Cyrix's new 6x86MX PR266 CPU is one of the latest and fastest of the 6x86MX group of processors, and produces the kind of price/performance numbers that make it one of the best CPUs available on the market today.

Once again, Cyrix has pushed forth the bus speed barrier with it's 6x86MX PR266. The PR266 runs at an 83MHz bus speed (the first CPU to "officially" support the 83MHz bus speed), with a 2.5x multiplier, for a total of 208MHz. However, don't let that number fool you; the 6x86MX PR266 will easily outperform the Pentium II 266MHz in normal business applications, and will even outperform the Pentium II 300MHz in certain areas as well.

Architecturally speaking, the 6x86MX PR266 contains basically the same parts as it's predecessors, and is still based on the older and "fatter" .35 micron manufacturing process.

And like it's predecessors, the 6x86MX PR266 is still plagued by a weak FPU unit, and does not come anywhere near the Pentium II's performance in terms of 3D games and applications. Even the older Pentium MMX will outperform the PR266 in the gaming area.

Unlike the previous 6x86MX units, the 6x86MX PR266 runs at a core voltage of 2.7V, which helps it run quite a bit cooler. Unfortunately, some motherboards may not support this odd voltage setting. I have managed run it at 2.8V for quite a while, and have had no problems. In fact, it still runs quite cool (42 degrees celcius with the computer's case off).

The 6x86MX PR266 was previously available only to OEM's, and system manufacturers. Cyrix had refrained from introducing the PR266 individual tray units, due to the fact that there were not a wide selection of qualified motherboards that supported the 83MHz bus speed reliably. Recently, Cyrix has announced that it has decided to skip the PR266 chip, and instead produce a PR300 processor because of better-than-expected manufacturing yields. All of this means that the PR266 will be extremely hard to come by for the end user.

The 6x86MX PR266 is easily overclocked to 75x3=225, without increasing the voltage, or losing any stability. However, anything past that is pretty flaky, even with my huge GlobalWin 25602-16 cooling unit. It'll get into Windows at 249MHz (83x3), or even 262.5MHz (75x3.5), however, you will most likely experience frequent crashes and instability at these speeds; increasing the voltage does not help.

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