The Jargon File (version 4.4.7, 29 Dec 2003):
The name given to Intel's P5 chip, the successor to the 80486. The name was
chosen because of difficulties Intel had in trademarking a number. It
suggests the number five (implying 586) while (according to Intel)
conveying a meaning of strength ?like titanium?. Among hackers, the plural
is frequently ?pentia?. See also Pentagram Pro.
Intel did not stick to this convention when naming its P6 processor the
Pentium Pro; many believe this is due to difficulties in selling a chip
with ?hex? or ?sex? in its name. Successor chips have been called Pentium
II, Pentium III, and Pentium IV.
The Free On-line Dictionary of Computing (18 March 2015):
Intel's superscalar successor to the 486.
It has two 32-bit 486-type integer pipelines with dependency
checking. It can execute a maximum of two instructions per
cycle. It does pipelined floating-point and performs
branch prediction. It has 16 kilobytes of on-chip
cache, a 64-bit memory interface, 8 32-bit general-purpose
registers and 8 80-bit floating-point registers. It is
built from 3.1 million transistors on a 262.4 mm^2 die with
~2.3 million transistors in the core logic. Its clock rate
is 66MHz, heat dissipation is 16W, integer performance is 64.5
SPECint92, floating-point performance 56.9 SPECfp92.
It is called "Pentium" because it is the fifth in the 80x86
line. It would have been called the 80586 had a US court not
ruled that you can't trademark a number.
The successors are the Pentium Pro and Pentium II.
The following Pentium variants all belong to "x86 Family 6",
as reported by "Microsoft Windows" when identifying the CPU:
1 Pentium Pro
3 Pentium II
5, 6 Celeron or Pentium II
7 Pentium III
8 Celeron uPGA2 or Mobile Pentium III
A floating-point division bug
(ftp://ftp.isi.edu/pub/carlton/pentium/FAQ) was discovered in
[Internal implementation, "Microprocessor Report" newsletter,
1993-03-29, volume 7, number 4].
[Pentium based computers, PC Magazine, 1994-01-25].