Haswell overclocking- 2 Dimms vs 4?

[PaulieG]

So, I bought a set of 2x4GB Gskill Trident 2400's for my new Haswell build. I've now decided that I'd like to grab another set for 16GB. I know on past generations of Intel processors, filling all 4 Dimms had a significant impact on the IMC, limiting the ability to overclock to varying degrees. Since I've been out of the loop for a couple of years, I'm wondering how this all works with Haswell. How much does filling all 4 Dimms affect overclocking the CPU and memory on this platform? Can most of it's affects be counteracted by voltage adjustments?

 

[Kursah]

I have used 2 and 4 dimms and OC'd my Haswell chips just fine, since I wasn't pushing extreme limits (4.5GHz on 4770K for instance), I didn't need to adjust anything extra. There are some IO voltages you can adjust, and @cadaveca is kind of the TPU guru on Haswell tuning and OC-ing. Check out the Haswell Club Thread. Lots of excellent information!

 

[cadaveca]

So, I bought a set of 2x4GB Gskill Trident 2400's for my new Haswell build. I've now decided that I'd like to grab another set for 16GB. I know on past generations of Intel processors, filling all 4 Dimms had a significant impact on the IMC, limiting the ability to overclock to varying degrees. Since I've been out of the loop for a couple of years, I'm wondering how this all works with Haswell. How much does filling all 4 Dimms affect overclocking the CPU and memory on this platform? Can most of it's affects be counteracted by voltage adjustments?

That's the telling factor, 4 DIMMs, for me, with some CPUs struggling pushing 2400 MHz. However, the maximum multiplier available on Haswell is 2933 MHz, with a fair number of CPUs not even capable of booting that speed. 2400 MHz with all DIMMS populated is no problem for a CPU that can boot and run 2933, however, the breaking point for me with 4 DIMMS is 2666 MHz. That said, there aren't many "worthwhile" kits over 2400 MHz out there. Many of the kits out now are single-sided, and performance is greatly impacted over 2400 MHz with these sticks, seemingly due to how the memory controller works.

 

[PaulieG]

That's the telling factor, 4 DIMMs, for me, with some CPUs struggling pushing 2400 MHz. However, the maximum multiplier available on Haswell is 2933 MHz, with a fair number of CPUs not even capable of booting that speed. 2400 MHz with all DIMMS populated is no problem for a CPU that can boot and run 2933, however, the breaking point for me with 4 DIMMS is 2666 MHz. That said, there aren't many "worthwhile" kits over 2400 MHz out there. Many of the kits out now are single-sided, and performance is greatly impacted over 2400 MHz with these sticks, seemingly due to how the memory controller works.

Thanks. I've pushed these Tridents to 2606 so far, with just 2 sticks. I just wanted some idea what kind of behavior to expect once I start filling all 4 dimms.

I have used 2 and 4 dimms and OC'd my Haswell chips just fine, since I wasn't pushing extreme limits (4.5GHz on 4770K for instance), I didn't need to adjust anything extra. There are some IO voltages you can adjust, and @cadaveca is kind of the TPU guru on Haswell tuning and OC-ing. Check out the Haswell Club Thread. Lots of excellent information!

I've spent a couple of hours over there. I'm realizing that things haven't really changed all that much since Sandy Bridge, other than Haswell is toasty, so there is a bit less headroom without at least custom water. I'm going to spend some time with this Gigabyte board, getting to know more of the obscure fine tuning settings.

 

[cadaveca]

Most likely you'll need some sort of VCCSA boost (depending on voltage already used), and maybe a very minor vCPU boost. That's all. If that doesn't work, not much else will, assuming you get sticks of the same type. Even so, G.Skill won't cover issues under warranty, since their recommendation is to buy a 40stick kit, not mix separate kits. The reasoning for why they say this is just science, but they might help out a user, too, if you do have issues. I don't foresee that you would, but it's possible.

 

[PaulieG]

What's weird on my UD5H Black, is that you cannot manually type in the system agent voltage. You have to use the +/- keys to adjust it, and it starts through the negatives, so you have to scroll the negatives before increasing for some ridiculous reason.

 

[cadaveca]

What's weird on my UD5H Black, is that you cannot manually type in the system agent voltage. You have to use the +/- keys to adjust it, and it starts through the negatives, so you have to scroll the negatives before increasing for some ridiculous reason.

ASUS is still the leader for user-friendly BIOSes, but other companies like MSI are slowly catching up with their own take on how a BOIS should operate.

I am not too fond of Gigabyte's new BIOS design myself, but thankfully you can revert to the old-style blue BIOS screens with a single button press.