Phenom II 955BE and the NB

[SpamShadow]

I just have a general question that I can't seem to get a good answer on. Is overclocking the NB worth the time and temps? I've read on a few forums that OCing your NB is key to getting the real speed out of your Phenom II, while others say its entirely not worth your time.

I fiddled with it some myself. At 3.8Ghz w/NB at 2.6Ghz my third core fails P95 on the first test. At 3.6Ghz w/NB at 2.6Ghz everything runs fine. Regardless, OCing my NB seems to bring my core temps up quite a bit. So does it really make a difference? Or should I just leave it alone and keep trucking like I always have? Thanks.

 

[buzznut]

I just have a general question that I can't seem to get a good answer on. Is overclocking the NB worth the time and temps? I've read on a few forums that OCing your NB is key to getting the real speed out of your Phenom II, while others say its entirely not worth your time.

I fiddled with it some myself. At 3.8Ghz w/NB at 2.6Ghz my third core fails P95 on the first test. At 3.6Ghz w/NB at 2.6Ghz everything runs fine. Regardless, OCing my NB seems to bring my core temps up quite a bit. So does it really make a difference? Or should I just leave it alone and keep trucking like I always have? Thanks.

NB overclocking can be somewhat beneficial to overall system speeds in benchmarks, but I feel they are not really helpful in real world usage. You will have better CPU overclocks without messing with that in general.

I haven't done a great deal of NB overclocking, but I know that system stability is better if one matches the northbridge and HT speeds.

Raising core temps will hurt a CPU overclock, so in terms of your question I don't see NB overclocking as a boon, but again if you are trying to acheive the best frame rates or other benchmarking suite score then raising the NB speed is one way to squeeze just a bit more out of your system. So go for a balance of thermals, stability, and max overclock.

 

[beenthere]

I have found each CPU to be unique. Some like to have the NB stay in ratio and some do not. The links below will give you some people's experience but IME there is no set rule and as with all OC'ing it's cut and try to find what works best for your hardware. Heat seems to be the biggest controlling factor so staying at or below 55C under P95 or OCCT keeps the system stable.

http://www.overclock.net/amd-cpus/902756-amd-overclock-guide-newbs.html

http://www.overclockers.com/forums/showthread.php?t=596023

 

[ilysaml]

simply, yes it helps. This article will help you understand how it works and benefits from OCing NB
http://www.overclockers.com/the-importance-of-northbridge-overclocking-with-the-phenom-ii/

In short, you won't get that incredible performance, just more scores in a benchmark program, 10-15 FPS increase in games with a moderate OC of NB.

EDIT: This article also greatly shows the impact of NB OC on FPS with AMD Thuban scaling.
http://www.anandtech.com/show/3877/asrock-890fx-deluxe-full-review-and-an-investigation-of-thuban-performance-scaling/7

 

[buzznut]

Ok, so I just did a quick experiment. I changed my NB freq to 2400 from 2000, also my HT freq to 2400. At the same time, although I should have waited I suppose, I overclocked my ram from 1333Mhz to 1600.

One benchmark had no change at all, a simple one at pcpitstop but I can run it in less than 5 minutes.

WEI did see a nice increase however:
Original: X3 720BE at 3.6Ghz, ram 1333Mhz, OCZ Vertex 3, HD 4850, NB and HT, 2000mhz

6.7
7.4
7.3
7.3
7.9

WEI NB 2400, HT 2400, ram 1600

7.0
7.6
7.3
7.3
7.9

So a nice little bump in the CPU and ram scores. Real world it probably has no difference but nice for benching.

 

[buzznut]

I've never tried 3d mark11, but I'll check it out.

 

[SpamShadow]

Thanks for the numbers. Real world performance is what I'm concerned with, I only bench for reference. I'll probably stick with the 3.8Ghz w/o the NB OC, better temps, and from the looks of things, better performance. Thanks again!

 

[SpamShadow]

Best answer selected by SpamShadow.

 

[buzznut]

Glad to help-
I ran some tests with 3d Vantage and overclocked my video card. Eventually I placed 4th with my particular hardware, if I had a bit more time to tweak things I'm sure I could get a little better. For now I'm keeping my NB and HT at 2400Mhz.

 

[Wisecracker]

For each 10% you increase the speed of the IMC/NB, memory bandwidth is increased 3-4% and latency is reduced 3-4%. Additional improvements may be seen by tweaking your timings.

Increasing the speed of the HT link is generally worthless and adds nothing to performance -- as a matter of fact it lends instability. Keep the HT link speed in the area of 2000MHz; additional speed does not increase HT bandwidth. Hypertransport links are simply pipes that provide a level of bandwidth beyond that needed in a desktop computer.

PhII945
15x200MHz
IMC/NB & HT Link: 2000MHz
Memory Bandwidth: 11.88gbs
Latency: 87.6ns
L3 Cache: 52.6gbs

PhII945
14x250MHz
IMC/NB: 2500MHz
HT Link: 2000MHz
Memory Bandwidth: 13.79gbs
Latency: 72.5ns
L3 Cache: 63.04gbs

Substantial gains will be found in memory-intensive applications. Here is an example of improvements to your gaming in an article from Anand

Not bad for a game in which AMD is not typically seen to perform well ...

[:jaydeejohn:5]

 

[SpamShadow]

So any thoughts on why my third core always fails P95 when my processor is at 3.8 and my NB is at 2.8 (or even 2.6)?

 

[Wisecracker]

Check your NB volts. From the article ...

...All that required was a simple increase in CPU/NB VID from 1.200V to 1.375V with this particular CPU. Some CPUs will require additional voltage and/or improved cooling to clock up the Northbridge speed to this level. In our experiences to date with the Phenom II processors, all of our samples have hit 2.8GHz with 1.375V to 1.425V on good air-cooling.

I don't really go beyond 1.25v to 1.3v to get 2500-2600MHz. Serious tweakers are taking the IMC/NB past 3000MHz on newer chips. Also make sure that your RAMs are running within spec and that your HT is around 2000MHz

There is also a 'point of diminishing return' beyond 2600MHz - probably a 2% gain in bandwidth/latency reduction for each 10% increase in clock speed.