want to overclock to 400MHz from 266MHz) Pretty much any decent brand of DDR memory will be backward compatible with lower speeds (as long as the generation and pin count are the same of course :) )

You may also want to search for reviews of your motherboard on google. Every motherboard has a limit, and other overclocking gurus may have had similar issues with overclocking and may have discovered the solution.

thanks for ur reply tho i now beleive its trhe mother board stopping the overclock had it running at 174 pretty smooth when my rooms been cool not willing to overclock higher than that till i get a better cpu fan tho im sorted for thermal pasted my m8 brought some arctic silver 5 up the other day :)

the mem seems to be ok at high overclocks so its now a factor of the mainboard and the psu :)

the ram is running at 1.6 volts which is stock :)

I've never tried overclocking a Sempron (though I'm sure it's not too much different considering it's based on the T-bred core). What is your cpu core voltage set at? Even though you say that the RAM is running fine at overclocked speeds, I would definitely suggest buying some DDR-400 anyway. The less stress on the system the better. If you're concerned about cooling though, it probably isn't a good idea to adjust the voltage until you get a better heatsink and fan. Btw, may I ask what the cpu temperature averages before any form of overclocking?

The core voltage and the proper speed RAM is what helped me though. I'm running an Athlon 2500 at 400 FSB which overclocks to 3200 speeds. Core voltage at the moment is at 1.7 volts.

EDIT: After reading some reviews of the board, it seems that it isn't a favorite for overclocking though it has many nice features. Especially considering that you have voltage modifiers that are based on percentage which may not allow you to reach a stable overclock. Although I would think 1.76 volts would be enough for a stable overclock.