Overclocking Phenom II 955 BE not idling over 3.8Gh

[bdanny55]

Hello,

I've been trying to put some new life in an old PC and bought a second hand cooler off ebay to do some overclocking.

Motherboard: Asus M4A77T
CPU: Phenom II x4 955 BE
PSU: OCZ 450W

I've been overclocking with multiplier only, using "Dolk's Guide to the Phenom II" and the main problem I've run into is that when reaching 3.8Gh (multiplier at 19 HT/FSB at 200), the CPU stops cutting the multipliers when not in use, ending up with the CPU stuck at 3.8Gh even on idle. This ends up with higher temps and fan spinning more at idle.

I don't have a stable overclock yet, but I don't want to bother pushing it further without getting to the bottom of this.

And while I'm here, I'd also like to ask anyone who knows a couple more questions: whether I need to touch RAM at all if I leave FSB/HT at stock 200? And the motherboard I'm working with also has HT Link Speed and voltage separate, should I touch that or leave it on auto?


Thank you!

 

[trents]

What we often found with that generation of AMD CPUs was that using a combination of the multiplier and the fsb would allow us to get by with a little less voltage at the same overclocked frequency. But you need to realize it is a more complicate way of overclocking since you have to adjust other voltages and frequencies at the same time to achieve stability, such as the RAM frequency and the CPU/NB frequncy and voltage and the HT Link frequency. The reason being that the FSB is the master frequency of the system and these other frequencies are tied to it. When you raise the FSb all frequencies go up, not just the CPU. And all the others need to be tweaked on to prevent any of them from becoming a source of instability.

So if you want to try your hand at overclocking by the FSB, I would suggest starting by lowering the starting memory speed to the next lowest divider (e.g. if it's 1600 memory, start with it at 1333. If it's 1333, start it at 1066). Also lower the HT Link and CPU/NB multipliers by 1-2x to start with to create some headroom. Work at raising the FSB to the point where your RAM is back to it's rated speed an the HT Link is back to around stock speed. With Phenom IIs, he HT doesn't like to be overclocked much and there is no performance advantage to doing so. The CPU/NB will overclock easily to around 2500 mhz with a little extra voltage (try 1.225-1.25) and that one helps improve memory performance. After getting your RAM back to rated speed using only the FSB then you can continue to overclock the CPU cores with the multiplier, if there is anything left.

Make sure you stress test throughly to confirm you are indeed stable. And watch temps when stress testing. Those Phenom CPUs start to get unstable when core temps get around 55-60c on an overclocked CPU. Check socket temps, too which is one of the TMPIN lines in CPUID HWMonitor. Which TMPIN line will depend on the motherboard. That temp tops out at about 64-70 before instability sets in.

What cooler are you using?

 

[bdanny55]

Hey, thanks for getting back to me. I'll try that and see if the multiplier gets stuck at full. The reason I didn't touch the FSB is because of two reasons: I didn't want to have to mess with DDR timings (it's DDR3 1333) and the board I'm using doesn't have multipliers for HT and CPU/NB, instead giving freq. and I don't know how that fares.

I've also been stuck because the LLC seems backwards compared to my intel chip, and was actually reducing my voltages instead of increasing them. I turned that off and now at last I'm getting quite stable.


Again, thanks for the info.

 

[trents]

Many bioses give frequencies instead of multipliers for the CPU/NB and HT Link. It's the same thing. For instance, if the CPU/NB and HT Link area 2000 at stock that means the implied multiplier is 10 since we know the stock FSB is 200 mhz. 10x200 is 2000. So 2200 would be a multiplier of 11 and 2400 would be a multiplier of 12. It's the end result of the frequency that counts, whether you raise the frequency directly or the multiplier. So if you increase the FSB to 250 mhz and leave the HT and CPU/NB at the stock 2000 mhz then the end result would be a frequency of 2500 for both HT and CPU/NB, since at 2000 the multiplier is 10x. So to lower the HT, for instance to 2200 mhz you would move the baseline HT frequency back to 1800 mhz since at 1800 the implied multiplier is 9x (9x200 = 1800). To put it another way, lowering the HT and CPU/NB starting frequency is the same as lowering the multiplier. And raising the HT and CPU/NB is the same as raising the multiplier.

You don't have to mess with memory timings if you start your memory at a lower divider since you are working your way back up to stock memory frequency anyway when using FSB.

 

[bdanny55]

OK, thanks to you I've done just that. And I'm currently running prime blend at 250FSB 3750MhzCPU, HT at 2000, CPU-NB at 2500 and ram at 1333. The multiplier does go down now.

However something shady is going on because the cpu seems to throttle itself for about a second every 30 seconds, dropping down to 4x ratio, 1000Mhz, and then going back up. The temperature is at a constant 51C, then drops to 40C and back to 50C when the ratio jumps back up.

I think it's the NB overheating or the mosfets/VRM, I've lowered the CPU-NB voltage quite a bit now and it's still doing it. However tomorrow maybe I'll reapply the heatsink on the NB and I've got some tiny heatsinks I could slap on the hot bits. I'm not sure if this would be helpful or maybe I should just keep a lower OC since this board was quite cheap and maybe I'm expecting too much.

Thanks for your help and if you have any input on the latest issue, I'm all ears (or eyes, rather). But tomorrow, as I'm going to sleep now.

 

[trents]

I'm thinking the motherboard power phase components are pooping out. One thing we do in these situations is to position a spot fan to blow on the VRM area and even on the backside of the socket. Small fans of about 50mm work well for these spot applications. But the fact is, the motherboard is limiting you it sounds like. But also keep in mind that there is no real world app that will heat the CPU up like P95 and it is sort of an artificial test and a hedge.

You might try AIDA64 Extreme or Realtbench instead. Lot of folks are moving away from Prime95 with the newer processors with AVX2 instructions because it is such a heater. Remember, the goal to confirm stability, not to test the cooling capacity of your system. AIDA64 and Realbench both do a good job of this if your run them for a longer period of time.