Turning Zosma Into Thuban
Preliminary information on Zosma is still scarce, and since we didn’t get this processor from AMD, pricing data isn’t available. What we do know is that the Phenom II X4 960T runs at a stock 3 GHz clock rate and supports Turbo CORE technology. It also sports a 95W TDP, down from the 125W of AMD’s Phenom II X6 1090T flagship (naturally, that changes when you start turning on cores, overclocking, and upping voltages).
Now, you might have thought that core unlocking as a feature was dead, since AMD pulled ACC out of its SB850 southbridge. And for a while there, it was looking like the most visible motherboard vendors wouldn’t pursue core unlocking in the 8-series chipsets. Asus was the first to break rank, though, and others have since followed suit, enabling unlocking via a number of mechanisms.
On ASRock’s 890FX Deluxe3, you can either turn on core overclocking through a BIOS switch called ASRock UCC or by simply hitting the ‘x’ key during POST (subsequently pressing ‘d’ during POST turns off UCC). Naturally, our Phenom II X4 960T was chosen for its ability to unlock reliably. Temper your enthusiasm, though. Our sources at ASRock tell us that, out of 16 samples the company has tested, six are able to unlock to six cores. That's a 37% chance in a fairly small sample size.
Four cores, 3.9 GHz Six cores, 3.6 GHz
Do Unlocked Cores Hurt Overclocking?
If we assume that at least a percentage of locked cores are marginal compared to the four cores AMD leaves enabled, then turning those two disabled cores on risks system stability, increases power consumption, and very likely hurts your chances to hit as aggressive of an overclock.
We tested this out a bit using our Phenom II X4 960T sample and found that hitting 3.9 GHz was not a problem for this 3 GHz chip using a 1.425V BIOS setting. Turning on the two locked cores forced us down to 3.6 GHz to avoid crashing as Windows loaded up, and the extra heat forced a voltage reduction to 1.4V.
The moral of the story is (and this should be no surprise) turning on disabled cores will likely cap your maximum overclock on conventional air cooling, even if those cores are determined to be “good.” Weighing the pluses and minuses of pursuing parallelism or frequency will likely be a matter of evaluating the software you’re running. An extra 900 MHz from a 3 GHz quad-core chip on air is impressive. Those are the numbers we’d expect from an Intel Core i5 or i7 CPU, so it’s good to see AMD’s improved 45 nm process yielding additional scalability.