Intel originally designated its processors by number rather than by name—Intel 8086, 8088, 80186, 80286, and so on. Intel dropped the “80” prefix early in the life cycle of the 80386, relabeling it as the 386. (Intel never made an “80486” processor despite what some people believe.) By the time Intel shipped its fourth-generation processors, it was tired of other makers using similar names for their compatible processors. Intel believed that these similar names could lead to confusion among customers, and so tried to trademark its X86 naming scheme. When Intel learned that part numbers cannot be trademarked, the company decided to drop the “86” naming scheme and create a made-up word to name its fifth generation processors. Intel came up with Pentium.
Intel has produced the following three major subgenerations of Pentium:
These earliest Pentium CPUs, first shipped in March 1993, fit Socket 4 motherboards, use a 3.1 million transistor core, have 16 KB L1 cache, and use 5.0 volts for both core and I/O components. P54-based systems use a 50, 60, or 66 MHz memory bus and a fixed 1.0 CPU multiplier to yield processor speeds of 50, 60, or 66 MHz.
The so-called Classic Pentium CPUs, first shipped in October 1994, fit Socket 5 and most Socket 7 motherboards, use a 3.3 million transistor core, have 16 KB L1 cache, and generally use 3.3 volts for both core and I/O components. P54C-based systems use a 50, 60, or 66 MHz memory bus and CPU multipliers of 1.5, 2.0, ...