The Intel Pentium

Dan Knight - September 2001

Intel chose the Pentium name for the next generation CPU, avoiding the expected 586 designation. The Pentium originally shipped at 60 and 66 MHz. It had 3.1 million transistors using 0.8 micron technology. Like the 486, it supported 4 GB of RAM and 64 TB (terabytes) of virtual memory.

The Pentium is a superscalar design, which means it can process multiple instructions at the same time - something we take for granted today. It also had twice the cache space of the 486: an 8 KB instruction cache and an 8 KB data cache.

Just as the 486 was significantly more efficient than the 386 at the same clock speed, the Pentium offered a performance advantage over the 486. Part of this came from the wider 64-bit data bus.

Byte magazine (May 1993) noted that the Pentium had a MIPS (million instructions per second) rating of 112 at 60 MHz or 1.85 MIPS/MHz. This compares very favorably (about 2-1/3x time higher!) with the 0.8 MIPS/MHz rating of the earlier 486DX, although we must keep in mind that MIPS is not an accurate pedictor of real world CPU performance.

In running real world comparisons of the 60 MHz Pentium vs. a 66 MHz 486, the Pentium scored up to twice the performance of the older CPU as reported by the same issue of Byte.

Another way to improve Pentium performance was to use software compilers optimized for the Pentium, a strategy even more important to Intel's new Itanium processsor. According to Byte magazine, Pentium-optimized code was up to 30% faster on a Pentium system and also 5-10% faster on existing 386 and 486 hardware.

Further Reading

• Great Microprocessors of the Past and Present, Intel 8086: IBM's Choice, John Bayko

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