For Immediate Release Contact: Michael Krech, Director 

Serious Undocumented Performance Flaw on all x86 Processors

Surrey, U.K.    - February 11, 1998 -

Intelligent Firmware Ltd, today announced that it discovered a serious undocumented flaw in all x86 processors which significantly reduces their performance.
This performance flaw is an internal imperfection in x86 processorsí bus unit which constantly hampers memory and secondary cache bandwidth with the result of significantly reducing overall system performance.

The company also released information on the workaround to this flaw which completely reverses the performance loss. But due to the hardware nature of this flaw, it can be bypassed only at the programming level; that is by (re)writing a few parts of a program in a different way, the flaw can be neutralized. Intel's recommendation for optimum performance is to access data sequentially (page 43, 3.5.3, Intel Architecture Optimizations Manual) which causes the flaw to happen, while by accessing data in a special non-sequential order bypasses the flaw.

For most people, this performance flaw is more important than all these Pentium bugs that were found in the past 3 years. For instance, the worst bug, the FDIV bug, occurred only on 1 in 9 billion double precision divisions and then only returned a slightly wrong result. Intel correctly stated that this bug affected only a small minority (at most 1-2%) of its customers. But this performance issue affects everybody all the time, because everybody would have a faster processor if the bus unit didn't have this flaw, or if programmers, compiler makers, etc. were aware of that.

All recent x86 processors have the flaw and on all of them the flaw can be bypassed by accessing data in a special non-sequential way, except AMD K6 on which the flaw is permanent (i.e. it occurs on all ways of transferring data).

Much more information, bar charts, a schematic demonstration and in-depth technical analysis can be found at our non-commercial informative web site at <>.

About Intelligent Firmware Ltd
Intelligent Firmware Ltd is a small system software research company located in Surrey, United Kingdom. In the past 11 years it has been researching new ways of computer using, new intelligent languages and innovative system software & hardware, programming only in assembly language.

Intel and Pentium are registered trademarks of Intel corporation. All other trademarks are those of their respective owners.

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