Can new AM2 mobos overclock DDR2-800?

ford30066

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Dec 11, 2006
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I am interested in buying a new AM2 mobo and have been considering the following: ASUS M2N-SLI Deluxe, Gigabyte GA-M57SLI-S4. I am new to OC, but have been reading many articles on it. I feel comfortable with looking into OC'ing the CPU, but I am still confused on how to OC the DDR2-800. It appears the ASUS mobo above can set the memory frequence (not sure about the GA) to one of 4 options [400, 533, 667, 800]. An article I read on Tom's Hardware page, said that the AM2 chips will automatically choose and set the clock divider. Most of the articles on OC'ing memory discuss using DDR[1] not DDR2. So how are people taking DDR2-800 memory and overclocking it to 900 and greater? Will the Boards I mentioned above support this? What memory should I buy? Should I buy Crucial or some other brand (I used Crucials memory configurator to find compatible memory). OZC does not appear to be support on these mobos.
 

carod

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I'm not an expert on this by any means but i'll have a stab at answering it :D

The base fsb for your am2 cpu is 200, so on my x2 4200 chip it's base freq (200) x multiplier (11 in my case) to give a cpu clock of 2.20 Ghz. The HT speed is 200 x multiplier, usually 5 to give a HT of 1000 (but 4 x 200 on my nf3 board).

Your ram speed is also based off that base fsb of 200 like so, a ddrII 400 setting will use the base fsb freq but because it's ddrII it's dual pumped to give a resulting speed of 400. A ddrII 800 module would use the base fsb of 200 with a divider of 1:2 (or 2:1 depending on how you view it) to give 400 and again because it's ddrII it's then dual pumped to a speed of 800.

Working all those numbers out by changing the base fsb you can see the results, for example if had your ram set at ddrII 800 and changed the base freq to 250 you'd get 250 x2 (ram divider) x 2 (dual pumped ddrII) to give a resulting memory speed of 1000. This is the reason why people buy higher rated ram modules than their mb openly supports, to give headroom for raising the fsb during overclocking

If you don't oc then get good quality modules at a speed the mb supports because you won't need anything faster. If you overclock then you need to think about how far your gonna try to oc and get the appropriate rated ram. One thing to bear in mind is that if you bought ddrII 800 ram but set it in bios to 667 then with a bit of oc'ing you'd be approaching the rated 800 speed again, this would be a lot cheaper than buying ddrII1000 modules i would think.

I'm not even gonna go into ram timings because they make my brain melt lol

Hope this helped in a rambling fashion and feel free to correct me people, i'm not an expert on this.

Carod
 

ford30066

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Thanks for the explanation. I think I am beginning to understand this. Another question though: I was looking in the manuals for the some different motherboards and noticed that only the ASUS M2N SLI Deluxe had an option to select which speed the DDR2 should run at (400, 533, 667, or 800]. The Gigabyte board did not have this option.

Also, I noticed in other articles on overclocking, they discussed lowering the HTT multiplier as you increase the ref clock so that the HTT does not get to high. Is this done automatically on the new AM2 boards or is there an option in the bios that I am not seeing/understanding from the manuals?
 

carod

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I'd google any mb you were thinking of buying and look for overclocking reviews or read/post in the mb specific section of THG. Most boards these days have some oc potential but if you really want to overclock and be stable i'd look for a good board. As an example my mb is an asrock am2nf3-vsta, it's a budget model and based on nf3 and as such it's fairy crappy at oc'ing, most i can get is pushing the fsb to 218 which results in 2.4 Ghz and a HT of 872 (HT of 800 is stock on my board as it's an nf3). After some investigation it looks like the HT is limiting my oc, i know the x2 4200 can go higher than 2.4Ghz, the ram runs happily at ddrII 800 so has headroom at the ddrII 667 setting i was using during the oc. This is my 'wall' as i can't change the HT multiplier in bios. On the other hand, the mb does allow me to lock my agp at 66 so it doesn't get raised with the fsb increase (anyone remember the days when mb's were really useless and when you changed the fsb you changed EVERYTHING lol)

Sorry i can't reccommend any good oc'ing boards but i don't know any since i've never seriously oc'd, but i do know the DFI lanparty boards are generally hightly thought of in the oc department and should allow you to have control over nearly everything, again try to look at reviews of specific boards before you buy

Carod

and if anyone wonders why i bought a crap mobo it was the only am2 board i could find at the time that had AGP to plug my gainward 7800 GS into