Cyrix 5x86

Released in August 1995, four months before the more famous Cyrix 6x86, the Cyrix Cx5x86 was the fastest CPU ever produced for Socket 3 computer systems. With better performance in most applications than an Intel Pentium processor at 75 mhz, the Cyrix Cx5x86 filled a gap by providing a medium-performance processor option for ageing 486 Socket 3 motherboards (which are incapable of handling Intel's Pentium CPUs, apart from the Pentium Overdrive).

The processor was based on a scaled-down version of the "M1" core used in the Cyrix 6x86. It had the 32-bit memory bus of an ordinary 486 processor, but internally had much more in common with fifth-generation processors such as the 6x86, the K5, and the Intel Pentium.

The similarly-named IBM 5x86 was a licenced rebranding of the Cyrix design (IBM physically produced Cyrix's CPUs for them), marketed seperately but identical for practical purposes, apart from the availability of a 75mhz edition which Cyrix did not bring to market, and slight differences in voltage requirements. The Cyrix/IBM 5x86, however, should not be confused with the similarly-named AMD Am5x86 which was essentially a fast 486 (not an all-new design like the Cyrix part) but which had broadly similar performance, used the same Socket 3, and was introduced at the end of the same year.

Specifications:

iDX4WB pinout, 168 pins
Socket 3
2.0 millions transistors on 0.65 micron process
144mm² die
3.45 volt electricity usage
16kilobyte unified level-one cache

100mhz capable edition for 33mhz (33x3) and 50mhz (50x2) front side bus
120/133mhz capable edition for 40mhz (40x3) and 33mhz (33x4) front side bus. The 133 MHz version is very rare, however.

External Links:

Comparitive performance benchmarks
Cyrix 5x86
Cyrix 5x86 Processor Brief
Entry in 486 processors chart