It is likely Cyrix could have continued to successfully sell processors based on Socket 3, but canned the 5x86 so that it would not compete with its then new 6x86 offerings.
The official Cyrix 5x86 website boasted about several features of the chip that were disabled by default in the final versions.
While it was possible to enable the extra features using a special software utility, it usually resulted in an unstable system, especially on earlier steppings of the chip when running 32-bit code.
The 133 MHz version is very rare, however, and producers of upgrade kits were given preferential access to it, notably Gainbery.
IBM's 5x86C was considered to be more conservatively rated than the Cyrix branded parts, and operated at a lower voltage (3.3V).
A few examples of 120 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.