can't OC unless I increase PCIE speed too

OK, I have a very poor mobo for overclocking, but this doesn't seem right.

It's an ASROCK Wolfdale1333-GLAN/M, with an Intel E2140 and 1GB OCZ DDR2 2700. I bought it for a HTPC so overclocking was not on my mind, but the CPU is meant to OC well so I thought I'd give it a go. What I find is, upping the FSB from 200 to 250 while leaving the PCIE at 100MHz, it won't boot at the increased speed, but sticks at the stock 1.6GHz (8x200). But if I set the PCIE bus higher, to 110, it boots fine and I get a stable overclock.

This isn't normal is it? Why should the PCIE speed affect whether it can overclock the CPU? I think I could go a lot higher with the CPU, but I'm afraid to overclock the PCIE bus, I might break it!

Any thoughts (other than "get a better mobo, cheapskate")?

J

Well something's got to join the two together somewhere, so I'm not totally surprised that you get syncronisation problems on some chips if the PCI-E clock differs massively from the CPU clock.

I think the PCIE bus is always 100, while the FSB can be all sorts of things. All the overclocking guides I've read suggest uncoupling them and keeping PCIE at 100, while tweaking FSB, and the mobo supports this so I don't think it's a full explanation.

Well , you don't have to lock it at 100' think you can have it anywhere between 100 and 110 ( i maybe wrong saying that ) but I raised mine to something like 108 and did not have any problems. It's just that it is the recommended thing to do when doing an o/c . If it is not causing you any problems well leave it at 110.

the only problem it's causing is I can't go beyone FSB 240 without upping the PCIE beyone 110 and I don't think that's a good idea. Don't understand why it's a limiting factor.

Are you 100% sure it's the PCIE speed that's really limiting you? Have you tried running a lower divider on the RAM?

I have the same issue on my Asrock ConRoe1333-D667 board too!! This uses the same Intel G945GC A2 chipset as the Wolfdale1333-GLAN/M. I can only overclock stably if the PCI-E frequency is increased. Also it states this limitation on the Asrock website for both boards.The cheaper boards tend to have this limitation as with better boards you can lock the PCI-E frequency at 100mhz and still overclock reasonably well.

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Originally Posted by CAT-THE-FIFTH

I have the same issue on my Asrock ConRoe1333-D667 board too!! This uses the same Intel G945GC A2 chipset as the Wolfdale1333-GLAN/M. I can only overclock stably if the PCI-E frequency is increased. Also it states this limitation on the Asrock website for both boards.The cheaper boards tend to have this limitation as with better boards you can lock the PCI-E frequency at 100mhz and still overclock reasonably well.

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That's interesting, have you got a link? I saw it ups the PCIE to 115 in order to get FSB=1333 but I'm only on FSB=240!

Anyway, assuming this is a hard limitation, how high is it safe to go with PCIE bus speed?

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Originally Posted by JohnK

That's interesting, have you got a link? I saw it ups the PCIE to 115 in order to get FSB=1333 but I'm only on FSB=240!

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FSB is quad pumped CPU clock, so 240 = 960. But your CPU clock should be able to get to 333mhz without a problem.

Maybe there's just a hole - try 266mhz and see if that works.

OK I figured it out. The problem is that the chipset has an overclocking lock, apparently most 945 boards are the same. You can take the PCIE up to about 120 before losing SATA and the gfx card. Shame they tempted my by putting the ability to lock the PCIE to 100 in the bios, it's actually useless. At PCIE 120 I should be able to go up to about 270 on the CPU at least.

This would be less of an issue if my CPU had a bigger multiplier, but it's 8x so I don't get much out of each MHz. You live, you learn.