Hi,This motherboard has known throttling issues, even at stock speeds!
I have the ASUS M5A78L-M/USB3 motherboard with an AMD FX-4100 3.6 GHz running at stock speeds and an Arctic Freezer 13 Pro tower heatsink cooler (with cross-blow fan) plus two 120mm top case fans beside the CPU heatsink. Full system specifications in my signature.Even at stock speeds
, when stress testing my processor with IBT or OCCT at 100% load, my FX-4100 will constantly throttle down
from 3.6 GHz stock to around 3.3 Ghz then back up again, with the multiplier constantly jumping back and forth between 18 and 16.5.
This is with Turbo Core, C6 and Cool 'n' Quiet disabled in the BIOS and power settings in Windows set to High Performance settings. It is not possible to disable C1E or APM in the BIOS of this motherboard, however. I have flashed my ASUS M5A78L-M/USB3 motherboard to the latest BIOS version 1503 (2012-12-04). I have also tried undervolting down from 1.41 V to 1.35 V and even 1.25 V respectively.
I have verified the throttling issue not to be attributable to high system temperatures during full load as they were only hitting around 25°C max on the CPU and 35°C max elsewhere on the motherboard. My AMD FX-4100 idles at a very cool 5°C thanks to the Arctic Freezer 13 Pro cooler.
Evidently, APM keeps kicking in and throttling down my CPU to prevent overheating and damage to on-board components such as the VRMs.Touching the VRMs beside the CPU socket, they get very toasty indeed during 100% load. This has been widely experienced and reported by many other owners of the same motherboard series, both at stock and overclocked speeds.
To confirm whether this is the case, since it's not possible to disable APM in the BIOS, I used the AMD Overdrive program to disable AMD Turbo Core, which as documented in AMD's official 'AMD FX Performance Tuning Guide' on p10, also disables APM. With APM disabled I ran another stress test with IBT and also OCCT, and at 100% load the multiplier remains at 18 and core speed at 3.6 GHz, thus indicating that APM and overworked VRMs to be the culprit.
This means that, in order for me to be able to run my AMD FX-4100 even at 3.6 GHz stock speed on this motherboard during 100% load, I have to circumvent APM using AMD Overdrive. Of course, circumventing APM and the throttling is not a good thing since it's throttling for a reason!
The ASUS M5A78L-M/USB3 specifications
states CPU support for up to 140W - yes in the sense that the processor will work, but for the majority, not as you'd expect.Edited by alvinc5 - 3/9/13 at 2:11pm