Pentium II

The Pentium II is an x86 architecture microprocessor by Intel, introduced on May 7, 1997. It was based on a modifed version of the P6 core first used for the Pentium Pro, but with improved 16 bit performance and the addition of the MMX instructions which had already been introduced on the Pentium MMX.

The original Klamath Pentium IIs ran at 233 and 266 MHz and produced (for that time) an incredible amount of heat. This was because of the 0.35 µm fabrication process. They also worked with a 66 MHz front side bus, which was a speed that was inadequate for the CPU's design to show its full potential. A 300 MHz version was released later in 1997.

The Deschutes core Pentium IIs which debuted at 333 MHz in January 1998 were produced on a more suitable 0.25 µm fabrication process, meaning they ran significantly cooler. Support for 100 MHz front side bus speeds heralded decent performance improvements. During 1998, Pentium IIs running at 350, 400, and 450 MHz were also released. Pentium II-based systems also oversaw the introduction of the new generation RAM-standard, SDRAM (which replaced EDO RAM), and the AGP graphics bus.

Unlike previous Intel processors such as the Pentium and Pentium Pro, the Pentium II was packaged in a slot-based form-factor rather than a socket one. This larger package was a compromise allowing Intel to separate the secondary cache from the processor while still keeping it on a closely coupled bus. This separate cache was slower (running at half the processor speed) than that in the Pentium Pro, but solved the Pentium Pro's low yields allowing Intel to introduce the Pentium II at a mainstream price level.

A low-end version of the Pentium II - essentially a Pentium II with less (or sans) level 2 cache - was marketed under the name "Celeron". The Pentium II Xeon was a high-end version intended for use on servers.

By early 1999, the Pentium III superceded the Pentium II.