Theo Valich from The Inq claims the reason why AMD only has 2.2GHz and 2.3GHz Phenom processors is because the chips have an error in the Transition Lookaside Buffer (TLB). The 2.2GHz and 2.3GHz parts have the problem too but it seems that the chip only starts malfunctioning at clockspeeds of 2.4GHz or above:
We asked AMD to provide us with official statement on this huge problem, and we got a reply back from the firm:
"The Translation Lookaside Buffer (TLB) errata is an L3 protocol issue causing a system hang when running certain client workload applications independent of platform. AMD is immediately introducing an updated BIOS which will correct the TLB errata".
This problem was found during speed-binning the B2 revision processors, and this was the cause for the Phenom FX 3.0 GHz delay. It turns out that some CPUs running at 2.4 GHz or above in some benchmarking combinations, while all four cores are running at 100% load, can cause a system freeze.
A B3 revision of the Phenom processor should fix the problem:
AMD already issued a fix to all of its motherboard/system partners, so if you already own a 790FX motherboard or plan to buy a Phenom system, make sure to update the BIOS. 9500 (2.2 GHz) and 9600 (2.3 GHz) parts are unaffected by the errata. Some 9500/9600 parts may even be overclocked to 2.6, 2.8, 2.9, 3.0 GHz and they will have no problems whatsoever, while some will have this error. In any case, you should update the BIOS of your shiny new Phenom system is clocked higher than 2.4 GHz.
According to sources close to the company, 2.4, 2.6, 2.8, 3.0 and faster parts will appear on the market when the B3 revision comes to life. B3 revision is key CPU stepping for AMD's future, since it is considered a speed-bin of B1 and B2. With this errata fixed, Phenoms will have no problems competing against Intel in clock-per-clock action, but it will bring serious disappointment to AMD fanboys and market itself. They are probably blubbing already.