Can FSB be set to any number, providing you dont exceed the limit?

corkyo4

corkyo4

corkyo4

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Hi,

I want to oc my E8500 to 4GHz. i have the multiplier set to 9.5.

so to get to 4Ghz i need the FSB to be 422mhz.

Upto now i have gone as far as 400mhz for the FSB based on the overclocking guides.

Basically all i want to know is can the FSB be set to any value providing you dont exceed the limit. Or is there a formula you need to use to calculate specific values???


Thanks

Tom
 
FSB can be whatever you want, just depends on whether the board and chip can take it. The E8500 should do 4ghz easy.
 
Best way to think of it is say the motherboard only supports 333 (1333 fsb) then anything over that will be above spec aka overclocking it. Some mobo's support higher fsb's by overclocking only, and not naitivly. You will come to a point where ur fsb just won't go any higher, but thats differenet for every mobo out there.

As an exampe my mobo nativly supports 400 (1600sfb) cpu's, but i have had my fsb upto 500 (2000fsb), it really all depends on what ur mobo supports, and if its overclocking friendly.

Just one thing to remember when you try later, if you are running 800mhz memory, you will have to run the fsb:memory in 1:1, but if you have 1066+ memory then just make sure it runs at a ratio that gets it close to your memorys rated speed.

Have fun.
 
I do find that FSB that are divisable by 8 are most stable - but as reflux rightly said any number is ok on most new boards.
424 should be perfect.

Edit: good point bifday2k - upping the FSB also OC's the Ram, but most 800mhz stuff will hit 848 at stock values
 
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Ok, thanks for the info.

One other thing i was going to ask on a new thread but since you have touched on it.

I have Corsair DDR2 memory 1066mhz think the timings are 7-7-7-19 or something similar. Cant remember off hand.

Anyway my mobo bios (Asus P5QC) allows you to set the DRAM frequency direct as in at 400mhz FSB i can select 1066MHZ frequency. This doesnt exceed the memory speed therefore i presume it is ok.

And so i expect to do the same usuing 424 fsb. I just select a frequency that doesnt exceed 1066.

Anyway my question relates to Ram dividers. i have read up on these at tomshardware overclocking guide. But i just dont get it. I have my machine running at 1:1 according to CPU-Z

But it suggests that you can have different ratios. Should i just go along with selecting a DRAM frequency that is closest to 1066 but doesnt exceed it. Or should i be thinking about the DRAM dividers in more detail??

Hope this makes sense

Thanks

Tom
 
yeh most will, unless really crap generic stuff, mine will run at 1000mhz was'nt i a lucky boy when i got it, just bought it not thinking about overclocking lmao.

Also to corky 4ghz on that cpu should be managable with well under 1.3v (in bios) vcore mobo dependent obviously, as every mobo is diff.

If he was to do the 8 multi he would need 500fsb, and well without knowing his complete setup, no idea if he could manage that. Id stick to the 424/425 option for now myself.

Edit:
For ease of doing it yeh, just stick to selecting a dram frequency thats closest to the 1066 speed, if u want ur memory running at full speed that is, ofcourse after entering the new fsb first.
 
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Any integer number can be requested, those over 500 are unlikely to work without considerable dedication.

Setting different ram speeds is using different ratios. 1:1 at 424fsb will be ddr2 running at 848mhz. This is the slowest you can ask the ram to run, and likely the most stable. The next ratio may be something like 1.25:1, which will run the ram faster. The ram will run over 1066mhz, and possibly under 7-7-7-19, but stability testing if both cpu and ram are overclocked is a minefield. On G35/P45 I set the ram to 1:1, take the processor to the highest frequency I can, then work on the ram with the processor on the quickest "round number" below the maximum frequency.

What motherboard are you using?
 
Mobo is an Asus P5QC

At the moment i have the CPU clocked to 3.8GHz and i have temps of around 30 degrees

i appreciate overclocking takes time but i am not one to go to the ends of the earth to get things running absolutely perfectly. But i would like to squeeze good performance out of it.

It seems a shame to have 1066mhz ram if its only running at 800mhz, however if it is stable that is key.

Would there really be that much of a difference in performance by pushing the ram closer to its limit?
 
Usually the lower u run ur memory speed wise the better the timings you can use.

For example @800mhz i can run 4,4,4,10 (12) but over 900 i have to use 5,5,5,15, and for 1000mhz i have to use 5,5,5,18.

Different applications like bandwidth (speed) others react better to timings, personally i allways try and run my memory as fast as they can go, at there best timings so u get the best of both worlds.

But if your not comfortable messing with memory stuff, then just stick the ram divider so it is as close to 1066 as it will go (fsb dependent). And let the mobo sort the timings for it.

As jon said both memory and cpu tweaking at once is a pain to do. Once we have your cpu sorted we can move on to the memory if you want. For now i would'nt worry about it, aslong as its running under 1066 all will be fine.
 
Ok i now have my machine clocked to 4GHz (9.5 * 424)

DRAM Frequency is 1063 (i think, but the max it can go before exceeding the 1066)

VCore is at 1.31

I ran prime and got an error 3 mins in, so i restarted and upped the vcore to what it is now (1.31 and still i get an error)

Is it worth reducing my memory speed?? or shall i increase my vcore??
 
Ok 2 options really.

Option 1:
Lower the ram speed to the lowest it will go will be like just under 850, to double check its not the ram. I don't think it is, but never a bad thing to double check.

Or

Option 2:
Leave the ram as is, and try abit more vcore volts. Its most likey this option will be best, but all depends how u want to check things really.
 
Ok,

i decided to reduce the DRAM freq to the next setting below, around a 1000. I then had 2 freezes and an unplanned restart.

So, i have set the DRAM freq to auto for the time being and reduced the vcore to 1.27.

Now i know you said to increase this, but prime is so far running ok.

So maybe my memory is being stubborn??
 
Mmm sounds like could have been a timing issue on the memory then, if auto sorts it, as all auto does is read from the spd chip on the memory and goes by those standard timings.

If prime large dos'nt fail for abit, stop the test and start blend test, this will test everything out, and if no crashes on blend then its all fine.
 
seems to be running ok, i havent run prime for very long although i did forget that it was running whilst gaming, and things didnt mess up so.

Anyways thanks for the help all, ill continue to fiddle with the vcore to see if that will go any lower. But my max temp on the cpu is only 56 degrees under gaming+prime so im pretty happy.
 
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