Cranking up the clocks
Once I was done futzing around with BIOSes and workaround stuff, I pretty quickly headed... well, right back to the BIOS for an overclocking attempt. I started out thinking I'd want to overclock the Black Edition primarily using OverDrive, since the utility has an auto-tuning feature that's supposed to help seek out your CPU's limits. However, after a number of system locks without making any real progress, I decided it was time to go old-school once more. I also decided to switch over to the Asus M3A32-MVP Deluxe motherboard for my overclocking attempts because its BIOS offered some options I wanted.
In this context, the OverDrive utility still proved quite useful thanks to its nifty built-in performance test that stress tests all four Phenom cores at once.
I've long used Prime95 for this task, because I like how it throws an error when it gets a wrong result, even if the error isn't enough to cause a system crash. However, firing up four instances of Prime95 is a bit of a chore, and OverDrive makes it easy. You can even specify how long you want the stability test to run, which is nice. During the iterative steps of an overclocking attempt, just surviving a few minutes is good enough to confirm whether a particular setting is stable enough to justify moving on.
I started out using nothing more than a stock AMD cooler for the Black Edition. My first attempt was at 2.5GHz, or 200MHz above the 9600's stock speed, with a stock 1.25V. The system would POST and boot into Windows at those settings, but quickly crashed. Bumping the chip up to 1.275V was all I needed to get the Phenom to pass a three-minute session in the OverDrive stability test, though.
So, I figured, it was time to move on to 2.6GHz. This is, after all, not unfamiliar territory. We have a Phenom engineering sample that will run fine all day at 2.6GHz. Surely this one would do the same.
The system would POST at 2.6GHz but hang before booting Windows. I tried upping the voltage to 1.3V and 1.325V, to no avail. At this point, frustrated, I began to doubt the ability of the stock cooler to do the job I was asking of it. Fortunately, I had the means to remove all doubt at my disposal, and so I did, by installing this:
That's a Cooler Master Hyper 212, a cooler roughly the size of a human head.
Ok, maybe a smaller human's head, not quite the equal of the jumbo-sized noggin on a hardware reviewer. But you get the picture.
I started with that cooler at 1.325V and still, the system hung shortly after POST at 2.6GHz. I tried raising the voltage as high as 1.3625V, but nothing changed. I even tried backing down to 1.3V and 1.2875V, hoping the additional cooling might work there, but no. This particular chip seems to have a pretty hard limit at 2.6GHz, unfortunately. I'm probably a wuss for not taking the chip to 1.4V and beyond, but I've found that increasing voltage usually only helps improve stability incrementally; this thing wasn't even making it through the initial stages of the boot process.
I decided to call it good at 2.5GHz, and I took my official screenshot at that speed as incontrovertible proof of the clock frequency I'd achieved.
I wasn't done there, though. As you may know from this page of our Phenom review, among other sources, the Phenom architecture's memory access latency and overall performance is affected quite a bit by the speed of the chip's L3 cache. That cache runs at the speed of the chip's north bridge, not the CPU core clock, so there's some real performance potential hiding in the Phenom's north bridge clock. With just a little coaxing, I was able to get our Black Edition north bridge stable at 2.2GHz, or 400MHz above stock.
In order to demonstrate the impact of core and north bridge overclocking, I ran a couple of sets of quick benchmarks on the Black Edition: one with just the cores overclocked to 2.5GHz and another with the north bridge at 2.2GHz, as well.
So there you have it. At 2.5GHz with a 2.2GHz north bridge, the Phenom 9600 Black Edition is definitely more potent than at stock speeds, but the differences aren't massive. Still, overclocking with an unlocked multiplier is dead easy, and when you're finished, all of the system's HyperTransport, PCI, and other clocks are still running at their stock, stable speeds.
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