Overclocking questions...

[point4life]

I'm thinking of getting a 1.8a P4, a SIS 648 mobo (unofficially supports DDR400), and some DDR400. Here are my questions:

1) I sorta understand the whole FSB/memory ratio, but how is a 133MHz FSB/400MHz DDR config possible? The ratio would have to be like 133:200...yet I see reviews of 533 FSB/ DDR 400 configs all over the place. How does this work?

2) From my understanding, when overclocking, one wants to increase the FSB, multiplier, and vcore in that order. Why the vcore last? I've never overclocked before; should I just leave it alone?

3) The last and most basic question: how does one overclock? Gradually increase the FSB until it becomes unstable then max out the multiplier? Or should I concurrently increase the FSB and multiplier? Do you know of any solid overclocking guides?

4) What's the best way of testing stability? Any particular burn-in programs?

Thanks.

 

[gururu]

here is my two cents!

1) at fsb 133, DDR 400 not possible with current cpu/memory dividers (the 648 would have to implement a 2:3)
- DDR 400 only possible (if memory permits) with fsb: 150 (3:4 divider, very motherboard dependent)
160 (4:5 divider, very cpu dependent)
200 (1:1 divider, impossible)

2) multipliers cant be changd on P4s. fsb, then vcore. vcore last since more voltage leads to hotter chip.
if you want more speed, you will inevitably end up raising vcore +5-10%

3) yes, gradually increase fsb to determine cpu limit.

4) read some of the threads remarking on benchmarks. you will eventually derive your own suite of tests.

good luck!

gururu


that's funny, i agree with Mikki completely!

 

[Mikki]

1) you'd have to have a really funky ratio to get that! You can get 400ddr (Corsair XMS3200)and run it with a 133fsb cpu, but at default speed it won't run at 400, you'd have to overclock it.

2) You can't adjust the P4 multiplier, it's locked. So essentially, you would bump up the fsb until it becomes unstable, then bump up the v-core to stablize it out. You could do the v-core first, but it doesn't make sense to do it that way.

3)see above, start reading threads here at AT and here. Try places like overclockers.com for references.

4) the best way to test stability is with Prime95 (check out the software thread that's stickyed at the top of this forum)

And keep asking questions, we're here to help, but we like you to do your own research before you ask the same questions everyone else has posted. Good luck!!!!

Edit: Sorry guru, we musta posted at the same time...

 

[Duvie]

I believe the sis645dx mobo already offers a 4:6 ratio (or 2:3 to most of you) shouldn't be much of a stretch....133fsb would be 400mhz ddr.

Hell they were the only ones to offer 333mhz ddr support at 100fsb with the sis645 mobo and a 3:5 ratio...I took my chip to 120fsb and had 400mhz ddr....

 

[point4life]

Hey, thanks all for the responses. Now that I know the P4 multipliers are locked, I'm wondering if the 1.6A would be better considering its lower multiplier. I'm guessing a 1.6@2.4 w/ 150 FSB would perform better than a 1.8@2.394 w/ 133 FSB. Am I right?

 

[Duvie]

Yes you are right...on a couple of fronts....

The higher the fsb of the 1.6 (600fsb quad pumped) will be slightly better...

Also the higher the fsb means even when using default 1:1 memory ratio you will get 300mhz ddr (pc2400) versus 266mhz ddr (pc2100)...the p4 will respond better with the higher bandwidth....

NOtceable??? In the right apps yes!!!


Get the 1.6 and go with a mobo with a 4:5 memory ratio like the epox 4g4a...You likely can get near 160-166fsb which starts pushing into 440mhz ddr and some pc3200 wont be able to handle it....


If you get the 1.8 likely go with a board withthe 3:4 ratio since 160fsb may be very tugh to reach and yet you could still get 400+mhz ddr...


If you know you are going to get one of the new stepping 1.8 that had the die shrink maybe still go with the epox 4g4a mobo cause if you can get near 3ghz (like I have seen a few) that 3:4 will not be able to help you out and you find youself running much lower ddr.


Hope I helped some!!!

 

[point4life]

Well the motherboard I'm considering (Abit SR7-8x) has 3:3 - 3:6 and 4:3 - 4:6, so I'm not really worried about FSB/mem ratios. I just want to know which proc stands a better chance at stably overclocking to 2.4/2.5 GHz. I'm getting some good Samsung DDR400 memory as well.

 

[Duvie]

This topic has been discussed many times here....A 1.6 or 1.8 are both likley to get to 2.4ghz with may or newer pack dates...order from newegg and you likely can get that...also any other high volume dealer...

The other thing is, the 1.6's have been discontinued however the 1.8's are part of the new die shink and if you get one of those chips you can maybe do 2.5-2.6ghz at defaul vcore with 2.8-2.9 a eal possibility...


My june packed 1.8a (which I am going to be selling) does 2.4ghz at default and maxes out at 2.610ghz with 1.71v (prime tested 8 hours w/ and w/o 387mhz ddr turbo settings)....

I think a newer die shrinked 1.8 can likely come close to the fsb the average may/june 1.6 was getting...


Make sure that board has an agp/pci lock...