CPU Speed vs. Cache Speed?

[RaistlinZ]

So I've had my 4770K up and running for 3 days now. Stable at 4.5Ghz but haven't pushed it further yet. I was wondering how important it is to have Cache speed equal to CPU speed? My Cache is running at 4.3Ghz. Will it increase instability to run the Cache at 4.5Ghz?

 

[BonzaiDuck]

So I've had my 4770K up and running for 3 days now. Stable at 4.5Ghz but haven't pushed it further yet. I was wondering how important it is to have Cache speed equal to CPU speed? My Cache is running at 4.3Ghz. Will it increase instability to run the Cache at 4.5Ghz?

I'm not familiar with Haswell. On my old SB Z68 board, I don't think I ever saw a feature for adjusting cache speed.

You would always expect the cache speed to be less than CPU. IN the hierarchy of memory and storage, cache is the second-most expensive and fastest memory -- excluding CPU registers. The purpose of cache is to buffer data from slower, less expensive RAM.

Personally, I wouldn't bother with it. Others may offer a different opinion.

 

[BallaTheFeared]

Important for squeezing out that extra few points in a benchmark.

Completely unimportant for day to day use, and it can destabilize the core or require it to use more voltage at the same clock speed.

I haven't verified it myself, but I think OCN came out with something like 800Mhz of cache = 100MHz of core.

 

[Homeles]

Important for squeezing out that extra few points in a benchmark.

Completely unimportant for day to day use, and it can destabilize the core or require it to use more voltage at the same clock speed.

I haven't verified it myself, but I think OCN came out with something like 800Mhz of cache = 100MHz of core.

To clarify, Balla is saying cache speed isn't as important as CPU speed. Raising L3 clocks will likely lead to instability, but it's definitely worth a try.

 

[BonzaiDuck]

To clarify, Balla is saying cache speed isn't as important as CPU speed. Raising L3 clocks will likely lead to instability, but it's definitely worth a try.

Just off the top of my head, and considering where cache speed ranks with CPU/registers and RAM, I'd say that cache size matters more. EDIT: That is, it matters more than cache speed, if processor speed(s) are faster.

And again -- off top of my head -- it seems like the history of Intel CPUs has followed a path with deluxe L3 cache adding as much as $500 to the second-place processor in each line. And the path has followed two directions: number or CPUs, and amount of cache. This has also been an obstacle in chips that are more and more compact, with more and more transistors to fit in a smaller space with lower power requirement and better performance.

 

[RaistlinZ]

I've put the cache at 4.5Ghz and no issue so far. I figure if the cache is slower than the CPU speed then the CPU is always waiting for information, correct?

 

[Homeles]

I've put the cache at 4.5Ghz and no issue so far. I figure if the cache is slower than the CPU speed then the CPU is always waiting for information, correct?

10+ years ago, you may be right. However today's CPUs have various buffers to keep instructions flowing when await for data/instructions from cache/memory.

Anyway, the clock you're playing with is for the L3 cache only. CPU performance isn't nearly as sensitive to the L3 clocks as it is for the L1 and L2, but you can't adjust those anyway since they're part of the core.

 

[BonzaiDuck]

10+ years ago, you may be right. However today's CPUs have various buffers to keep instructions flowing when await for data/instructions from cache/memory.

Anyway, the clock you're playing with is for the L3 cache only. CPU performance isn't nearly as sensitive to the L3 clocks as it is for the L1 and L2, but you can't adjust those anyway since they're part of the core.

That would pretty well nail it. You can't adjust the faster cache speeds, and what L3 offers is larger cache -- not faster cache.

Just on this angle per different levels of the pyramid, I've been watching prices on the Samsung EVO 840 500GB to 1TB SSD units. I'm thinking I could replace my ISRT configuration with a Patriot 64GB SSD.

My rig seems like a slug when ISRT is turned off, and seems bottleneck-free with it turned on. So I'm not sure the conversion is worth it to me this month. I'm sure I'd notice the difference, though.

 

[PliotronX]

Important for squeezing out that extra few points in a benchmark.

Completely unimportant for day to day use, and it can destabilize the core or require it to use more voltage at the same clock speed.

I haven't verified it myself, but I think OCN came out with something like 800Mhz of cache = 100MHz of core.

I'm no expert on HW by any means as I've only had mine a handful of months but that seems a pretty conservative number though I'd imagine very safe. Aligns with one advisory about keeping it around 3.8GHz. Good to keep it around there to eliminate it as the instability then tweak to your fantasy.. I mean stimulation... I mean preference.