Northbridge OC?

[Eureka]

What is the purpose of overclocking the northbridge? Also, how should I approach it? Right now I can't seem to push my NB past 2.2ghz to boot, and it will not stay stable in prime95 at 2200. I tried working it two ways:

FSB of 220 x 10
or FSB of 200 x 11

Both produces similar results. Setting the voltage from 1.1 to 1.4 does not help make it much more stable.

I'm not sure how to proceed from this point. Other people seem to get 2.4-2.6ghz NB speeds. I can't seem to push mine past 2ghz.

I'm running a Phenom 955 on a MA-790X-UD4P with 8gb Patriot Viper DDR2800 memory, with a Xigmatek S1283.

Also, I'm getting core temps of 45-50 idle... is that too high for the setup?

 

[ShawnD1]

It's not worth screwing with the FSB since it's not really a bottleneck to anything. Just change the CPU multiplier and be done with it.

 

[RavenGuard]

Originally posted by: Eureka
Also, I'm getting core temps of 45-50 idle... is that too high for the setup?

Yes, those are high idle temps. Just make sure you are under 60* load, the load temps are really the most important.

From what I've read, messing with anything other that the CPU's clock/multiplier won't really affect performance and it's best to leave it stock for stability.

 

[veri745]

Pushing the HT speed is really the best reason to up the NB. The HT link max freq. is limited by the NB

 

[Sylvanas]

1. The NB is perhaps the most important frequency on a Phenom CPU- almost more so than the Core speed. NB frequency reduces L3 cache latency and is especially important in memory bandwidth dependent scenarios.
2. NB can be manipulated by multipliers and it is generally easier to do it this way rather than HTT (it's called HTT not FSB) as you increase too many variables that way so it can be hard to determine what may be causing instability if it should occur.
3. Stock NB VID on a 955 is 1.1v. Make sure you are adjusting the NB VID or some BIOS's call it 'CPU-NB Voltage' and NOT the 'NB' voltage on the motherboard, this affects the 790FX chip and has nothing to do with the NB on the CPU (two different things, can get mixed up easily).
4. Most 955's get to 2.2ghz on 1.1v, you will need 1.2v-1.3v to get to around 2.6ghz. Load temps are the important thing.

 

[Rhoxed]

50C idle seems extremely high, i shoot for 55C tops on phenoms (for the 125W chips it is 61C max, and for the 95W chips it is 70-73C max specified by AMD)

as for the NB speed, try booting up at stock and using Amd Overdrive to raise HTT speed from 200+ by increments of 1-5 untill you become unstable in prime (run for 10mins a time) for that short time, try raising some voltages and try again, when you have topped out, back off by 5 and try to get that stable

**edit: make sure your ram is on a lower divider so that is not a factor while Overclocking the HTT reference clock

 

[Eureka]

Originally posted by: Sylvanas
1. The NB is perhaps the most important frequency on a Phenom CPU- almost more so than the Core speed. NB frequency reduces L3 cache latency and is especially important in memory bandwidth dependent scenarios.
2. NB can be manipulated by multipliers and it is generally easier to do it this way rather than HTT (it's called HTT not FSB) as you increase too many variables that way so it can be hard to determine what may be causing instability if it should occur.
3. Stock NB VID on a 955 is 1.1v. Make sure you are adjusting the NB VID or some BIOS's call it 'CPU-NB Voltage' and NOT the 'NB' voltage on the motherboard, this affects the 790FX chip and has nothing to do with the NB on the CPU (two different things, can get mixed up easily).
4. Most 955's get to 2.2ghz on 1.1v, you will need 1.2v-1.3v to get to around 2.6ghz. Load temps are the important thing.

Thanks for all the replies. Sylvanas hit the nail on the head, I've been using 'NB VID' instead of 'CPU-NB VID'. Last night I was able to boot successfully with a 2.4ghz NB speed, but I didn't have time to actually try it out. I'll start playing with the settings after work.

Is there a benefit to raising the HTT speed rather than upping the NB mutliplier? Also, on my system the HTT clock is set to be a multiple of the "FSB" setting, what is the significance of this?

I'm also going to try to reseat the heatsink this time, I've had issues before with the S1283 being offcenter. Either that or I need to redo the TIM.

 

[Sylvanas]

Originally posted by: Eureka

Originally posted by: Sylvanas
1. The NB is perhaps the most important frequency on a Phenom CPU- almost more so than the Core speed. NB frequency reduces L3 cache latency and is especially important in memory bandwidth dependent scenarios.
2. NB can be manipulated by multipliers and it is generally easier to do it this way rather than HTT (it's called HTT not FSB) as you increase too many variables that way so it can be hard to determine what may be causing instability if it should occur.
3. Stock NB VID on a 955 is 1.1v. Make sure you are adjusting the NB VID or some BIOS's call it 'CPU-NB Voltage' and NOT the 'NB' voltage on the motherboard, this affects the 790FX chip and has nothing to do with the NB on the CPU (two different things, can get mixed up easily).
4. Most 955's get to 2.2ghz on 1.1v, you will need 1.2v-1.3v to get to around 2.6ghz. Load temps are the important thing.

