Number of DIMMs and effect on RAM overclock?

[TylerS]

I wasn’t sure if I should put this question here or not – it’s about RAM but in reference to overclocking.

System: C2D e7500 @ 3.93 / GA-P35-DS4 (v.2.0) / 6GB PC 800 Patriot @ 895 / Asus 7870 (stock) / Corsair HX620 psu / Thermaltake Water 2.0 Performer (cooler)

BIOS Settings:
- 3.93 gHZ (358X11)
- RAM @ 895; 5,5,5,15 (Motherboard doesn't allow 1:1 as far as I can tell so the System Memory Multiplier is set at 2.50)
- DDR2 Overvolt: +0.40 (2.2v)
- FSB: +0.15v
- gMCH: +0.125v
- Loadline Enabled
- CPU vCore: 1.36875v
- LinX: 20 passes successfully (set to Max 75C – not hit)
- Prime95: 4(ish) hours w/o errors

My ram configuration is 2 x 2GB and 2 X 1GB. Going any higher on the CPU OC is currently limited to my RAM not being stable at any faster than I have it now. With my motherboard the best I can do with RAM timings is System Memory Multiplier is set at 2.50.

Questions:

Will I (likely) be able to push my RAM to higher, stable speeds if I run 2 DIMMS only (i.e. remove the 2 1GB DIMMS)?

What would the real world impact of performance be by dropping from 6 to 4 GB?

 

[Jimzz]

Usually more ram sticks means lower speeds and timings. I always try to stay with only 2 sticks in my system.

Ram is easy to pull and install so i would pull the 2 1gb and try it.

 

[Charles Kozierok]

Will I (likely) be able to push my RAM to higher, stable speeds if I run 2 DIMMS only (i.e. remove the 2 1GB DIMMS)?

Not an overclocker, but my guess is that 2 DIMMs will allow you to run at higher speeds, because fewer DIMMs means less loading on the channels.

What would the real world impact of performance be by dropping from 6 to 4 GB?

Probably greater than any benefit you're going to get from a slightly improved RAM overclock.

 

[Idontcare]

DDR2 Overvolt: +0.40 (2.2v)
- gMCH: +0.125v

Ouch, that's already pretty high for a DDR2 over-volt. Are you actively cooling those dimms with some zip-tied fans or anything like that? If not, consider it. Your dimms will thank you (and may run faster at the same voltage too).

Questions:

Will I (likely) be able to push my RAM to higher, stable speeds if I run 2 DIMMS only (i.e. remove the 2 1GB DIMMS)?

What would the real world impact of performance be by dropping from 6 to 4 GB?

Yes, more than likely. The other thing to try is loosening the timings.

But I have to ask - why are you concerned with getting more ram bandwidth? It won't really do much for you outside of improving benchmarks in synthetic tests.

Here are some tests I did with a QX6700 at 4GHz - basically the extreme example of a cpu that is going to be "data starved" by slow ram if there was ever going to be one (for the same gen processor you have):

Note there are 3 test cases here - evaluating the benefit of increasing ram bandwidth as well as the benefit of increasing the FSB (all while keeping everything else the same, including CPU clockspeed).

We see that the synthetic benchmarks give sizable increases for the increased ram bandwidth (4.2% benchmark increase on average for a 20% increase in ram bandwidth) but the improvement in real-world apps was observed to be negligible (<1%).

Even when combining a 20% FSB increase (333->400) and a 20% DDR2 bandwidth increase (667->800), the synthetic apps show a nice 8.3% increase whereas the real-world apps come in with a paltry ~1.2% increase in performance :\

Is it really worth the extra heat and degradation on your ram/NB/mobo just to get a few extra percentage improvement in synthetic benches but no tangible benefits in real-world apps?

 

[TylerS]

Ouch, that's already pretty high for a DDR2 over-volt. Are you actively cooling those dimms with some zip-tied fans or anything like that? If not, consider it. Your dimms will thank you (and may run faster at the same voltage too).

But I have to ask - why are you concerned with getting more ram bandwidth? It won't really do much for you outside of improving benchmarks in synthetic tests.

Is it really worth the extra heat and degradation on your ram/NB/mobo just to get a few extra percentage improvement in synthetic benches but no tangible benefits in real-world apps?

Wow! That's a pretty comprehensive response. Thank you.

To answer the above (and get a bit more feedback):

I am not actively cooling my RAM. I actually didn’t think I was pushing too much through them, and I have been running these RAM settings for probably close to three years now. To be honest I just threw a bit more juice at them as an easy (read: lazy) attempt at stability. I know I need to up the volts on these dimms (Patriot) to get them to work at all (Patriot support helped when I initially built this computer 5ish years ago.)

What is a “safe” over-volt? I know this is subjective, but I would love an opinion.

I am looking to get more RAM bandwidth simply because I want to push my CPU to its max. I recently installed a new Thermaltake Water 2.0 Performer and it has given me extra thermal headroom. I am pretty sure I have some room to push farther than the 3.93 GHz I am running now. I want to see how far I can get it and would love to have it over 4. I'm not really concerned about longevity as I hope to replace the core of this system with Haswell when it comes out.

The problem is: a) I am pretty sure my RAM will not stay stable any faster than I have it now, and b) my motherboard will not allow 1:1 ram (seems silly, but as far as I can find it is true) and so the best I can do is what I have (see above).

Any thoughts on this problem?

It seems to me that I am probably beating my head against the wall for very little gain. In fact, though I can get stress tests to run stable, I do seem to be running into quirky stability issues of random reboots and sluggish response – though they are happening when I’m not at the computer so I can’t even trouble shoot it well.

Maybe I am actually better off easing everything back a touch.

 

[Idontcare]

What is a “safe” over-volt? I know this is subjective, but I would love an opinion.

My mushkin redline ddr2 dimms (spendy high-quality stuff) died with 2.3V while being actively cooled.

One big issue, as I came to learn thanks to mushkin support techs, was that mobo's of that era tended to over-volt above and beyond the reported Vdimm set-point because the mobo makers were tired of people buying cheap/sub-standard 1.8V DDR2 sticks and then blaming the reboots and system hangs on the mobo.

So a 1.8V setting would actually be 1.9V and so on, mobo makers reduced their RMA claims and no one but the OC'ers suffered for it. But setting you ram to 2.2V likely means it is running crazy hot as well as likely operating at something closer to 2.3V.

The chips may be able to take it just fine, but you are not likely gaining much benefit from the OC, so in that sense it probably is just a waste of time and effort on your part to optimize something which is already well past the point of diminishing returns.

I am looking to get more RAM bandwidth simply because I want to push my CPU to its max. I recently installed a new Thermaltake Water 2.0 Performer and it has given me extra thermal headroom. I am pretty sure I have some room to push farther than the 3.93 GHz I am running now. I want to see how far I can get it and would love to have it over 4. I'm not really concerned about longevity as I hope to replace the core of this system with Haswell when it comes out.

That makes sense. Zip-tie a fan or two to your dimms so they are getting lots of aditional air-cooling, do the same to your mobo's northbridge. You'd be surprised how much instability comes from passively or poorly cooled chips on the mobo that get too hot when OC'ing.