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AMD was kind enough to send us a Phenom 9600 Black Edition processor - the 2.3GHz Phenom with an unlocked multiplier that they are targeting computer enthusiasts with.

As we have already covered the Phenom 9600 in our earlier review and the Phenom 9900 launch articles, we wanted to take the opportunity in this article to explore the overclocking potential of this unlocked processor, and also investigate the performance effects of the fix for the TLB erratum.

Just how far can this overclocking enthusiast chip be pushed, and how much performance will we really lose by enabling the microcode fix?

A quick recap of the Phenom architecture:

• quad core
• integrated DDR2 memory controller
• shared 2MB L3 cache
• individual 512KB L2 caches per core
• 128 bit FPU
• max 8GB/sec Hypertransport bandwidth in AM2 mode
• max 14.4GB/sec Hypertransport bandwidth in AM3 mode (no AM3 motherboards yet)
• max 12.8GB/sec DDR2 memory bandwidth
• dynamic power management

All the currently available Phenom processors are B2 (or possibly even earlier) steppings, and suffer from what is known as the "TLB erratum" - more plainly put, a "bug" or "defect" in the chip, that can at times cause the chip to lock up and crash. AMD has released two different patches that allow working around the problem - one a microcode fix that is loaded into the processors by the BIOS, and another, which is a kernel patch to RedHat Linux.

The Linux patch causes very little performance loss - some say less than one percent - whereas the microcode fix reportedly causes a 10-20% drop in performance across the board. Unfortunately, as Windows is not open source, AMD has not been able to release a kernel patch for XP or Vista to lower the performance hit of the bug; and Microsoft has not seen fit to build such a patch to date either.

We thought we would take this opportinity to examine the impact of the BIOS fix on the benchmarks we normally use to evaluate processors, and as such, we will run our benchmarks with both the patch enabled and with the patch disabled.