Overclocking the AMD Phenom II X4 965

So I no longer need the Phenom II rig, and I am about to start selling the parts off. I decided to do something I haven’t done a whole lot in the past: overclocking.

So I knew from previous reviews from a good while ago that the Phenom II range wasn’t that great for overclocking – you were lucky to hit 4GHz in a lot of cases. You needed a pretty decent board and a lot of voltage to hit those clocks. But I decided it was time to try it out, since I had only ever been as far as 3.7GHz in the past.

The system I used had an ASRock M3A790GXH/128M. This was a well featured board that suited my needs well – 140W TDP CPU support, 4 RAM slots, plenty of storage options (even had floppy!), plenty of PCI-E slots (I ran 3850’s in CrossFire back in the day).

The CPU I used was the original 965: the 140W monster C2 variant. The later C3 stepping reduced the overall TDP to 125W, which would have helped my cooling (I used a CoolerMaster Hyper 212 Plus).


So I prepared a xubuntu install to use for benchmarking and stress testing, and I used Phoronix Test Suite to run the benchmarks.

I was able to get to 3.8GHz quite easily, with 1.475V with the RAM running at 1600MHz. Here are the c-ray scores below:


STOCK results refer to complete BIOS default settings (CPU 3.4GHz, RAM 1333MHz). Here we can see that an overclock of 400 MHz yielded an increase of 11% in C-Ray times (C-Ray is used to benchmark ray-tracing operations, and is very taxing on a system). Running the RAM at 1600MHz didn’t affect the results of this test very much, but there is a slight difference. I ran some memory benchmarks:


Running from stock speeds to 1600MHz resulted in quite a big jump in memory bandwidth (CPU frequency didn’t seem to affect the results very much here). This was the first platform AMD did with DDR3, and their memory controllers were not that great at first. Now on my FX-6300 rig, I can hit 10.2GB/s in this benchmark at DDR3-1333. I will be upgrading to 1866 soon though.

The other benchmark I tried was FFMpeg, since I wanted some real-world results:


Interesting! FFmpeg seems to like memory bandwidth quite a lot. CPU speed has a slight impact here – the times get slightly better going from 3.6 to 3.8.

Unfortunately, 3.8GHz was the highest I was able to get. I tried for 3.9, but even at 1.55V the system would crash at the C-Ray benchmark. I tried lowering the RAM back to 1333 and even 1066 to see if that helped, but it didn’t. I decided not to go above 1.55V since I wanted to be able to sell the parts off and not blow them up, and I was already hitting 60-65 degrees at those voltages (the “safe temperature” for this CPU is 62 degrees C (according to¬†CPU-World), and the heatsink was getting very warm. I used another fan to cool off the VRM on the motherboard, since it was probably putting out over 200W into the CPU.

So I wasn’t able to go above 3.8 GHz unfortunately. I thought about this, and came up with a few reasons:

  • My motherboard hasn’t got a strong enough VRM (or other motherboard related stufff)
  • I was unlucky in the “silicon lottery”
  • My chip is 6 years old, and has possibly degraded over time (maybe also the motherboard)
  • My PSU only had a 4-pin CPU connector (yeah I know), so that probably didn’t help
  • I’m not brave enough to go over 1.55V

I’ll try to sell the parts, but if I am unsuccessful, I might be posting back with more overclocking endeavours (there might be flames), so be sure to follow my blog if you would like to see that.

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