Different RAM types preventing o/c?

Hi all, hopefully someone can shed some light on this problem for me.

Mobo: Gigabyte GA-P965 DS3 Rev3.3
CPU: Intel E6600 2.4ghz dual core, generally overclocks on air to 3.6ghz for many (not me tho, see below)
RAM: Crucial 2GB Kit (1GBx2) Ballistix DDR2 PC2-8500 (bought with PC ~7 years? ago, working fine)
RAM2: 4GB (2 x 2GB) PC2-6400U DDR2 RAM 800MHz Non-ECC 240Pin PC DIMM Desktop PC
Thermalright Ultra120 heatsink w/140mm fan, aero-cool turbine case, i.e. good air cooling

I'm trying to OC my rig from factory (2.4) to ideally 3.6, failing that 3.4, 3.2, whatever. I *think* I've successfully OC'd it before but had the auto-throttling on which caused problems, for ages now it's been @ factory. After a few years of having the rig I added 2x2gb budget RAM sticks to the 2x1gb premium sticks I already had. Trying to OC now but it dies immediately and resets back to factory clock.

Settings I'm trying here, from various threads here here here here here here here, and keeping it in the family, here here and here. Passmark memory info here - note total physical memory 3582, total available physical memory 2632. I run linux but I figure that shouldn't matter for the most part since this is all pre-OS BIOS stuff. Nonetheless, in linux (xubuntu), the system might only be recognising 4gb also (see dmi decode 16), despite the indicators elsewhere saying that it has 6gb available and uses it fine.

Can anyone think what the problem might be here? My guess is that the newer, worse quality 4gb sticks have slightly different settings (PC2 6400 vs PC2 8500 for the original 2gb) which the mobo doesn't like? I also saw something about "only shows 3.5gb" in the sticky which might also be related to my problem so I'll read up on that now. I'm minded to take out the 4gb sticks and see what happens, but would prefer to find out first, especially since some games require >2.4ghz clock AND >2gb RAM, and if I take those sticks out I can't have both.

Thanks in advance for any tips, thoughts, questions!

You definitely want to try overclocking with just one of the memory kits at a time. If successful, then I think you have your answer. It's never a good idea to use mis-matched memory. If you want to try using both kits together, then set the memory timings and speed manually to the slowest of the two kits.

Thanks!
I don't know what the numbers in the "PC2-8500" / "PC2-6400U" mean; assumedly higher is better, but if you had to choose, would you take out
A. The newer, cheap, 6400U sticks, that are 4gb total, or
B. The older, better, 8500 sticks that are 2gb total?
(ideally there'd be option C: the older cheaper slower smaller ones, cos then it'd be a no brainer!)

It's the speed at which the memory is capable of running at. If you don't know what those speeds mean, then my guess is you have never properly set them up to run at their rated speeds anyway. I would probably go for the 4 gb kit for more available memory. You should be able to overclock the CPU and still keep the memory speed at it's rated speed, which you'll probably have to make sure of because that "cheap" set might not overclock at all.

Thanks again. Interesting, so the mhz is clock speed (both are 800), and the 8500/6400 is a different speed metric? For ref I have set the mhz in the BIOS; pretty much all of the setups from the boards have the sticks at 800mhz which both these stick types support so that shouldn't be a problem. Thanks man, I've give it a whirl tonight. Have a cracking weekend.

Both are not 800Mhz though. You may be running there, but your sticks are different speeds. The 8500 and 6400 refer to their stock speeds with PC2-8500 being 533Mhz(1066 DDR) and PC2-6400 being being 400MHz(800Mhz DDR).

aaaaaaah! Dude! Thank you, that makes so much sense then, i.e. by multiplying the RAM speed by a single multiplier (the only option) e.g. 2 I'll end up with 1066 & 800 with the 1066 being capped to 800 but causing problems.
So my bad for not knowing this when I bought those sticks then. Damn it, £9.50 down the drain argh!

Ok cool, thanks guys, hopefully this'll sort me out this weekend then.

DDR = Double Data Rate.


I doubt the 1066(PC2-8500) sticks are having trouble running SLOWER than its rated speeds though. Just the mixing and matching may be doing that.

I am with Lvycoyote though, run whatever is 4GB, not 2GB.

Thanks again guys. Took the 2x1gb sticks out & trying to get it going now but no matter what I do (other than auto settings) it won't post. I don't suppose you can see where I'm going wrong can you? I'm trying increasingly conservative OCs, loosening the memory timings, lowering the vcore, and still nothing. Link to my workbook here, yellow highlights are the changes at each attempt. Many many thanks in advance.

Edit: ugh, turned out the external usb hard drive was preventing it from booting, god knows why, but now have it at 7x400=2.8 w/ loose timings & minimal overvolting, and will aim upwards from here!
Edit2: stable @ 3.2, 8x400 @ 5/5/5/15 w/ +0.3vdimm & 1.375vcore. Pushing to 3.6 (9x400) boots to OS (xubuntu) but lots of stuff crashes. Will try tightening memory timings to 4/4/4/12 & upping MCH to +0.2 & vcore to 1.45v. Any other tips appreciated - I'm struggling to find anyone with my setup posting their full settings from their 3.6ghz OCs on air...