Intel 640 Stability Question

Ok, so I've been running a very stable box at 245x16, but my temps were never really that high so I wanted to test higher OC's...

250x16 works pretty well, but if I go any higher than that I lose stability.

My question is (keep in mind I'm a big OC noob) why do I lose stability? Cause I don't think my CPU is getting that hot (as I've NEVER seen it throttle while logging with ThrottleWatch) but if I try to run two instances of Prime95 doing a 192K in place torture test, my machine restarts after like 30 minutes.

I have 1024 MB of Crucial DDR-400. I'm running it at a 5:4 ratio (which would be a slight overclock at anything above 250 FSB... Nothing huge at like 255 FSB though)

So yea, why am I not stable? Is there something other than heat that makes a system unstable? Is my RAM not capable of going a few MHz over 400? Do I need to up my VCore (I've been leaving it on "auto" in the BIOS)?

Throttlewatch reports my CPU voltage at an obviously incorrect 1.963
CPU-Z says I'm at 1.523
ASUS Probe says 1.36

I guess I should include some system specs
ASUS P5GDC-V Deluxe Motherboard
Intel Pentium 4 640 with Zalman 7700CU with AS5
Radeon x800XL
Some optical drives and hard drives
A ThermalTake V5000A (Has a bunch of fans in it)
And a 500W Rosewill PSU (Has a whopping 34A on the 12V rail)

Again, my CPU has never reached a temp that TM1 kicked in and throttled it, so it's definitely not running too hot.

Thanks in advance for the help. --Lutzy

MAaybe you've just reached the limits of what your CPU will do.

how hot is the northbridge chipset getting?

Lutzy said:

Do I need to up my VCore (I've been leaving it on "auto" in the BIOS)?

Click to expand...

That would be my guess - My 640 ran no probs to ~4G on "auto" Vcore, then I had to set it manually to get a higher OC. I'd also bump Vdimm up a bit, too, and the voltage to the NB, also (not sure how the NB is/could be done on i915/925 Asus mobos - I have an LGA7775/i865P Asus hybrid).

Throttlewatch reports my CPU voltage at an obviously incorrect 1.963
CPU-Z says I'm at 1.523
ASUS Probe says 1.36

Click to expand...

I have a different mobo (P5P800), but the same cpu & reporting problem as you. Might be something to do w/the 640's EIST technology. I'd trust the BIOS readings & AsusProbe (mine are both very similar) over CPU-Z. CPU-Z reading high Vcores on Asus LGA Pressys has been pretty well documented, by now. Not sure if it's only an Asus thing, but many peeps have seen it on Asus mobos.

BTW - You may want to disable a BIOS feature called 'C1E'. This disables Intels EIST function, and may allow more stability on high OC's, since your not transitioning multis during load changes. But doing this will keep your cpu at the 16X multi; irregardless of load, it will never auto-multi back down to 14X.

GL

Strat

<EDIT>

Hey, I just looked up your mobo & found its a i915. Does it have a PCIe/PCIe16 lock??? Sure hope you've got it locked down!

Know Nuttin said:

how hot is the northbridge chipset getting?

Click to expand...

Hi Know Nuttin -

Good question.

The guy will have to answer for himself, but I've found a Zalman 7700 series (or even a 7000 series), does an excellent job of keeping the NB cool, w/the Asus stock passive NB cooler. Especially when running the Zalmans wide-open (as anyone w/a significant OC probably always should, IMO).

I never realized this, 'cuz I always ran Zalmans, and wondered why peeps were so concerned w/active NB cooling - Then one time I switched to a different HSF where a Zalman had been - Yowsa'!!! That NB was toasty, baby!

Never even knew I was coolin' my NB's w/those Zalmans!

Duhhh...

Strat

Stratcat said:

That would be my guess - My 640 ran no probs to ~4G on "auto" Vcore, then I had to set it manually to get a higher OC. I'd also bump Vdimm up a bit, too, and the voltage to the NB, also (not sure how the NB is/could be done on i915/925 Asus mobos - I have an LGA7775/i865P Asus hybrid).

