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Intel Pentium MMX


Intel Pentium MMX: Image courtesy of Intel Corporation

January 1997 saw the first major processor release from Intel since the Pentium Pro in 1995. The processor in question was the Intel Pentium MMX (or P55C to the technicaly minded). This was heralded by a loud advertising campaign which introduced us to the now imfamous dancing "Bunny People™". The Pentium MMX was also significant in that it marked the introduction of a new set of instructions in the guise of "MMX". With the world worked up into MMX frenzy, what exactly did this new chip offer?

The Pentium MMX in profile

The Pentium MMX was marketed as being an almost revolutionary new processor by its makers Intel. The Pentium MMx was in fact an enhancement of the original Intel Pentium processor, but with a significant number of enhancements.

The Pentium MMX was the last iteration of Intel's fifth generation processor architechture. The hugely sucessful Pentium had brought features such as superscalar architechture and a highly advanced floating point unit to the "x86" world. The Pentium MMX was pin compatible with the Socket 7 architechture and offered existing users a clear upgrade path. The only problem though was that the Pentium MMX had a significant difference over the original Pentium. This was that it was designed to run with split voltages unlike the Pentium. Let us explain what this means:

The original Pentium runs with a core voltage of 3.5v and an I/O voltage of 3.5v. The problem with this was that higher clock speeds this was beginning to cause heat output problems as was demonstrated with the Cyrix 6x86+ processor. A solution to this had to be found and the answer was to lower the chip's voltage. The end result was the Pentium MMX running with a core voltage of 2.8v and an I/O voltage of 3.3v, thus the split voltage requirement was needed.

The problem with split voltages is that a great deal of older Socket 7 motherboards cannot handle this requirement and so precluded any upgrade. Only boards manufactured after late 1996 can really handle this requirement.

The Intel Pentium MMX uses a bus speed of 66 MHz and comes in speeds of 166, 200 & 233 MHz. This chip was manufactured using the 0.35 micron manufacturing process. Intel also produced this chip in a mobile version which is manufactured using the 0.25 micron manufacturing process and is available in speeds of 166, 200, 233, 266 & 300 MHz.

The other main feature the Pentium MMX brought was the inclusion of 52 new MMX instructions. These instructions were designed to enhance multi-media applications, enhancing graphics and sound functions. MMX (rumoured to stand for Multi-Media eXtensions, although this was denied by Intel) was the first instruction level enhancement made to "x86" architechture since the 386.

To find out how the Pentium MMX fares today, read on...


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