The 6×86, released in 1995, was Cyrix’s sixth generation processor, also nicknamed the M1. This chip was reasonably fast for the time and was a smart way to get decent speed without the hefty price tag. It was, though, an entry-level processor.

Cyrix, by this time, was a major player in the alternative processor market. They had been around since 1992, with their release of the 486SLC. By 1995, they had their own 5×86 processor and it was considered the only real competition to the AMD counterpart. 6×86 was designed to go head to head with Intel’s Pentium processor. Dubbed “M1″, the chip contained two super-pipelined integer units, an on-die FPU, and 16 KB of write-back cache. It used many of the same techniques internally as the Intel and AMD chips to increase performance. Like AMD beginning with their K5 (see below), Cyrix used the P-rating system. It came in PR-120, 133, 150, 166 and 200 versions. Each rating had a “+” after it, indicating that it performed better than the corresponding Pentium. But, did it?

Cyrix had had a reputation for lagging in the area of performance, and the M1 was not an exception. The chip used a weaker FPU than both AMD and Intel, meaning it could not keep up with the competition in areas such as 3D gaming or other math-intensive software. On top of that, the chip had a reputation for running hot. Users had to get CPU fans that could keep these hot processors cool enough to run stably. Cyrix tried to combat this issue with the 6×86L processor. This “low power” processor made use of a split voltage (3.3 volts for I/O and 2.8 volts internally).

Below are the specs on the chip, provided by Cyrix.

6×86MX

Of course, with the craze for MMX processors, Cyrix just had to make one. The 6×86MX was their answer. Formally the M2, it was an enhanced version of the 6×86 with support for the MMX instruction set. It also boasted 64 KB of cache and some enhancements to the FPU. Cyrix almost completely shifted its attention to this new chip. They abandoned the original 6×86, but they still spent money on the MediaGX. The first M2’s were 150 MHz chips, or a P-rating of PR166 (Yes, M2’s also used the P-rating system). The fastest ones operated at 333 MHz, or PR-466.

M2 was the last processor released by Cyrix as a stand-alone company. In 1999, Via Technologies acquired the Cyrix line from it’s parent company, National Semiconductor. At the same time, Via also acquired the Centaur processor division from IDT.

Benchmarks indicated that it outperformed the Pentium MMX/233 and the Pentium Pro/200. The chip actually ran at 187 MHz, so Cyrix continued the PR-Rating system, calling it a PR-233. Like the K6, it fell slightly short in its MMX capability and FPU. For 3D performance, the 6×86MX was the worst of the top chips. Even with a high-end graphics card (for the time), it fell way behind the Pentium MMX/233. Although on business applications, it compared favorably with the Pentium II, it didn’t even compare when it came to 3D software, such as AutoCAD.

The Cyrix attained its speed even though it actually ran at a slower clock speed. This is because Cyrix actually designed the chip to operate at a 75MHz bus speed, while both Intel and AMD had designed their chips for the 66MHz bus. Below is a table of the bus speeds used for the various 6×86MX chips.