E6600/6700 Overclocking

[Sapiens]

I've been planning on building a new system with an E6600 (or even an E6700 considering the recent price drop) and overclocking it. From the information I've seen, overclocking seems fairly straightforward -- if I wanted a 1:1 ratio with an E6600/DDR2-800 RAM I'd up the FSB to 400 and drop the multiplier from 9 to 8, achieving an 800 MHz increase.

After poking around on the web a bit I've seen several comments stating that lowering the multiplier is an ineffective way of overclocking, or that the performance gains are minimal when you decrease the multiplier. What's so bad about lowering the multiplier to achieve a 1:1 ratio? Is it really that ineffective?

 

[lopri]

It's all about the so-called 'straps'. The NB (which is also a memory controller) has its own multiplier and frequencies (kinda like CPU/memory), and in order to achieve higher FSB, NB has to loosen its internal latency, which affects the overall memory performance. What you want is the lowest strap setting + highest FSB combo. Most of times the the strap change occurs in various chipsets as below:

1. Up to 300~330 FSB: 800 strap
   Up to 400~450 FSB: 1066 strap
   Up to 400~550 FSB: 1333 strap

These are not set in stone but rather a very broad approximation. Different chipsets and different boards will employ different configuration. Normally where strap changes, you'll have a hard time booting and maintaining stability, or will notice a bandwidth drop (run Super Pi or Memtest).

 

[lopri]

So for example, if your board changes strap @425 FSB, 9x400 will probably give a better performance than 8x450 even though the CPU frequency is the same. Quad-core (at least in current form) is in somewhat different situation because the communication between each pair of cores is carried on through FSB, so often times higher FSB is preferable than tighter chipset timings.

 

[Sapiens]

Thanks for the great explanation lopri.

Do you know of any resource that would show the strap changes for various boards? I originally had my eye on a P5B Deluxe but a P35K Deluxe is looking more appealing since I think pushing the FSB to 400 would be a bit easier (moving up from 333 instead of 266, yes?). Which one of these boards would be better at overclocking an E6600 or E6700 up 800 or 1000 MHz respectively? I'm leaning towards the P35 just to be fancy, but fancy doesn't always cut it.

 

[Sapiens]

Update: With a bit of Googling it looks like both the P5B Deluxe and P5K Deluxe don't change the strap at a 400 MHz FSB, which is what I'd be shooting for anyway. Does this sound accurate?

 

[SinfulWeeper]

Woah, comes to show how long I been outta the picture. Last I built a computer was on a S478 platform where the multipliers are locked. You could not raise or lower them.

 

[five4o]

So on Gigabyte DS3 which offers better performance E6600 3.2GHZ @ 9x356 or 8x400
Did some googling but I didn't find an answer

 

[Sapiens]

Originally posted by: five4o
So on Gigabyte DS3 which offers better performance E6600 3.2GHZ @ 9x356 or 8x400
Did some googling but I didn't find an answer

"We were also able to boot and enter Windows XP at 9x408 FSB with the F6 BIOS but we had to change our memory settings to 5-6-5-18 for the system to complete the entire benchmark suite that includes eight hours of dual Prime95. The performance penalty from running the relaxed memory latencies along with the switch to the 1333 memory controller strap once we passed the 401 FSB setting resulted in performance that was up to 7% less across a wide variety of games, applications, and synthetic benchmarks. We determined our final setting of 9x385 FSB offered the best blend of performance and stability with the F6 BIOS. We also tested the F4 and F5 BIOS releases and had the same basic results."

http://www.anandtech.com/mb/showdoc.aspx?i=2854&p=2

Looks like it's 401 for the shift from 1066 to 1333 on that board.

 

[Canterwood]

Originally posted by: five4o
So on Gigabyte DS3 which offers better performance E6600 3.2GHZ @ 9x356 or 8x400
Did some googling but I didn't find an answer

On my DS3 8x400 has better performance.

 

[Sapiens]

I guess another important question that isn't completely on topic would be how easily an E6700 overclocks to 3.6 GHz. I've heard pushing an E6600 up to 3.2 GHz isn't bad at all, is the E6700 the same way? I imagine I'll be using a P180 with an NH-U12F for cooling.

 

[aigomorla]

Originally posted by: lopri
So for example, if your board changes strap @425 FSB, 9x400 will probably give a better performance than 8x450 even though the CPU frequency is the same. Quad-core (at least in current form) is in somewhat different situation because the communication between each pair of cores is carried on through FSB, so often times higher FSB is preferable than tighter chipset timings.

hmmmmm interesting post indeed lori!

i have a question for you. I have a very nasty fsb wall.

from 376->399 it wont boot worth dookie at any voltage. @ 400 it boots at 1.57V bios, which is roughtly 1.45Vcore real.

You know of anyway to get past this stupid wall? i would preferably like to run my chip at 1.42Vcore real @ 3.4ghz. *sigh*

reason why i dont just keep her at 3.6 is because of voltage. My computer is loaded 100% 24/7 WCGing. So i honestly dont like load temps in the upper 60's 24/7.

Ummm i know upper 60's is excellent, and currently she wont break mid 50's even 100% loaded. But i like things very cool. :T


Any help to pass that stupid FSB wall would be greatly apreciated. See sig for board/memory combo.

 

[lopri]

Didn't see your post, aigomorla. To tell you the truth, even before I got my Q6600 my goal was 8x400, and ever since that's achieved I didn't really bother with any other configuration except clocking a bit higher to 8x412.5 which was also not too hard (but temps were too high for my taste). I did test 9x355, which gives the same CPU frequency (3.20GHz), without a problem but noticed a lower performance than 8x400. Didn't really fiddle with FSB overclocking because I knew the quad-core OC under air-cooling is limited by temperatures. And after that my interest was all about memory. (you know, 8GB. )

I will try out 376~399 FSB on my board and report back within 24 hours.

 

[lopri]

Yup. Quick testing with my current configuration shows that I have an FSB hole just under 400 FSB. But my hole is a bit tighter than yours. ($(^@#&$)%#@$) :laugh:

Anyway, I can't boot between 375FSB~389FSB. (can boot from 390FSB and up) The board pretends to boot normally with the beep but the screen hangs at "EM64T CPU" or something like that. I can try it again with 1GB D9 sticks, but I think you're right in that there is a hole. But with quads, I can't really be sure whether the hole is because of strap changes or just plain immature BIOS. Remember when 680i first came out? With an E6600, there were about a million FSB holes that couldn't directly be attributed to strap changes. And just like it did with E6600s last year, every single board could be different in the degree of severity when it comes to FSB holes, so I guess we'll have to wait for BIOS updates.

P.S. I just found out that I can't boot @420FSB but can boot @440FSB. LOL.