The M-II tested by AnandTech had no problems handling FSB speeds up to 100MHz on Super7 motherboards. Unlike older 6x86MX processors which simply wouldn't work at the 100MHz FSB, the M-II 300 didn't seem to have many apparent problems with the setting. Using the FIC VA-503+ Revision 1.1B, which unofficially supports the 112 and 124MHz FSB frequencies, the M-II 300 would consistently crash under Windows 9x and in spite of reliable operation for a limited period of time, the M-II test system would not work reliably enough at those two particular settings to be considered an option.
Even using a higher core voltage setting wouldn't allow the M-II 300 to pass the 233MHz mark reliably. The test system would boot at 250MHz (83 x 3.0) but stability, as mentioned before, wasn't solid enough to be considered a viable overclocking option (Winstone crashed 3 of the 5 times run). The next in the M-II line, the M-II 333, should prove to be much more of an overclocker as it is a 0.25 micron chip which will produce less heat and operate at a lower (2.5v) core voltage setting than current M-II processors. In comparison to the other Socket-7 processors out currently, the M-II is an extremely poor overclocker as the 233MHz part wouldn't even make it past 250MHz. Increasing the core voltage on the M-II didn't help too much to increase stability, the sweet spot for the M-II 300 seemed to be the 3.0v - 3.1v region, 3.2v just caused more problems than it created, and anything above that is simply out of the question for a stable system.
Unlike the AMD K6-2, the M-II from Cyrix doesn't require a special motherboard to get the most performance out of it. The processor will receive a 2 - 5% increase in performance on motherboards that supports its unique form of Linear Burst SRAM addressing. Motherboards based on non-Intel chipsets generally support Linear Burst Mode, such as those based on VIA chipsets, support for this feature isn't required but it is a nice plus for owners of motherboards that support the setting.
Strong business application performance is what makes the M-II the chip it is, and not an odd looking 486. An ever present weakness of Cyrix processors has been their extremely weak FPU performance, meaning 3D gaming performance on an M-II is pretty much unacceptable in comparison to the competition's performance. Because of this poor FPU, the M-II has gained a poor reputation among gamers and it is the main reason that the reputation of Cyrix processors in general has suffered so greatly.
Cyrix vs the Rest
How does the M-II stack up to the competition? Providing business application performance equivalent to a K6 300 or Pentium II 300, Cyrix does offer a lot of bang for the buck. Considering the M-II 300 can be purchased for just under $100, and considering that it offers performance in general business applications (i.e. Microsoft Word, Surfing the Net, etc...) that is competitive with the rest of the competition, the M-II stacks up quite well. In essence, you can consider the Cyrix M-II the opposite of an Intel Celeron in that it has outstanding business performance at the tradeoff of poor 3D gaming performance.
While Cyrix has been boasting that the performance of the M-II is greater than that of the Intel Celeron, you must keep in mind that the Celeron and the M-II are geared towards two completely different markets. There is no way that the M-II can compete with any of the other 6th generation processors on the market in terms of 3D gaming performance, even when armed with a Voodoo2 accelerator, the performance of the M-II 300 under Quake 2 is barely reaching 30 fps. The Celeron has an extremely strong FPU and is therefore much better for gaming, whereas the M-II has a considerably weaker FPU but offers business application performance equivalent to that of a Pentium II.
In comparison to a K6, you may want to go ahead and purchase a K6 over an M-II provided that you have the extra cash to make up for the difference in price. The K6, especially the K6-2, is much more of a well rounded chip when it comes to performance. Although the raw FPU power of both the K6 and K6-2 is considerably slower than that of a Celeron/Pentium II, the FPU of the K6 is still considerably more powerful than that of the Cyrix M-II making it a better option for users with gaming intentions as well as productive ones for their computer.