Getting Down to BusinessFor this little quick and nasty overclocking article I am using both the new Black Edition Phenom 9600 as well as the unreleased Phenom 9900 engineering sample. The motherboard is the Asus M3A32-Deluxe which is based on the AMD 790FX chipset with the 0603 BIOS. Here is the full list of components:
- Phenom 9600 and 9900
- Asus M3A32-Deluxe
- Corsair DDR-2 1066 @ 5:5:5:15 timings
- XFX 8800 GTX XXX Edition
- Seagate 7200.10 320 GB Hard Drive
- Lite-On DVD-R/RW
- Thermaltake Pure Power 600 Watt Power Supply
- Windows Vista 64 Ultimate
- AMD OverDrive 2.0.13 beta
The Grim Reality
If a user is expecting to get to 3 GHz with their Phenom easily, then they will be sorely disappointed. At this time I only had the use of the very good, but very stock cooler that AMD provided with this setup. Higher end coolers and water cooling equipment will produce better results than what I can show here, but even then getting to the higher speeds will be challenging.
I was only able to achieve a stable overclock to 2.8 GHz with the provided tools. With more aggressive cooling as well as pushing the voltage up higher than I was comfortable with, then 2.9 GHz and 3.0 GHz would be possible. Note that with the current BIOS and AMD OverDrive, there is no way to adjust the northbridge portion’s multiplier. During all of this testing the NB ran at 2.0 GHz. So let’s see how this processor scales with raising the clockspeed. At 2.8 GHz with 1.4v the chip quickly went above 60C with the cooling fan going as fast as it could.
Performance actually scales pretty nicely with the clock speed increases, but we have to wonder how much better it would have been if the NB portion was able to be clocked higher than 2 GHz. If I was willing to do a bit of hex editing on the motherboard BIOS, then I would have the ability to increase that multiplier. However, myself and the vast majority of users are not exactly comfortable messing around with the BIOS at such a low level and potentially bricking their motherboard.
We see a lot of strange results here. We get some increases in main memory bandwidth, but they are really variable. Only when looking at the cache performance do we see increases due to the L2 caches being clocked higher.
The Phenom 9600 runs at a core 2.3 GHz with the NB running at 1.8 GHz. As such we should expect scaling to be a little bit poorer, and overall memory performance down from the 9900. When I clocked this part to 2.5 GHz with 1.35v it also quickly exceeded 60C with the fan going full speed on the heatsink.
2.6 GHz was unattainable with the current equipment I have. If I had been willing to push voltage higher, it would likely have hit 2.6, but cooling becomes a big factor here. I was not fond of the idea of pushing the core above 70C, so I stopped at 2.5 GHz. I would guess with water cooling or peltier cooling that 2.7 would have been achievable, but 2.8 GHz is far from a guarantee.
I was curious as well to see how performance scaled with the NB running at a lower speed than in the 9900 sample.
We see something quite interesting here. If we scale these results for the 9600 to 2.6 GHz, it ends up being slower than the Phenom 9900 at a stock 2.6 GHz. For example the ALU performance of the 9600 @ 2.6 would be around 35,000 while the 9900 gets around 35,500 MIPS. This is not a huge difference, but we do see the effects of running the NB portion at a lower speed. In memory and cache performance, the difference is far larger.
The memory bandwidth for the Phenom 9600 is cut down by about 800 MB/sec from the 9900. The extra 200 MHz the NB on the 9900 has over the 9600 does have a fair sized effect on memory performance. Cache performance… not so much. It scales about how it should. Then again, all the L2 caches are run at full core speed.