x2 4200 vs. x2 5200 BE

One of two things likely happening,

1. Being mis-reported from the bios. If you haven't double check what it shows for teh vcore in the bios hardware monitoring section (it should show the vcore in addition to the rest of the voltage readings), and compare to what it shows in CPU-Z.

2. The vcore is set to auto in the bios and is running higher than the rated vcore (happens a lot on Asus motherboards).

If you haven't seen it here are the specs for that CPU,

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For #1 if what it shows in the bios is at or near 1.325-1.375V, then there is nothing to do but remember the difference when checking with monitoring software.

For #1 and #2 if it is showing the same as in CPU-Z, then you need to go into Advanced section of the bios and under "AMD Overclocking Configuration", manually set the vcore to either 1.35 or 1.375V.

I would, then leave it there for a few days and test things out to make sure it is stable there (it should be). Also with that much drop in voltage you should see lower CPU temps; I saw around 5-6°C drop on my last CPU that was over-volted on the auto setting after manually setting it to what it should have been.

As for Q-Fan, unless you can hear the CPU fan over anything else, I would just leave it alone.

The Vcore fluctuation can be from a couple of things, and it's not always BIOS related:

1. The system PSU may not be strong enough. Most PSUs don't put out their advertised Wattage, and if they do, it's usually a maximum that can't be sustained very long. You may be right at the edge of what your PSU can deliver right now. If you go into the BIOS and look at the +12V and 5V rails, and they fluctuate a lot, it's usually a good indication that your PSU isn't up to the job.

2. The sensor chip may not be reading the voltage sensor correctly.

3. You have a possible MOSFET problem. This is potentially serious, or possibly not. In the worst case scenario, the MOSFETs are weakened or failing, and no longer are able to supply a stable voltage to the CPU. Over time, the voltage drift will get larger, or the FETs will fail altogether and either cut off the Vcore, or short out and raise it to 3.3V or higher. In that case, it's bye bye CPU.

4. Your capacitors are beginning to fail.

It's not worth panicking about number 3, because there isn't much you can do about it, other than replace the motherboard. Unless you have access to surface mount soldering tools, and some technical know-how, you can't fix it. A half decent motherboard is relatively inexpensive, so having a tech repair it for you may not be cost effective.

First off, check your power supply in the BIOS, and then with some monitoring software. Speedfan does a nice job of voltages. Keep an eye on the drifting. If it starts to get worse, I would suggest a new board.

The fluctuation could also be caused by Cool and Quiet, which I'm pretty sure is enabled by default on most if not all Asus motherboards. As for it reading higher than the specs for the CPU say, Asus boards are well known for overvolting the CPU when the vcore setting is left on auto.

To give one example of how it overvolts the CPU, I had it happen to me with my current motherboard and a x2 7750 (according to spec is 1.05-1.325V, range to account for CnQ). With the vcore set to auto, both in the bios and any monitoring software it showed as running at around 1.43V or so, a far cry from the 1.325V the spec says. I had to manually set it to get it to run at the proper volts. Once I did that the bios and monitoring software showed the proper values, and an added bonus it dropped something like 7-8°C from the idle and load temps.

The fluctuation is only 16 mV. I think fluctuations by CnQ would be larger. In the area of 100 to 200 mV. If I enable CnQ on my PC, the voltage range is 1.15 to 1.36. A difference of 210 mV. Very different than what the OP is experiencing. Of course, my board isn't an ASUS, so I might be wrong.

Unfortunately AMD doesn't list a range on the 5200 (3 versions),

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like they do for yours (0.875-1.5V ) or my (0.90-1.425V) CPU's.

I wonder if the 5200's CnQ profile is really all that developed? Some of the older AMD chips didn't have it at all, and the 5000 series is fairly old in CPU terms.

I just checked at CPU World, and the 5200 does have CnQ, but the Vcore range is pretty small 1.3 to 1.35 for one of the Brisbane cores, and it's pretty typical of the others. If CnQ is going to work on that one, the variance is only about 50 mV, assuming it doesn't go below the minimum. I would think that on the 5200, it probably only lowers the multiplier. That would be my guess, anyway.

The newer generation stuff, like Athlon II's and Phenom II's, are quite aggressive in power consumption, depending on the motherboard. My Foxconn doesn't really lower the voltage as much as I'd like, and it likes to overvolt, too, but it does do the job.