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Pentium MMX

This Article was last modified in October, 1998.

The Pentium Processor With MMX

The Intel Pentium Processor with MMX Technology

The Pentium MMX processor offers some significant improvements over the original Pentium processor, in particular, its' ability to handle multimedia applications much more efficiently. It is currently available in clock speeds of 166, 200, and 233 mhz, for desktop systems, as well as 133, 150,166, and now 200, 233, and the new 266 MHz for mobile systems.

Improvements over Pentium Classic

The Pentium MMX technology boasts three primary architectural design enhancements over the original Pentium classic:

New Instructions
Intel engineers have added 57 new instructions specifically designed to manipulate and process video, audio and graphical data more efficiently. These instructions are oriented to the highly parallel, repetitive sequences often found in multimedia operations.

For all of you that really want to know more, here's a link to the specifics of the new MMX Instructions.

Today's multimedia and communication applications often use repetitive loops that, while occupying 10 percent or less of the overall application code, can account for up to 90 percent of the execution time. A process called Single Instruction Multiple Data (SIMD) enables one instruction to perform the same function on multiple pieces of data. It allows the chip to reduce compute-intensive loops common with video, audio, graphics and animation. Also, the MMX instruction set has the ability to pair up two MMX instructions in one cycle, therefore 2 SIMD instructions can be processed with 16 byte data in one clock cycle.

More Cache
Intel has doubled on-chip cache size to 32K (16KB data, and 16KB instruction cache) on the Intel Pentium processor with MMX technology. Now, more instructions and data can be stored on the chip, reducing the number of times the processor has to access slower, off-chip memory areas for information. Also, the data cache is now 4 way set associative, whereas in the Pentium classic it is only 2 way set associative.

Improvements Based on other CPU's
The Pentium MMX has improved by taking some of the stronger components of other CPU's. The Pentium MMX now includes a branch prediction unit, which was taken from Intel's own Pentium Pro, and also has an implementation of a Return Stack, as known from the IBM/Cyrix 6x86's.

Other Improvements
The Pentium MMX also now has double the write buffers of a Pentium classic, 4 instead of 2. Its' U and V Pipelines have also been increased by one step. And the Parallel Processing Ability of the two pipelines has been improved.

New Voltages
The Pentium MMX requires split voltages, whereas the Pentium classic, used a single voltage setting. The Pentium MMX requires at least 2.8V for the CPU core, and 3.3V for the CPU I/O interface. So even though the Pentium MMX is supposed to be Socket 7 compatible, you may need to purchase a new motherboard that supports split voltages if you wish to use a Pentium MMX CPU.

CPU-Central Scoring

Overclockability 90%
3D Performance 85%
Overall Performance 80%
Upgradability 85%
Compatibility 99%
Price 60%

Overclockability: Again (as in the classic Pentium), due to Intel's high quality standards (which result in their high prices), the overclockability of their CPU's is very high. However, some of these CPUs have their higher multipliers locked internally, and increasing the bus speed is the only way to overclock them.

3D Performance: As in the Pentium classic, the FP unit in this chip performs very well, and therefore leads to excellent 3D performance. Also, the MMX instructions in this chip help it perform better in many 3D games and applications.

Overall Performance: The Pentium MMX performs greatly in multimedia games and applications, and even better in those designed specifically for the Pentium MMX. In normal applications, due to the slight improvements in the chip over the Pentium classic, such as the doubling of the cache, the Pentium MMX still performs quite better than the classic Pentium.

Upgradability: Since these chips use split voltages, the motherboards that they are used with should be compatible for many of the future Socket 7 chips to come, and the current ones such as the K6, and the 6x86MX, as well as all Pentium OverDrive CPU's.

Compatibility: Since Intel's CPU's are the standard, most games and applications are specifically tuned for them, and therefore virtually and PC program will work on this chip. Also, the new batch of software that uses MMX instructions should definitely work on these chips.

Price: Intel continues to drop the prices of their MMX processors in order to keep up with the competition. However, the price of these CPUs are still quite high compared to their competitors, such as the K6 and 6x86MX, which perform almost the same, or better, than the Pentium MMX.


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