Overclocking Sandy Bridge-E with 32GB RAM: 8x4GB or 4x8GB?

[cynan]

This should be an easy one for you platfrom gurus out there. Basically, I am wondering if I will have better overclocking bang for my buck on the X79 platform in general with 32GB ram if using 8x4GB DIMMS vs 4x8GB DIMMs?

Pros for 8x4GB: 8GB modules cost a premium to 4GB ones. Furthermore, the tighter timings and higher clock speeds seem to be harder to achieve with larger DIMMs, and therefore cost an even greater premium if even available.

Pros for 4x8GB: On the flip side, is it not easier on the CPU memory controller to only see 4 DIMMs (vs 8 ) and therefore would I not likely achieve higher clocks (albeit at the cost of lower FSB or equivalent)? Due to the quad channel memory interface, there does not seem to be much benefit in going with DDR3 faster than 1600mhz (PC3-12800)in real world applications and most benchmarks, so worrying about finding affordable high-speed 8GB DIMMs may not be such an issue (though 4GB DIMMs are still a bit cheaper, even those rated at somewhat higher speeds). Are timings (ie, CAS 9 vs CAS 10) also not worth worrying too much about? 8GB DIMMs also allow to upgrade to 64GB in future if going with an 8-module board - but I don't see that ever happening. The only reason I'm considering 32GB over 16GB is so that I can play around a bit with ram disk configs. And if I go with 8GB DIMMs, I can always save a few bucks up front by going with a cheaper 4 module board.

So, as a rule, do I go with 32 GB on X79, should I go 4x8GB or 8GBx4 to get the most overclockable/stable system?

BTW, I'm thinking of either going with an Asrock X79 Extreme4 (4 slots) or Extreme6 (8 slots), as these seem to be great overclocking boards and have a pretty decent feature set for the money. At least in the US. In Canada, for some reason, Asrock is just as expensive as Asus (as much as 50% more for the same board in Canada as in the US). This is bizarre as the price difference between countries for most computer components is negligible, but I digress...

[Saber Cherry]

For what it's worth, I have 4x8 GB up and running stably at 1866 on Intel's motherboard... but it was sold as a 4x8 1866 kit, so nothing is overclocked. It was a pain to get it up and running, though, since Intel's bios (at the time) did not correctly support XMP profiles. Make sure you get a motherboard that does! Setting the 30-odd memory subtimings manually is really confusing.

One problem is that it's hard to find high-speed 4x8 GB kits, and the ones out there are really expensive (mine cost $400). 4x4 GB kits (and 2x8GB kits) are easier to find at higher speed, but they are not guaranteed to work even at stated speed when you use two kits together. CAS latency does not seem to be very important compared to frequency on this platform, according to Xbit.

So I can't fully answer your question, but I suspect if you are buying high-speed modules you will get the best price from 4GB modules, even though you'll need 8 slots. I would not suggest 8 modules for overclocking, though.

For $600, you can get a 4x8 2400 MHz kit... :)