AMD Phenom 9850 Black Edition

AMD Phenom 9850 Black Edition - BeHardware
>> Processors

Written by Marc Prieur

Published on March 31, 2008

URL: http://www.behardware.com/art/lire/713/

Page 1

Introduction, TLB, Performances

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).

Page 2

Consump., Overclocking, Conclusion
Power consumption
We measure power consumption of the processor’s power supply stage with the help of an ammetric clip on the ATX12V connection line which it uses exclusively. This allows us to better isolate CPU power use instead of obtaining overall consumption. The only thing we should keep in mind is that the CPU power supply stage has an efficiency of between 80 and 90%.

Compared to our Phenom 9600 Black Edition, the Phenom 9850 Black Edition posts high power consumption whether in stand-by, semi-load or in full load.
Overclocking
While our first Phenom 9600 which was used in our test in November attained 2.65 GHz at 1.3V, the Phenom 9600 « Black Edition » we received this time didn’t want to go above 2.5 GHz, a quite disappointing result.

On the other hand, the Phenom 9850’s scores are more encouraging because starting at 2.5 GHz we were able to attain 2.8 GHz while maintaining the initial 1.3V. Unfortunately, when increasing voltage, we couldn’t get a stable 2.9 GHz ; however, 2.8 GHz with 4 sessions of Prime95 didn’t pose any problems with this CPU.

Of course, knowing that this CPU comes from AMD and that we were only able to get our hands on the one model, we really couldn’t draw any solid conclusions. However, knowing that AMD took advantage of the B3 stepping to add 200 MHz on commercial versions, it only seems logical that the B3s will go further in frequency.
Conclusion
Contrary to the Phenom B2, the B3 is actually a potential alternative to Intel’s solutions. Of course, a Phenom 9850 is not on the exact same overall level as the Q6600 but it should come very close (roughly 95%) for an equivalent price.

Despite these improvements, we have two criticisms. On the one hand, the frequencies of these Phenoms are is still relatively low in the broad context of things. This deprives AMD of a true high end CPU and doesn’t help it to rival in terms of overclocking. The second criticism is the noticeable increase in power consumption which should at least be resolved by the transition to 45nm ; however, unfortunately this isn’t planned until the last quarter of the year.

In the meantime, Intel should widen its gap even more because its long awaited 45 nm quad core is starting to appear. For this reason, we can no longer compare the Phenom 9850 with the Q6600 but rather to the Q9300. It’s a duel we will come back to in the near future; however, it should largely be in the favor of Intel’s processor. With the Phenom B3, AMD does better but probably not enough.