Also see the Pentium MMX and the Pentium 3.
The Pentium is a widely-used personal computer microprocessor from the Intel Corporation. First offered in 1993, the Pentium quickly replaced Intel's 486 microprocessor as the microchip-of-choice in manufacturing a personal computer. The original Pentium model includes two processors on one chip that contains 3.1 million transistors.
The Pentium Pro, released in 1995, was designed for PC servers and workstation that needed to serve multiple users or needed the speed required for graphics-intensive applications. In addition to the microprocessor, the Pentium Pro includes another microchip containing cache memory that, being closer to the processor than the computer's main memory (RAM), speeds up computer operation. The Pentium Pro contains 5.5 million transistors.
The Pentium II is a Pentium Pro with Intel's MMX technology included. It comes in microprocessor clock speeds of 233 MHz (millions of cycles per second), 266 MHz, and 300 MHz. It's suitable for applications that include motion video and 3-D images. Among the Pentium II's features are a 512 KB (kilobyte) level-two (L1 and L2) memory cache and a 32 KB L1 and L2 cache, twice that of the Pentium Pro processor. The L2 cache can include error correcting code (ECC).
The latest Pentium II's are Celeron, a low-end Pentium without the L2 cache, and Xeon, a high-end Pentium that replaces the Pentium Pro for enterprise server and workstation computers.