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AMD Phenom 9850 Black Edition
by Marc Prieur
Published on April 9, 2008



At the launch of the Phenom last November, we unfortunately noted that its performances were not too competitive with those of the Q6600 (the equivalent of 86% the latter). However, shortly thereafter, another more serious problem appeared: the TLB bug.

This erratum that was discovered in early December affects the B2 revision of Phenom and Opteron processors and causes the machine to crash when there is strong use of the TLB (Translation Look-aside Buffer, a part of the CPU which accelerates the translation of virtual memory addresses into physical addresses). Amongst those applications that can put strain on the TLB, AMD mentioned virtualization.

In practice, it’s possible to go around this bug by deactivating the problematic part of the processor on the bios level on the motherboard or with a program (AMD Overdrive) but this also strongly reduces cache efficiency. The solution wasn’t too viable in the long term and notably impacted performances so it was necessary that AMD correct the bug. This is now a thing of the past with this new revision of the Phenom.
Impact of the TLB bug:
Before moving on, let’s come back to the impact on performances of the TLB bug when we use the work-around proposed by AMD :


As you can see, performances are noticeably reduced. With WinRAR compression and the TLB fix we are only at 58% of the CPU’s performances!
The Phenom B3
The launch of this new revision wasn’t done discreetly as new model numbers were attributed. Thus, the Phenom 9500 and 9600, set at 2.2 and 2.3 GHz become the Phenom 9550 and 9650 in their B3 revision. AMD also took advantage of the occasion to raise the frequency of the Phenom 9750 and 9850 with the help of the new stepping.


For this test, AMD sent us a Phenom 9850. Set at 2.5 GHz, this processor is part of its Black Edition series and its multiplier coefficient can therefore be set higher or lower. By default, it is powered by 1.3V versus 1.25 for a Phenom 9600.
Performances
Here are the performances obtained with a Phenom 9650 and Phenom 9850 compared to the Phenom 9600 « B2 » :


At equivalent frequencies, B3 stepping shows slightly higher scores than its predecessor. It’s nothing exceptional but a 1.8% gain in Crysis or WinRAR is always appreciable, all the more so that this time there is no TLB bug.

The increase in frequency of course has a positive impact on performances and scaling in CineBench is almost perfect (8.4% better for an 8.7% higher frequency).


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