I have a different mobo (P5P800), but the same cpu & reporting problem as you. Might be something to do w/the 640's EIST technology. I'd trust the BIOS readings & AsusProbe (mine are both very similar) over CPU-Z. CPU-Z reading high Vcores on Asus LGA Pressys has been pretty well documented, by now. Not sure if it's only an Asus thing, but many peeps have seen it on Asus mobos.

BTW - You may want to disable a BIOS feature called 'C1E'. This disables Intels EIST function, and may allow more stability on high OC's, since your not transitioning multis during load changes. But doing this will keep your cpu at the 16X multi; irregardless of load, it will never auto-multi back down to 14X.

GL

Strat

<EDIT>

Hey, I just looked up your mobo & found its a i915. Does it have a PCIe/PCIe16 lock??? Sure hope you've got it locked down!

Click to expand...

How do I lock them?
They're all set to auto except PCI which I froze at 33 MHz.
What should I lock my PCIe16 to? --Lutzy

Lutzy said:

How do I lock them?
They're all set to auto except PCI which I froze at 33 MHz.
What should I lock my PCIe16 to? --Lutzy

Click to expand...

Sorry, I can't answer that, 'cuz I don't own an i915 mobo - I own an Asus P5P800 which is an LGA775/i865 hybrid. I do remember lots of peeps having troubles OCing the early i915/925 mobos cuz the gfx PCIe didn't lock, but rose w/the FSB. Eventually, the gfx card would limit the OC. Batboy had this problem on this forum, IIRC. It took a while 'till the Asus 'XE' boards came out, IIRC, before there was a solid PCIe16 lock. If you've got PCIe & PCIe16 options, 'auto' may keep 'em locked at thier design spec frequency, but I'd manually choose the correct frequency, if you have the option.

You're gonna' have to wait for someone that's got a i915 lockable mobo to chime in, do a forum or google search, or start a new thread with this specific question.

Best I can do - But the gfx card has to be locked, somewhow, if you wanna' go past 250 - Hopefully 'auto' already does it on your board. Maybe ask in the Asus mobo section.

Sorry I can't be of more help...

Strat

Stratcat said:

Sorry, I can't answer that, 'cuz I don't own an i915 mobo - I own an Asus P5P800 which is an LGA775/i865 hybrid. I do remember lots of peeps having troubles OCing the early i915/925 mobos cuz the gfx PCIe didn't lock, but rose w/the FSB. Eventually, the gfx card would limit the OC. Batboy had this problem on this forum, IIRC. It took a while 'till the Asus 'XE' boards came out, IIRC, before there was a solid PCIe16 lock. If you've got PCIe & PCIe16 options, 'auto' may keep 'em locked at thier design spec frequency, but I'd manually choose the correct frequency, if you have the option.

You're gonna' have to wait for someone that's got a i915 lockable mobo to chime in, do a forum or google search, or start a new thread with this specific question.

Best I can do - But the gfx card has to be locked, somewhow, if you wanna' go past 250 - Hopefully 'auto' already does it on your board. Maybe ask in the Asus mobo section.

Sorry I can't be of more help...

Strat

Click to expand...

Do you know what frequency the PCIe is supposed to run at? Cause I can force it to stay at that if I want. --Lutzy

Default PCI-E is 100 MHz. On my old Abit AG8 with i915, I had my best results with an updated BIOS and leaving the PCI-E at auto. But, try it both ways. Seems like most i915 chipset mobos run out of gas between 240-260 FSB.

However, you are still using default vcore if I read the post correctly and Asus is known to droop vcore a little under load, so a bump or two in vcore might really help you. Might bump the vdimm and N/B voltage a notch too.

Thanks batboy, I'll give that a try.

I really should just go buy some new ram... If I had some nice super fast DDR-2 I'm sure this would be a lot easier.

I'll go play around with VCore and VDimm. Thanks for the help. --Lutzy