Hello. I've been using an AMD Phenom x3 8450 for some years now and stumbled into one issue with it. Under the heavy load CPU Core Multipliers go from x10.5 (default value) to x5.3 which results CPU Cores frequency to jump from 2.1ghz to 1Ghz. This is really annoying when I play games because every time this happens (and it happens like once per few minutes) I have sudden FPS drop from, for example, 45fps to 15fps.
This "underclock" goes for ~5seconds and then frequencies are back to normal.
I thought it was overheating but the temps are ok I think?
CPU temp under stress testing is 50-52C max. Critical temperature for my PC starts from 60C (or 65) so this underclock starts too early, isn't it?

Cool'N'Quiet disabled in BIOS, Power Plan in Windows - High Performance.
CPU - AMD Phenom x3 8450
MB - Asus M2N-CM DVI
PSU - Chieftec A85 CTB-500S 500W

Here's a graph from Argus Monitor when the AIDA64 stress test is active as an example of those drops:



Any suggestions what to do? I'm desperate...

Call me crazy, but I'd blame the old Nvidia chipset mobo.
Are you using the latest BIOS i.e. 0501? http://www.asus.com/Motherboar...2Plus/M2NCM_DVI/#CPUS
Even it is over 3 years old.

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Spider: Phenom II 955, Antec Kuhler 920, GA-MA790FX-DS5 (F8g), ASUS 5870/V2, ASUS Xonar D2X pcie,
OCZ2N1066SR2GK (4x1gig @800), Antec Truepower New 750, Fractal Design's Arc Midi Case.
#2: A64 X2 4200+, ASUS A8V-D, SAPPHIRE AGP 1950PRO