Adding 6GB RAM to an OC Bundle?

Festisio · 7 Mar 2010 at 00:43

Evening,

I bought this bundle a few months back:

OVERCLOCKED* Intel Core i7 920 D0 Stepping (SLBEJ) 2.66Ghz @ 4.20GHz Max / Asus Rampage II Extreme Intel X58 Motherboard / Corsair XMS3 6GB (3x2GB) DDR3 PC3-12800C9 1600MHz DDR3 Bundle

I'm just wondering about the logistics of adding 6GB more of the Corsair XMS3 RAM.

I'm not massively clued up oo the OC'ing angle, but I believe some aspects of the OC would need to change if I was to install 6GB more.

Can anyone advise?

thanks

JonJ678 · 7 Mar 2010 at 00:53

Yeah, the cpu clockspeed is probably going to go down, and the ram frequency definitely will. Look for 4.0ghz cpu, 1200mhz ram after a fair amount of time spent tweaking. It's possible to do better than this, but rare.

If you don't need the additional 6gb, stay with what you have now. It'll be slower if you put more ram in.

Festisio · 7 Mar 2010 at 00:56

JonJ678 said:
Yeah, the cpu clockspeed is probably going to go down, and the ram frequency definitely will. Look for 4.0ghz cpu, 1200mhz ram after a fair amount of time spent tweaking. It's possible to do better than this, but rare.

If you don't need the additional 6gb, stay with what you have now. It'll be slower if you put more ram in.

1200mhz you say! I seem to currently be on much lower than that

A picture paints a thousand words as they say

The reason I'd like more RAM is I'm doing more VM work than I initially thought and it's surprising how quickly 6GB can be eaten up iwth a few of them running.

cmndr_andi · 7 Mar 2010 at 01:02

You are running your RAM at 766MHZ, and due to DDR (double data rate) that is 1532MHz.

Therefore 1200MHz would be slower. However, due to the massive memory bandwidth offered on the X58 I doubt you will receive a performance penalty if dropping down to 1200Mhz.

JonJ678 · 7 Mar 2010 at 01:03

DDR stands for double data rate, meaning 1600mhz ram runs at a core clock of 800, which is shown in cpu-z. The 766mhz displayed in cpu-z is 1532mhz in terms of what's written on ram when you buy some.

Ram runs at a multiplier times the bsck value, this is the 191MHz times 8. So it's currently at 1530ish, moving to 12gb probably means the multiplier has to go down to six. 191*6=1146MHz.

I'm running at 200bsck, 4ghz, x6 ram multi for 1200MHz ram. I've had 4.4ghz nearly stable, but not cracked it yet. I'm also using 12gb of ram for the benfit of virtual machines, the i7 processor does rather well with them.

Beaten ^. He's right though, 1200mhz down from 1600ish doesn't matter so much. Can probably tighten the timings if you want to, 1200 cas6 isn't very different to 1600 cas8 in terms of benchmark performance and I can't tell the difference at all in general use. Getting 4.2ghz from the processor with 12gb installed is much harder than with 6gb installed, it's taking me ages

Festisio · 7 Mar 2010 at 01:19

Thanks for the replies folks, lots of good info!

Strawberry · 7 Mar 2010 at 03:23

Memory speed doesn't affect real-world / gaming performance by much, even when nearly double speeds. Usually applications are hard drive, cpu or graphics card limited.

Festisio · 7 Mar 2010 at 16:45

I'm sure I'll be back once I've ordered these to seek your expert advice re: overclocking since I'm probably going to run into troubles!

King Arthur · 7 Mar 2010 at 17:09

Having tried 12Gb on our overclocked bundles they more often than done fail to work on high overclocks.

The on board memory controller on the CPU's don't tend to be able to handle all 12Gb of memory at high speeds, you may get 3.8Ghz tops but don't expect 4.2Ghz unless you have a godly chip.

Also please note changing the bios overclock settings or adding in more memory will invalidate your 1 year warranty you have on the bundle sorry.

phil

Festisio · 7 Mar 2010 at 23:33

King Arthur said:
Having tried 12Gb on our overclocked bundles they more often than done fail to work on high overclocks.

The on board memory controller on the CPU's don't tend to be able to handle all 12Gb of memory at high speeds, you may get 3.8Ghz tops but don't expect 4.2Ghz unless you have a godly chip.

Also please note changing the bios overclock settings or adding in more memory will invalidate your 1 year warranty you have on the bundle sorry.

phil

And has that specifically been the case on the i7 920 D0?

I am pretty sure I'm not "in tune" enough with my PC to notice a drop from 4.00Ghz to 3.80Ghz so that downside wouldn't bother me per se.

JonJ678 · 8 Mar 2010 at 00:43

This is the case on every processor I know of (775 or am2+ and later). If you use all the ram slots, you put the memory controller under more stress. This invariably leads to lower achievable ram frequencies. For a reason I don't really understand the memory controller being stressed makes life difficult for the processor, so it also doesn't clock as high.

Warranty is voided for the simple reason that if you just plug in another 3 sticks and turn it on, there's a good chance it won't post and a certain chance that it'll be unstable.

My experience with this has been that 4ghz, 6gb at 1600mhz was trivial to achieve. 4ghz with 12gb at 1600mhz was impossible. 4ghz with 12gb at 1200mhz took about a day but is very, very stable. Anything up to 4.4ghz with 12gb at 1200+MHz can be persuaded to pass intel burn test, but freezes on heavy use.