AMD Phenom TLB Patch Benchmarked and Explained

Benchmarking The BIOS Workaround

The Test System

Phenom Test Platform
Component	Brand/Model	Live Pricing
Processor	AMD Phenom 9900	Click Here
Motherboard	MSI K9A2 Platinum w/Bios 121	Click Here
Memory	OCZ PC3-12800 FlexXLC 4GB	Click Here
Video Card	XFX GeForce 8800 GTX	Click Here
Hard Drive	Western Digital SATA Raptor 150GB	Click Here
Cooling	Corsair Nautilus 500	Click Here
Power Supply	Corsair HX620W	Click Here
Monitor	Soyo 24″ Widescreen LCD	Click Here
Operating System	Windows Vista Ultimate 32-bit	Click Here

The test system was running Windows Vista Ultimate 32-bit with all available Microsoft updates including the hotfixes required for enthusiast video cards to run correctly. NVIDIA Forceware 169.25 drivers were used on the XFX GeForce 8800 GTX graphics card. The MSI K9A2 motherboard was tested using four 1GB memory modules at 4-4-4-12 2T timings with 2.1V.

Benchmark Results

Using the PCMark Vantage test suite the difference between having the TLB patch workaround enabled and disabled was night and day. The system didn’t feel any slower on the test bench, but the results showed differently. The performance difference ranged from 2% to 11.7% depending on the testing. It’s obvious that the TLB workaround impacts performance.

Yesterday we showed how Sandra XII wasn’t properly optimized for Phenom processors on the memory bandwidth test, so we are using Sandra XII SP1 now. Without the TLB patch the Phenom 9900 (2.6GHz) processor was able to break 10,300 MB/Sec, which is impressive. With the patch enabled performance dropped 6.55% and the memory bandwidth was down to 9600 MB/Sec.

Final Thoughts:

AMD dropped the ball when it comes to how they informed failed to tell the community anything about the erratum other than a fix was coming out. The fix created a significant performance hit, which was bound to look bad for them. Sure it can be disabled in OverDrive, NOW. When the BIOS patches started to be sent out to the media the TLB patch couldn’t be disabled in the BIOS and AMD didn’t tell us a way to disable it was coming out in overdrive. AMD OverDrive versions 2.0.12 and newer have the ability to disable the patch, but it’s hidden in the utility.

By using the ‘turbo’ button one can disable the TLB BIOS patch when using the yellow or red ‘turbo’ settings. By pressing the turbo button the ring around the button will change color as seen in the picture above. We asked AMD what the different settings on the turbo button do and we were informed the following.

• Green = safe
• Yellow = faster
• Red = fastest

It doesn’t adjust any clock speeds.

We asked AMD if they could go into more details on what exactly these settings are doing, but it has been days and they have not commented. To be honest we have asked more than one person in AMD what these settings do and either they don’t know or don’t reply. The one thing we know it does is disable the TLB patch for erratum 298, which is a good thing for those that want a performance boost. Personally, I think it should be either an option that can be either enabled or disabled and one that is clearly marked. In the mean time I’m going to try and figure out what the turbo settings are really doing. If you own a Phenom processor and update your BIOS to one that has the performance fix be sure to get the latest version of OverDrive to disable the TLB workaround. We have yet to see it on any of our systems and unless you are running VMware it’s likely you won’t run into it either.

Down the road when a new stepping of the Phenom processor comes out this will all be a thing of the past. AMD says a fix is in place and the new revision of silicon will not have a performance hit. Good news can be found if you just look deep enough!

Legit Bottom Line: AMD fails to communicate a performance crushing erratum to the media. They then provide motherboard companies a BIOS fix with, but there is no way to disable the BIOS workaround. AMD then releases new OverDrive versions that can disable it with a mystery ‘turbo’ button.