Editing Cyrix 5x86 (section)

==Controversies and anomalies==
{{original research|date=February 2017}}
The official Cyrix 5x86 website boasted about several features of the chip that were disabled by default in the final versions. The most controversial of these features was the [[branch prediction]] feature, which was enabled in the benchmarks results on the company website when comparing the chip to Intel's Pentium processor. While it was possible to enable the extra features using a special software utility, it usually resulted in an unstable system, especially on earlier [[stepping level|steppings]] of the chip when running 32-bit code.

There are also many rumours surrounding a 133&nbsp;MHz, clock-quadrupled version of the Cyrix 5x86. The 133&nbsp;MHz version is very rare, however, and producers of upgrade kits were given preferential access to it, notably Gainbery. Some of the 100 and 120&nbsp;MHz parts also contain support for the 4X multiplier setting, and some of these chips may also work at 133&nbsp;MHz. However, the 5x86 is not known to overclock well; 120&nbsp;MHz is generally considered to be pushing the limitations of the process on which it was fabricated. An 80&nbsp;MHz (2×40&nbsp;MHz) 5x86 also exists, but is unclear as to whether or not it was ever officially released.

IBM's 5x86C was considered to be more conservatively rated than the Cyrix branded parts, and operated at a lower voltage (3.3V). For example: what Cyrix would rate as a 100&nbsp;MHz part, IBM would mark as 75&nbsp;MHz. IBM 5x86C was available as 75&nbsp;MHz and 100&nbsp;MHz parts. A few examples of 120&nbsp;MHz parts also exist, but they have early production dates indicating that they may have been produced prior to IBM's decision to scale back clock speeds. 5x86C also had a much longer production run than the Cyrix branded parts. IBM continued to produce 5x86C at least until late 1998 ([[Quad Flat Package|QFP]] only), whereas Cyrix's own part was discontinued in 1996. Parts which implement the 4X multiplier or Stepping 1 Rev 3 cores are not known to exist.