Weird CPU behavior on an old motherboard, can you explain it?

[Assoul]

I have an old computer which I figured I could upgrade for a lot cheaper than buying a new one. Here are the specs:

Mobo: Asus M2N-VA
CPU: AMD Phenom II X4 965 (stock speed)

It's an AM2 motherboard with an AM3 CPU; the CPU voltage is a little bit higher than the board allows but the computer still booted (95w vs 125w). Here's the problem: it booted at 800 MHz by default. I went inside BIOS and tried tinkering with the multiplier and voltage and managed to get it to 3.5 GHz stable, but while Windows confirmed that this is the correct clock speed, everything was super slow. I ended up downloading a program call Phenom MSR Tweaker and managed to get it to 3.5 GHz and my Passmark scores were slightly less than what's posted on the Passmark website, games run properly, etc.

Is there a reason why I have to use the Phenom MSR Tweaker? It's almost like the CPU will drop to the lowest P-mark by default and stay put. Why can't I just clock the CPU in BIOS and be done with it? What's even more strange is that while the MSR is running as a Windows service, the CPU goes back to 800 MHz unless I stop and start the service upon login. I set this in task scheduler and it's working automatically but I'm really curious as to why I need to do this as well.

Thanks!

 

[VirtualLarry]

If you're booting a 125W CPU in a 95W-max board, then sure, the mobo / BIOS is going to throttle the CPU, just to keep the board and the VRMs alive.

Or the BIOS simply doesn't properly recognize that later CPU, and needs an update.

 

[DrMrLordX]

Sounds like the board's BIOS does not have correct support for the CPU. Even with a weak VRM, you should be able to undervolt/underclock the CPU and run it as you like.

 

[Ratman6161]

I'm dusting off some truly ancient knowledge here, but it appears as though an AM3 CPU could work on an AM2 board. I say could. according to Wikipedia: "Socket AM3 processors are able to run on Socket AM2 and AM2+ motherboards with appropriate bios updates," See https://en.wikipedia.org/wiki/Socket_AM2

Checking Wikipedia, they say that your CPU was released in August 2009 where as the newest bios for your motherboard is from April 2009 and its listed as a beta bios at that. The newest official bios is from April 2008 and probably doesn't support the Phenom IIsince it pre-dates Phenom II. I would say your only chance would be to try that 2009 beta bios if you have not done so already.

 

[Assoul]

The board reads and shows the CPU's model number just fine, but I think I should go with a lower Phenom that's actually supported, unless there's a way to tweak the BIOS and get it up-to-speed with this model.

The closest supported CPU on this board (and yes, I do have the latest BIOS) would be the Phenom II 925, which I don't think is that far away from the 965 (who will miss a measly 500MHz?). Asus doesn't have the 965 but they do have the 925 listed. I'm debating if I should just go with that one and call it a day. Unless, there's something I'm missing that can get this thing to run correctly.

 

[DrMrLordX]

Either go with the 925 or keep using Phenom MSR Tweaker. I've used msr tweaker software before. It's a bit janky, but it gets the job done.

 

[Assoul]

Replaced it with a Phenom 945 and it works perfectly. Overclocked it from 3.0 to 3.4 GHz and it returns the same performance benchmarks as the 965. It loads a lot faster when loading Windows as well.