Which is better, higher bclk or higher overall frequency?

[Shurman292]

Hey guys,

 

Just the other day I had to reduce my clock speed because I was getting a little concerned with my folding temps. I went from 4.0 ghz to 3.9 ghz on an i7 930 (on air).

 

I was wondering which is faster overall, a higher bclk (200 x 19 to give 3.8ghz but faster RAM speeds) or a higher overall frequency (186 x 21 to give 3.9 ghz but slower RAM speeds).

 

Both are stable at 1.9375vcore and reach the same temperature, so does it matter which one I choose?

 

Thanks!

[Alexandre]

What is you RAM speeds for both settings? Have you tested the computer at either setting? Also what is your uncore frequency?

 

Now for your question: From what little computer architecture I have learnt - System RAM is generally slow in comparison to CPU and CPU cache RAM. Usually cache operates at a frequency very close to that of the CPU while system memory operates at a much lower frequency (RAM speeds) meaning that it takes longer to Read/Write to System memory than it does to cache. Fortunately software code is written in such a way that the next instruction or whatever memory information which the CPU needs is close to the instruction which was called previously or close to the data which was called previously. Thus by simply grabbing a large block of data (a bit after and before the current instruction/data) from System RAM and putting it into cache you are able to run software faster (in theory). You still have to access system RAM obviously but not as often thus increasing performance.

 

Given this, we know that increasing the overall CPU frequency will allow you to process things faster and access your cache faster. Having a slightly lower memory speed will increase the time it takes to obtain data from the system memory but because this memory is slow either way, it wont have as much impact on performance since cache is less affected by RAM speeds than it is by CPU frequency.

 

Disclaimer: This is all a very high level view, based on a broad understanding of general computer systems from a course I took at university. I would not be surprised if it is wrong due to differences in how certain CPU's work (maybe cache is more closely connected to the RAM speeds in the i7 930 than I think) but it does sorta help describe what is going on and why I believe it would probably be better to keep in the increased CPU frequency with slower RAM speeds than it is to have faster RAM speeds and lower CPU frequency.

 

Please correct me if I am wrong guys! I would love to learn more about computer systems

 

My 5 cents

Edited December 10, 2011 by Alexandre

[Shurman292]

Thanks for the reply, that makes a lot of sense and it's what I was thinking! I'm away from my computer right now but I think it's rated at 1530 mhz and 1440 mhz, somewhere right around there.

[Alexandre]

Thanks for the reply, that makes a lot of sense and it's what I was thinking! I'm away from my computer right now but I think it's rated at 1530 mhz and 1440 mhz, somewhere right around there.

Yeah I think that memory frequency difference will be negligible to your overall system performance.

 

Btw, in case you didn't know, I found this to be an awesome guide to overclocking bloomfield and gulftown processors (first gen 1366 pin i7's).

[Tjj226_Angel]

Thanks for the reply, that makes a lot of sense and it's what I was thinking! I'm away from my computer right now but I think it's rated at 1530 mhz and 1440 mhz, somewhere right around there.

 

It honestly depends. If it for gaming, then go with a faster processor. If you are doing video trans-coding or editing then faster ram is the way to go.

[Queenz]

Can anyone confirm if messing with the BCLK on the new Z68 boards is dangerous? Factory settings are 100. I read up on it on some other websites saying the changed the BCLK above 100 runs the risk or ruining the motherboard in the long run because your also altering the PCI-E frequency and other things when changing the BCLK because it's all tied together? Can anyone confirm if that statement is true?

Edited December 10, 2011 by Queenz

[Krieg1337]

Can anyone confirm if messing with the BCLK on the new Z68 boards is dangerous? Factory settings are 100. I read up on it on some other websites saying the changed the BCLK above 100 runs the risk or ruining the motherboard in the long run because your also altering the PCI-E frequency and other things when changing the BCLK because it's all tied together? Can anyone confirm if that statement is true?

 

It basically just doesn't work. The highest on a board was I think 105, they usually crash at the slightest increase of the BCLK. Sandy bridge is for the ones who want easy OC'ing, just up the mulitplier and make sure it stays cool.

[d6bmg]

@Alexandre: very nicely explained. The whole scenario & answer is in your post. Now its upto OP.

+1.

[Shurman292]

Thanks for the responses guys! My QPI frequency (uncore right?) is 3345mhz. 1487mhz on the ram at the lower bclk and 1550ish on the higher bclk. I wouldn't imagine it would make too much of a difference (like Tjj said, mostly between games and transcoding) but I was just curious.

[IVIYTH0S]

I used to think that higher base clock or front side bus was more important if CPU speed was similar and I think at one period in time it was more beneficial but with current architecture, I don't think it makes much if at all any difference with today's chips. It will however make overclocking harder as it's adding more stress to the motherboard and adds more resistance towards the final max overclock.

 

And when it's between added RAM speed or CPU speed, ALWAYS choose CPU speed!

[Alexandre]

... My QPI frequency (uncore right?) is 3345mhz...

Go to page 2 of the overclocking guide I gave you above. It explains what QPI and Uncore frequencies are

[medbor]

cpu speed will be better for most benchmarks, but for actual useage i have no clue.

You will get better computer-cpu bandwith, but that is usually not needed with all the cache we have today.