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First off let me start by saying I've built several PC's in my time, however the last one I built was in 2007 / 2008. I'm trying to figure out if my new CPU of choice, i7-4471, will prevent me from using RAM that's spec'd for 1866Mhz / 2133Mhz / 2400Mhz at those higher rates.

I'm curious because of the Anandtech Memory Scaling on Haswell article which cites the benefits of faster RAM if you can afford it and its correlation to performance. Are RAM and CPU clocks separate or are they tied to a common clock?

Any and all help is appreciated!

Thanks in advance.

The base clock speed is tied to BCLCK. It is not locked on Sandy Bridge, Ivy Bridge and Haswell systems, so if you overclock the BCLCK. You will end-up overclocking PCI, memory, PCIe buses as well as HT Link.

You can increase memory bus speed without overclocking by changing the CPU/memory multiplier. In most cases, it is best stick with a 1 to 1 ratio.

Wow, that article specifically says stay away from 1600 MHz and below. Looking over TRs system guides, they regularly suggest 1600Mhz ram. (my guess is cost effective.

tanker27 wrote:

Wow, that article specifically says stay away from 1600 MHz and below. Looking over TRs system guides, they regularly suggest 1600Mhz ram. (my guess is cost effective.

The main recommendations from the TR system guides do not have BCLK overclocking in mind. If you have a K processor and overclock by multiplier, I don't think you need to bump the RAM speed at all?

Ahh so this so if you dont mess with BCLK it should be fine.

Krogoth wrote:

The base clock speed is tied to BCLCK. It is not locked on Sandy Bridge, Ivy Bridge and Haswell systems, so if you overclock the BCLCK. You will end-up overclocking PCI, memory, PCIe buses as well as HT Link.

You can increase memory bus speed without overclocking by changing the CPU/memory multiplier. In most cases, it is best stick with a 1 to 1 ratio.

Thanks Krogoth for the input. So if I'm not misreading what you said, I can take a locked CPU (non-K) and overclock the RAM by messing with the CPU/memory multiplier. I'd really like to know what those are now, so I can purchase the appropriate spec'd RAM. I'd hate to buy 2133Mhz only to find out (based on the multiplier) that it can't handle the given multiplier and I would be better off having purchased 2400Mhz RAM.

Flying Fox wrote:

tanker27 wrote:

Wow, that article specifically says stay away from 1600 MHz and below. Looking over TRs system guides, they regularly suggest 1600Mhz ram. (my guess is cost effective.

The main recommendations from the TR system guides do not have BCLK overclocking in mind. If you have a K processor and overclock by multiplier, I don't think you need to bump the RAM speed at all?

I couldn't agree more and considering the actual real world benefit of trying to o/c the ram with the cpu, its just not worth it considering what I am able to get out of my 2500k without touching the BCLK, 4.9 and I am sure I have a good one and could go higher but really no point.

That depends on the motherboard and BIOS settings. Most enthusiast tier boards come with 1:1, 1:2, 2:3, 3:4, 5:6 multiplier/divider ratios (CPU/Memory) and BCLCK is the base speed and DDR3 is quad-pumped so a 1:2 effectively be 100Mhz/200Mhzx4 = 800Mhz for memory speed. The more overclocking friendly boards come with a ton of options for memory multiplier/divider. To get 2400Mhz memory speed on a Z87 board will require a multiplier of 1:6 . 100Mhz for BCLCK, 600Mhz x4 = 2400Mhz memory clock.