Chapter 3: Microprocessors^61
Cyrix 5x86
The Cyrix 5x86, also known as the M1SE, was intended to compete with the Intel 486 with
which it was socket compatible. Like the AMD 5x86, the Cyrix processor was able to
compete with early Pentium processors.The Pentium
Although it was known in its early development as the 80586, by 1992, Intel had discov-
ered that model numbers could not be copyrighted. So, instead of the number, they
used a trademark name, Pentium, for their next processor. This new processor, shown
in Figure 3-13, included many new features, including separate 8-bit caches for data
and instructions and a very fast FPU. The Pentium kept the 32-bit address bus of the 486
but added a 64-bit data bus. It also includedsuperscalararchitecture, which is a processor
technology that allows more than one instruction to be executed in a single clock cycle. The
clock speeds of the Pentium processor ranged from 60MHz to 200MHz.MMX Technology
The next version of the Pentium processor was the Pentium MMX, which had clock
speeds from 166MHz to 233MHz. This version of the Pentium processor added MMX
(Multimedia Extensions) technology to the Pentium along with some improved internal
clock speeds. MMX technology is a set of instructions that uses matrix math (another
meaning for MMX) to support graphic compression and decompression algorithms
(such as JPEG, GIF, and MPEG) and 3D graphic renderings. MMX allows the FPU to act
on several pieces of data simultaneously through a process called SIMD (single instruction
multiple data).Cyrix 6x86 Processors
Cyrix, which is now VIA Cyrix, produced a family of Pentium clone processors that were
designated as the 6x86-P series. The “P” value in the model name was a performance
rating indicator. The 6x86-P200 indicated that the Cyrix processor with that model
number had the performance equivalent of a Pentium 200MHz processor. Cyrix pro-
duced models ranging from its 6x86-P120 to the 6x86-P200. The 6x86-P series had over-
heating problems as well as some incompatibility issues, which prompted Cyrix to
produce a low-power, low-temperature version, the 6x86L.Other Pentium Clones
Two other manufacturers produced processors to compete with the Pentium. The AMD
K5 processor, with versions of 75MHz to 166MHz, unfortunately suffered from its own
complexity, which affected its processing speeds. The Integrated Device Technology