Thanks for all the replies. Sylvanas hit the nail on the head, I've been using 'NB VID' instead of 'CPU-NB VID'. Last night I was able to boot successfully with a 2.4ghz NB speed, but I didn't have time to actually try it out. I'll start playing with the settings after work.

Is there a benefit to raising the HTT speed rather than upping the NB mutliplier? Also, on my system the HTT clock is set to be a multiple of the "FSB" setting, what is the significance of this?

I'm also going to try to reseat the heatsink this time, I've had issues before with the S1283 being offcenter. Either that or I need to redo the TIM.

Glad to see it worked, I made the same mistake when I first got my 955- I was adjusting the wrong voltage. HTT is what programs like CPU-Z call the 'FSB' which is just for convenience sake as it's not really a Front Side Bus as per what Intel have been using for all these years- it's very different. So essentially FSB=HTT, same thing it's just what the software calls it. Why I say that adjusting the multipliers is better than HTT for overclocking is because with the multipliers you have may more control. With the HTT it comes stock at 200mhz, now for arguments sake let's say we up that to 230mhz. So now we have:

230 x 16 = 3680mhz Core Speed
230 x 10 = 2.3GHZ NB speed
230 x 10 = 2.3ghz HT frequency
2 (230 x 2) = 920mhz Memory frequency with the stock 1:2 divider.

That's 4 settings that have all been increased with the HTT. Now if something goes wrong, and we get instability- it could be any one of those settings that is the problem but we wouldn't know which one unless we changed the multipliers on each one and test individually which can take ages and even then, your results are not really indicative as a multiplier will reduce said frequency by 230mhz, which may be more than is required. So you are losing potential performance if you only need to drop down in reality by 10mhz for stability. Instead I propose adjusting each multiplier individually so what you'd end up with is something like this at stock and a little bump on the core speed only:

200 x 18 = 3600mhz Core speed
200 x 10 = 2ghz NB
200 x 10 = 2GHZ HT
2 (200x2) = 800mhz memory @ 1:2 divider.

So if anything is unstable you know for sure instantly that it is the Core that is unstable at that speed so you need only adjust that or apply a little more Vcore. So you can do this for CPU, NB, Memory and HT individually which will give you better results and the facts quicker than if you were to do it by HTT. Once you have the facts, you can tweak it later with perhaps a few mhz on the HTT.

 

[Eureka]

Thanks for the detailed reply! You have a very good point, multipliers definitely seems like an easier way to approach things.

Now, as another question what is the HT speed? I know that its a direct multiple of the HTT but what does it do? Also, do you have any reviews or information on the NB and why it is so important to the Phenom (benchmarks on core speed OC vs. NB OC)?

 

[heyheybooboo]

Originally posted by: Eureka
Thanks for the detailed reply! You have a very good point, multipliers definitely seems like an easier way to approach things.

Now, as another question what is the HT speed? I know that its a direct multiple of the HTT but what does it do? Also, do you have any reviews or information on the NB and why it is so important to the Phenom (benchmarks on core speed OC vs. NB OC)?

With the Phenom arch for each 10% increase in the IMC/NB speed memory bandwidth increases 3-4% and latency improves 3-4%. This phenomena has been tracked over at XS since the release of the original 9600BE.

And as the CPU clockspeed increases the level of improvement from increasing the IMC/NB speed (in memory bandwidth and latency) also rises. Did that make sense?

Here is a chart from Anand in Far Cry with the 720BE.

 

[Eureka]

Originally posted by: heyheybooboo

Originally posted by: Eureka
Thanks for the detailed reply! You have a very good point, multipliers definitely seems like an easier way to approach things.

Now, as another question what is the HT speed? I know that its a direct multiple of the HTT but what does it do? Also, do you have any reviews or information on the NB and why it is so important to the Phenom (benchmarks on core speed OC vs. NB OC)?

With the Phenom arch for each 10% increase in the IMC/NB speed memory bandwidth increases 3-4% and latency improves 3-4%. This phenomena has been tracked over at XS since the release of the original 9600BE.

And as the CPU clockspeed increases the level of improvement from increasing the IMC/NB speed (in memory bandwidth and latency) also rises. Did that make sense?

Here is a chart from Anand in Far Cry with the 720BE.

Thank you that made sense to me. Once I get out of work I gotta get back to playing around with this chip. 😀