Phenom II overclock advice please

[WildW]

For some Easter entertainment I upgraded from cheapy old Core2 system to a Phenom II 965 Black and set to work seeing what overclock I could manage. System is now as follows:


Phenom II 965BE - I believe it's a C3 (125W), that's what CPUZ thinks anyway.
Xigmatek Dark Knight cooler
Asus M4A77D (AMD 770) motherboard
6GB DDR2 (2x4GB Mushkin DDR2-1000, 2x1GB Geil DDR2-800 - the latter I had laying around so threw it in too - all running at 800MHz for now)
XFX Radeon 5850
PSU is a Hiper Type M 630W - in my mind its a sturdy unit from a brand I've used for a long time without issue, but I don't hear much praise for Hiper these days either so I figure they're somewhat unloved.


This is my first time overclocking a Phenom II - most of my recent experience is with Core2Duos, used to overclock AM2 Athlon64 X2's though. . .but my, things have changed a bit. Seems there are far more things to tweak these days. No longer just "FSB" and multiplier, there's now CPU Northbridge and HT link speed to confuse me. . . . and its not just "keep it under 1000MHz" any more.

So far I've been leaving most things on auto and just tweaking the CPU multiplier and VCore to get a feel for things. I tried tinkering with upping the FSB a few points and dropping the multiplier, but it seemed to make things unstable quite quickly, and my ram is refusing to overclock when I up the FSB. . . which is odd. 205MHz FSB and the ram's still sitting at 800MHz - there must be some kind of lock in there I haven't found how to turn off.



Man, this is getting long already. I'll cut to the chase. So far I've got to 200x19 = 3800MHz, but to get this stable I've had to up the VCore to 1.475V. Temperatures are maxing out at 49/50C after extended stressing. This VCore seems a bit high when I see some folks talking about 3.8GHz at stock volts.

I think the issue is Vdroopage. At first I thought I was stable at 1.45V - it ran for 8hours Prime95 small FFT without issue. It crashed out of Prime95 in-place-FFT though (maximum CPU power draw) within a couple of minutes. During in-place-FFT VCore was drooping down to below 1.4 volts, and occasionally dipping below 1.3v.

A bios update seemed to smooth out the VCore a bit . . . I plotted graphs but I don't have them to hand at the moment. The droop was only occasionally dropping below 1.4v now, but dropping VCore to 1.46V in the bios caused a bluescreen during prime, so it obviously wasn't much improved. Monitored the 12V rail during prime too, and it's stuck rigidly at 12.6V - yes, this PSU is renowned for keeping a high-but-just-within-spec 12V rail, so I don't think the PSU is necessarily the problem.


So here I am. . . I'd love to go faster and/or cooler, but not sure where to go from here. Don't know if the PSU or motherboard (more likely?) is the cause of the Vdroop, and how much is normal with one of these chips. What would you more experienced folks look at next?

 

[richierich1212]

Your vcore is high for 3.8GHz. Check if there's an option for cpu-nb voltage, and that should be around 1.2v to 1.25v. What's your NB running at?

 

[WildW]

Your vcore is high for 3.8GHz. Check if there's an option for cpu-nb voltage, and that should be around 1.2v to 1.25v. What's your NB running at?

So far those are at Auto. CPU-NB voltage is an option - the board seems to have plenty of options to tweak as far as overclocking goes - I did try raising this a bit but wasn't sure I saw any difference. At the moment I'm a bit overwhelmed with new settings to tweak that I haven't seen before, and I'm not sure where to start. The few guides I've looked at seem vague on a lot of these settings.

I did some reading around and saw people advocating NB running at 2400MHz or so, and HT-Link at the same or less. I tried NB at 2400 and HT-link at 2200 for a while, but things seemed more stable when I dropped them back to auto. Auto seems to set these to 2000MHz according to CPUZ.

Did I read somewhere that you should increase these values as you increase CPU multiplier?


The other thing of note is that I did have Cool & Quiet and C1E disabled while tinkering. I have since put Cool & Quiet back on for the time being, and it's working without issue - it'll go off again if/when I start to mess with it again.

 

[richierich1212]

Well you should get away from auto settings.

 

[WildW]

I think my plan is going to be to go back to basics, stock clocks, go down to 2 sticks of ram, and try upping things one step at a time. I shall also read up on and play with load line calibration, since I'm having Vdroop concerns.

 

[SlowSpyder]

Does your BIOS have a NB/L3 multiplier? I would keep the HT speed at 2000MHz/Auto and just adjust the NB/L3 multiplier if you can.

 

[WildW]

Does your BIOS have a NB/L3 multiplier? I would keep the HT speed at 2000MHz/Auto and just adjust the NB/L3 multiplier if you can.

I believe so - it has separate NB and HT controls, although they're described in absolute MHz terms (e.g. 2000, 2200, 2400, etc) - I believe this is actually just a multiplier and the values are the resultant speed assuming a 200MHz FSB.

 

[BD231]

1.) For your CPU-NB to run at 240mhz you'll need around 1.3v or so going to it
2.) Getting prime stable at 3.8ghz is going to be a challenge

If your voltage's are right, there aren't many programs out there that are going to crash your computer. Stability testing is where I find the Phenom II falls short. I can get seemingly any game/app stable at 3.8ghz, but stress testing will cause endless issue's at those speeds.

Most people can't put a Phenom II under that kind of load at those speeds and NOT find an issue with a stress test program. The thing is, most people who overclock are gaming/encoding/browsing the web or doing other things that don't require even 20 to 30% of the CPU's attention. For the life of me I can't find any interactive apps that put modern CPU's at full load.

Case in short, don't pull your hair out trying to get stable; it's really not worth it. Just find your max on the north bridge and your max on the cpu itself then use the apps you'd be using every day to judge whether or not the computer is stable enough for YOU.

Me personally, I got as stable as I could in prime (found the voltage's my CPU could run that program longest), which resulted in every real world app I use being stable. 240 to 250 should be easy on the northbridge, 3.7 to 3.8 should be max on the core (maybe 3.9 on that C3 stepping).

Some would say you might have to worry about errors but being that I personally only start seeing those errors after about 15 minutes into prime at 100% load it's quite clear that issue would not apply to someone who doesn't use an app that replicates the load of prime.

I've been at 100% load for days, encoding at 3.8ghz and the computer was stable because the memory bus was not being taxed in any way. If you want stress test stable you'll need to drop back down to 3.4 to 3.6ghz.

 

[schenley101]

i usually just use AMD overdrive with my phenom2 955. Its much easier and you don't have to reboot to change settings. I actually get higher overclocks with it which is sort of weird but im not complaining. I have a c2 stepping and on stock i get to about 3.7GHZ. even if i up the voltage i still hit a wall before 3.8 no matter what i do. you best bet for performance is to lower the multiplier on the core and ht link( so the HT speed stays around 2ghz) and raise the reference clock for a faster L3.

 

[WildW]

Thanks for the comments folks.

I had another play around with it last night. Load line calibration on my board is a huge tweakable spectrum, and I was easily able to eliminate Vdrooping entirely. Unfortunately it was replaced with occasional voltage spikes in Vcore, but it never dropped down any significant amount below the set value.

Unfortunately this didn't remotely help in getting a higher overclock. Prime at 4GHz still bluescreens basically instantaneously at a now believable and even hotter than before 1.45V. I don't want to go any higher, having seen the spikes in VCore of up to 0.1V that would make me nervous.

I figure it's not worth stressing over too much. My 3.8GHz quad with Cool&Quiet working is a good enough proposition for me compared to shooting for 3.9GHz without it. Everything runs awesome anyway.