Memory timings and CPU overclocking?

[Rocketdog2112]

Does faster memory timing affect the limit on how much a CPU can be overclocked? 

Case in point: 

X58 Dell Alienware 2.0 version motherboard with the A11b BIOS running a i7-990X with 12gb DDR3 Crucial Ballistix Tactical Tracer 1600MHz 8-8-8-24 stock settings (with XMP enabled). With this combination I was able to successfully push the CPU overclock into the 4.1-4.2GHz range tested with Cinebench20.

I recently upgraded the ram to 24gb of DDR3 Corsair Vengence Pro Series 1600MHz 9-9-9-24 (with XMP enabled) The new ram booted up and loaded Windows 10 without any issues. (I did reset the BIOS to factory settings before installing the new ram). Now I struggle to achieve CPU overclock of just 3.7ghz without getting BSOD and restarts during the Cinebench test.

Currently only raising the overall BCLK number using the x26 CPU multiplier and x12 ram multiplier with the XMP profile running.

I have not tried to manually set any ram timings as I am still new to the OC world and just use the optional overclocking settings offered by the 990X.

It's got me how just changing the amount and slight timing speed of the ram is now affecting my overall OC ceiling as seen in the screen shot. I went from 8th to 11th place after the ram upgrade.

 

 

 

 

 

[VeganJoy]

memory overclocking will adversely affect your cpu overclocks as the added strain on your cpu's IMC will increase temps by a few degrees. are you hitting thermal limits in cinebench?

[Rocketdog2112]

1 minute ago, VeganJoy said:

memory overclocking will adversely affect your cpu overclocks as the added strain on your cpu's IMC will increase temps by a few degrees. are you hitting thermal limits in cinebench?

Not at all. BSOD occurs seconds after starting Cinebench.

[VeganJoy]

1 minute ago, Rocketdog2112 said:

Not at all. BSOD occurs seconds after starting Cinebench.

hmm i dunno then, i'm pretty new to ocing myself and i dont know much about older platforms. there may be something specific to your motherboard/cpu causing this

[Rocketdog2112]

1 minute ago, VeganJoy said:

hmm i dunno then, i'm pretty new to ocing myself and i dont know much about older platforms. there may be something specific to your motherboard/cpu causing this

I wonder if the difference between the XMP 1.2 and 1.3 profiles might be the issue? I thought the XMP 1.3 was backwards compatible?

[VeganJoy]

5 minutes ago, Rocketdog2112 said:

I wonder if the difference between the XMP 1.2 and 1.3 profiles might be the issue? I thought the XMP 1.3 was backwards compatible?

no clue there, but it may be worth messing with the timings yourself?

[Guest]

A good timing set on DDR3 is 9-10-9-27-36 around 1.65v if your looking to go 1933mhz to 2200mhz. Somewhere in that area any how.

 

[Rocketdog2112]

Eric Duncan, the mastermind of the Dell XPS 730X hybrid A11b bios was able to give me a solid answer about what's going on....

 

 

eduncan911

 

1 point·23 hours ago

 

They are backwards compatible, but the timings have to be supported and run at slower speeds/larger timings. And the timings on the A10/A11b bios only allow up to 12 GB sticks as 24GB sticks are too dense and need an higher setting than the BIOS can support (can't remember the name of the one setting that isn't able to raise that high).

In addition to that, ram compatibility is vastly different from one set to another set, with the same MCH and same CPUs. So I would forget any overclocking you have before and just start new to figure out the limits of your hardware.

12 GB is pushing the BIOS to its limits. While many claim everything is fine with 24GB, my tests across 3 different sets say otherwise and I would never recommend 24GB sets. So you're on your own here as I don't see how the BIOS can properly support them that large. "Runs fine at stock speeds" is not proof they run fine. Just shows the system is able to compensate for the errors, slowing down your overall bandwidth, while not not crashing.

So with all that said, the only way to not change the ram settings/bus when overclocking would be use the multiplier, not bus bclk. I know, not as optimum on these i7 generation, but there the only way to leave ran timings along. As the very definition of raising bclk means you are going to overclock all buses, including the ram bus. In that case, the best you can hope for is to lower the ram ratio to keep the ran speeds are an acceptable level.

IMO, this is fruitless - as the BIOS doesn't properly support these sizes. Also, the MCH on the CPU may not be strong enough. There's also some common voltage settings missing from the A11b bios, so you aren't able to push the 990X to its max.