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Overclocking with the M3N78-Pro - oh boy. CPU speed drops under load :'(

post #1 of 12
Thread Starter 
So I am running an M3N78-Pro with my budget Phenom II X4 805. I decided to OC a bit as my performance in regular computing and some encoding was...lackluster. I ended up getting a moderate 230x12.5 overclock quite stable.

I left all OC settings to auto (like a boss) except CPU vcore, which is set to about 1.39v under load. I honestly miss my LGA775 overclocking but that's another day. All other CPU-spread spectrum and the rest are all disabled of course. I had a few concerns though.

Under load, vcore doesn't droop much but my CPU speed droops intensely. The CPU multiplier remains at 12.5x but the speed will drop from 2891Mhz to 100-600mhz. I have all the power-saving bits disabled in the BIOS and I also have the TLB fix patch disabled. CPU temps are well under 55c and I thought maybe the NB was overheating - which it was. According to Everest ultimate my MCP temps were about 64C under load.

So what did I do? I epoxy'd an 80mm fan to the hilariously inadequate NB heatsink. Temps under load now are about 46C. Nice.

This did not fix the issue. So my next thought is that the 4+1 phase power design is too weak for the x4 805...which also does not make sense. This is a 95W CPU and older AMD CPU's had a higher TDW and this issue would not occur with them. So what gives?

Has anyone experienced this and found either a BIOS fix or other fix to be able to alleviate the problem? I am updated to the most recent BIOS 1301 and all other drivers are up to date as well.

Thanks
Edited by d3v0 - 6/12/11 at 8:32pm

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post #2 of 12
Thread Starter 
Any thoughts fellas?
post #3 of 12
Thread Starter 
Update: changed to a Phenom II 965 and it's still dropping under load, even with the settings on auto and the frequency as stock 17x200.
post #4 of 12
It's a terrible board. You may have to go to extremes on voltage to ensure a stable OC.

Obviously don't over do it.
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post #5 of 12
mosfets overheating maybe?
ASUS boards use to have a mosfet overheating protection, which will underclock your cpu, but I dont know if your board has it
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post #6 of 12
Thread Starter 

Here's what it's doing.

I'm not sure about mosfets but there is adequate air flow in the case and reasonably low ambient temps.

With the 965 I'm using it's not even overclocked at all.
post #7 of 12
... but there is no heatsink on them
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post #8 of 12
Thread Starter 
Do you propose that I epoxy a heatsink on them?
post #9 of 12
I answered this in another thread. The board is a 3+1 phase and incapable of properly running a 125W processor, the result is thermal throttling/VRM protection (CPU speed & volts dropping during load CnQ style due to VRM overheat/overload), built into the PWM controller of most ASUS boards. You need at least a 4+1 phase to reliably run a 125W processor at load with no hiccups - well built (quality) and cooled (stock CPU cooler/airflow, or separate VRMsinks) of course.

EDIT: I noticed you're using EVEREST. Apparently during load sometimes for me, the EVEREST gadget does not correctly see the bus clock speed, making it appear downclocked, and in your case making it look as if the CPU is throttling. You can see that the CPU multi remains 17X. That might more likely be your problem. Your VRMs might actually be fine as long as you are not overclocked, since you are using the stock cooler, but I recommend push it no further than there.

EDIT 2: You have the M3N78 PRO, not the SE (like the guy in the other thread). This is a 4+1 phase. It should run that CPU w/stock cooler just fine without any VRM hiccups. So the problem is more likely indeed wrong bus clock detection by EVEREST.
Edited by xd_1771 - 6/12/11 at 10:00pm
post #10 of 12
Thread Starter 
Awesome thank you so much for the help! Everest is usually quite good so I am kind of peeved that they have this issue...but it's much better than the CPU throttling
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