basic question about oc'ing

By ArchVile
Oct 5, 2004
  1. ok i uped thee fsb on my athlon xp 2400 from 133 to 140 at 1.65V times 15. when i try to get 144x15, my comp crashes. i asked my friend this but he doesnt know cause he doesnt use AMD cpu's, but when do i lower the multiplier and up the vcore. i mean, how will i know when to do these?
  2. ---agissi---

    ---agissi--- TechSpot Paladin Posts: 1,978   +15

    Ah man be careful! You cant fry your cpu by lowering, uping, chaning, the multiplier or FSB on your cpu in the BIOS, but you can and easily fry your cpu by making the vcore too high. the vcore is the voltage going do the cpu. You'll notice its real fine, as the selection only ranges from like 1.6 to 1.8.

    CPUs all vary, some can overclock more than others, some less then others. Yours (cpu) is crashing when you make it too high because it cannot handle the speed, it may just be the cpu not liking it, or your cooling may be insufficient.

    The fsb speed in your bios shows up as 133MHz and up/lower. Well you have DDR RAM, which is double data rate, and so PC2700 ram, which runs at 333MHz, shows up as 166 in the bios. Notice 166x2 = 266mhz, since its double data rate/DDR ram.

    To get the speed of the cpu, its FSB (times)/x/* Multiplier.

    133(fsb)*12.5(multiplier) gives you 1662.50MHz :)

    You can make your cpu go faster, by raising the multiplier, raising fsb, or both.

    Lets say your stock fsb is 266MHz, and your ram is PC2100. That means your ram runs at 266MHz stock. The ram operates at the same speed as the front side bus. When you raise the fsb to 270mhz (from 133 to 135 in the bios), your overclocking the cpu, and the RAM! so your cpu may be able to take the overclock, and the temps may be fine, but because of your ram, it may not be able to take the overclock, and thats making the system unstable/crash.

    So what some people do to get around that, is they keep the fsb at stock, so you dont have to factor the poor ocing ram into the equation, and you raise the multipler. But you can only do that if your cpu is unlocked. IS your cpu unlocked? If you dont know, the answer is no. The bios may be letting you change it to "15", but it isnt really changing the cpu multipler to x15. Look at the speed on the start up screen of the cpu.

    Only catch is, you get more performance, by raising the FSB and ocing the cpu, than keeping stock fsb and raising multipler to oc the cpu. cuz when u raise the FSB, your ocing the ram and getting more juice there, and so fourth. Just raising the multipler, only ocs the cpu.

    Some people to get around this, buy lets say PC3200 ram for their 333MHz fsb/PC2700 speed cpu. That way, when your running stock, the PC3200 ram is actually being underclocked to PC2700 speeds (since it runs at the same speed as the fsb of the cpu). then when they go to OC, they can raise the multi to 355mhz, and they're still underclocking the ram, the ram isnt going to be a problem with ocing cuz underclocking it of anything wont be it any less stable.

    Heres a table for you with fsb speeds for ram:

    PC2100 = DDR266 = 266MHz [fsb] RAM
    PC2700 = DDR333 = 333MHz [fsb] RAM
    PC3200 = DDR400 = 400MHz [fsb] RAM

    Some peeps, lower the multipler, and they raise the fsb tons since that really helps performacne on top of OCing the cpu, that way the fsb can be super duper high without going beyound the cpu's clock limit.

    So lets say they have a 2500+, thats a 333MHz FSB cpu (166mhz in the bios for its fsb), it runs on PC2700 ram, with a 11x multipler stock.

    You can buy PC3200 ram, lower the multipler to 11, and OC it to a 3200+'s fsb, which is 400mhz. Rraise the fsb from 166 to 200, and lower the multi to 10.5, or 11, so you can have the huge fsb boost without making the cpu OC beyond its capabilities, to give you 200x11= 2200MHz, ala, 2.2GHz :D

    I am by no means a pro at overclocking, hopefully I didnt give out any false information, maybe we can get Veh to read this. I dont have time to proof read this completly, i g2g, but lemme know if this helps at all.
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