Extreme Underclocking

[nevbie]

How slow can you make a modern Intel system running a dual or a quad by using BIOS settings only?

If you set the lowest available frequency values for CPU, FSB and memory (which probably equals FSB in this situation, with recent intel chipsets), can it cause any kind of system instability or damage to the components?

Is the situation different with GPU underclocking when it comes to instability/damage?
At least the PCI-E clock/PCI clock will cause problems when running too fast. Does the same apply for running a "too" low frequency?

If you halve the memory clock, can you also halve the memory timings, and still run stable?

 

[Idontcare]

The BIOS's I have seen don't let you manually set the FSB below 4x200 = 800MHz.

Intel's Conroe series have a minimum multiplier of 6x.

So 6x200 = 1200MHz or 1.2 Ghz.

There may be mobos out there that let you underclock the FSB below 4x200.

I suppose you could dig out an old 965 board with 4x133 = 533MHz FSB support or even 4x100 = 400MHz FSB and see if it lets you use those P4 FSB speeds with a modern Core2 chip.

Obviously my references here are Intel systems. I have no recent experience with AM2/AM2+ to know how much you could underclock an X2 or a Phenom.

 

[Zap]

Idontcare seems to be spot on regarding Conroe overclocking with 6x CPU multiplier low-limit and the motherboard low limit of 200/133/100MHz FSB.

Regarding AMD A64 chips, I think the lowest multiplier is 4x, and the only HTT speed is 200MHz (before overclocking) so 800MHz is minimum.

I don't see any issues with running CPUs underclocked as none of them will push bus speeds out of whack, as in the PCI-E (and all other busses) will still run at the appropriate speeds.

Regarding memory timings, I don't think there is a set rule on how it links to frequency. Indeed (at least with DDR) some RAM can hit high frequencies but cannot hit low latencies, while other, low latency RAM can't hit high frequencies even with lax timings.

With DDR2 the lowest you can run it at would probably be 400MHz CAS 3.