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Print 64 comment(s) - last by clnee55.. on Dec 24 at 2:33 AM

Much of AMD's bad luck over the last three months revolves around a nasty bug it just can't shake

Erratum, to those in the hardware or software industry, is a nice way of saying "we missed a test case" during development and design. 

Yesterday, The Tech Report confirmed AMD's iteration of Intel's F00F bug.  The bug, which has been documented since at least early November, can cause a deadlock during recursive or nested cache writes. 

How does the TLB erratum occur?  All AMD quad-core processors utilize a shared L3 cache.  In instances where the software uses nested memory pages, this processor will experience a race condition. 

AMD's desktop product marketing manager Michael Saucier describes a race condition as a series of events "where the other guy wins who isn't supposed to win." 

In the software world, a typical memory race condition occurs when the memory arbiter is instructed to overwrite an older block of memory, but write the old block of memory to somewhere else in cache.  In the instance where two arbiters follow this same rule set, its easy to see how a race condition can occur: both arbiters attempt to overwrite the same blocks of information, resulting in a deadlock.

From what AMD engineers would tell DailyTech, this example is very similar to what occurs with nested memory pages in virtualized machines on these K10 processors. 

AMD has since released a new BIOS patch for all K10 motherboards, including the often cited but rarely seen MSI K9A2 Platinum.  This patch, confirmed by DailyTech, will result in at least a 10% reduction in general computing speed. 

AMD partners tell DailyTech that all bulk Barcelona shipments have been halted pending application screening based on the customer.  Cray, for example, was allowed its latest allocation for machines that will not use these nested virtualization techniques.  Other AMD corporate customers were told to use Revision F3 (K8) processors in the meantime. 

The TLB erratum will be fixed in the B3 stepping of all AMD quad-core processors, including Phenom and Barcelona.  However, AMD considers the B3 stepping a "March" item on its 2008 roadmap.  Processors shipped between then and now will still carry the TLB bug, though with the BIOS workaround these machines will not experience a lockup. 

The delayed Phenom 9700 is affected by the TLB bug, though AMD insiders tell DailyTech the upcoming 2.6 GHz Phenom 9900 is not affected.  This indicates Phenom 9900 will carry the B3-stepping designation.

AMD's latest roadmap hints that its tri-core processors are merely quad-core processors with one core disabled. The company also indicated that it will introduce some of these tri-core processors with the L3 cache disabled.  Removing the shared-L3 cache from the chip design eliminates the TLB bug.

In a likely-related event, AMD's newest corporate roadmap scheduled three Phenom processors for the first half of 2008; one of which is the Phenom 9700.  The company will launch eleven new 65nm K8 processors in the same time period.


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RE: Not good
By qwertyz on 12/5/2007 2:08:58 PM , Rating: -1
AMD should cease to develop any more CPUs since they are unable to create BUG free products.
AMD should go bankrupt instead of delivering bogus CPUs


RE: Not good
By Oregonian2 on 12/5/2007 2:18:27 PM , Rating: 2
ROTFL


RE: Not good
By Oregonian2 on 12/5/2007 3:10:38 PM , Rating: 3
Somebody appears to not have liked my laughing at the obvious tongue-in-cheek joke that someone posted (*ALL* processors ever produced in the history of semiconductors have had bugs in every version produced -- even the comparatively trivial 8080/Z80 processors had bugs in nice eratta sheets (I design embedded processor systems and have since the 8008 processor (as the HW circuit designer))).


RE: Not good
By Myrandex on 12/5/2007 2:41:37 PM , Rating: 2
[sarcasm] Hell Yeah! Especially since no other CPU manufacturer ever has bugs in their designs! Also Software should be held to these standards, so no more Software can be sold again since none is bug free! [/sarcasm]


RE: Not good
By Clauzii on 12/5/2007 5:46:42 PM , Rating: 2
Talking about flicking the big red switch :o


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