The TLB bug in AMD's Phenom Quad Core processors is fixable ... but at a price. A drop in performance drop is expected.

Introduction

In recent months AMD has had its fair share of problems. Last year since the merger of AMD and ATI, the company has suffered huge losses ... some analysts believe that the merger was the biggest mistake ever made in I.T. history. Intel on the other hand has announced massive profits every quarter. The delay of ATI's next generation GPU towards the end of 2007 hasn't helped either. Their flagship Radeon HD3870 graphics card, which uses their latest RV670 GPU was no match against Nvidia's Geforce 8800GT (G92). And if you think that things could get worse, AMD's announcement of their next generation "Spider" platform received poor publicity due to its lacklustre performance against the Intel Core 2 Quad. Not to mention the recent TLB bug found on their Phenom Quad Core processors.

Although these problems may sound serious, it's not the end of the world ... and there are always fixes. For starters, AMD will be preparing to attack the market more agressively in 2008. Their Tri-Core processors, which will be due out 2nd quarter of this year, is said to be cheaper than Intel's Core 2 Duo. And sure enough, we'll find out whether these Tri-Core CPUs will mean better peformance than the Dual Cores. There's also AMD's flagship high-end processor, the Phenom FX, which have yet to be released. On top of that, AMD have just released their highest performing graphics card in the form of the Radeon HD3870x2. It uses 2 RV670 GPUs on a single PCB, with Crossfire configuration already configured and ready to go. Preliminary tests have shown that the HD3870x2 looks very promising.

Now for the other headache ... the TLB bug. This bug was only recently discovered at the end of 2007, and is predominently found on AMD's Phenom Quad Core processors B2 stepping. I don't want to get too technical, but this erratum (as its known) involves the chip's translation lookaside buffer (TLB) and L3 cache. Although there's no guarrantee that the bug will manifest itself, it could happen during periods of high utilization of all four CPU cores. And this can lead to the data corruption and system hangs. To fix this bug, AMD have outlined a solution which involves a simple BIOS update on your motherboard. But the only thing is ... you get a performance drop when this BIOS-based workaround is enabled. I guess that's the Sacrafice they had to make.

However, there are some good news on the way. AMD will be releasing their B3 steppings in February, which has the TLB bug fixed. This hopefully will give some kind of credibilty to AMD. It will be interesting  to see what performance we'll get with this new B3 stepping. The review sample that AMD sent us, is an engeering sample of their Phenom processor (B2 stepping), which still has the TLB bug. It has a multipiler of x13 and runs at 2.6Ghz. I must remind you that this processor is only compatible with AM2+ motherboards, with a 940-pin socket. Now if you look at the current models of the Phenom, AMD has not released the 9900 yet, which supposed to run at 2.6Ghz. I guess they're going to wait until February before they'll release the 9800 model with the TLB bug fixed ... period.

         

We'll be testing this processor on a MSI K9A2 Platinum motherboard, which uses AMD's latest 790FX chipset. It supports DDR2 ram, 2000Mhz Hyper Transport and has 4 PCIe slots for Crossfire X configuration. To counter the TLB bug, MSI have included a patch in the BIOS which allow users to enable or disable this feature.

We're not expecting the Phenom to outperform the Intel Core 2 Quad processsor. We already know that. However, what we will be investigating, is whether the AMD Phenom can complete all our benchmarks and how the BIOS-based workaround affects the overall performance.

OK, let's take a closer look at the technical specifications of the AMD Phenom processor ...