Unfortunately for AMD, one of the most publicized features of the new Barcelona chips is the TLB bug, which in a very few cases can cause a system lockup.  Even a small chance of failure like this makes the Barcelona a far less attractive choice to use in any critical system, and as these chips are aimed at the server market, that becomes a very big deal.  AMD has issued a patch, but the patch comes at a price; we have heard it possibly costs up to 14% of total performance.  A different fix is available for Linux users from x86-64.org, which keeps the TLB alive and uses software emulation to wash those dirty bits.  The Tech Report wanted to see exactly what effect the patch had on a Windows install, and you can see for yourself that disabling the TLB really does hurt performance.

“This week’s developments have included the revelation that this bug affects all “Barcelona” quad-core Opterons, leading to a “stop ship” order on quad-core Opterons to most customers. The erratum also affects all speed grades of Phenom processors, which are still shipping to PC makers and resellers. AMD admitted the presence of the erratum prior to the Phenom’s public introduction, but the firm’s initial statements gave many the impression that the erratum affected only the 2.4GHz version of the Phenom, which it had decided to delay. In truth, all current Phenom variants have the bug, and systems with those processors will have to be patched and suffer the accompanying performance penalty.”

Here are some more Processor articles from around the web:


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