Editing Cyrix 6x86 (section)

==Performance==
Similarly to [[Advanced Micro Devices|AMD]] with their [[AMD K5|K5]] and early [[AMD K6|K6]] processors, Cyrix used a [[PR rating]] (Performance Rating) to relate their performance to the Intel [[P5 (microarchitecture)|P5]] [[Pentium (brand)|Pentium]] (pre-[[P55C (microprocessor)|P55C]]), as the 6x86's higher per-clock performance relative to a P5 Pentium could be quantified against a higher-clocked Pentium part. For example, a 133&nbsp;MHz 6x86 will match or outperform a P5 Pentium at 166&nbsp;MHz, and as a result Cyrix could market the 133&nbsp;MHz chip as being a P5 Pentium 166's equal. However, the PR rating was not an entirely truthful representation of the 6x86's performance.<ref>{{Cite news |last=Phillips |first=Jon |date=July 2000 |title=The Pre-Fab Debate Continues |volume=5 |pages=16 |work=[[Maximum PC]] |publisher=[[Future US, Inc.]] |issue=7 |url=https://books.google.com/books?id=5QEAAAAAMBAJ&dq=cyrix+PR+rating&pg=PA16 |access-date=5 April 2022 |issn=1522-4279}}</ref>

While the 6x86's integer performance was significantly higher than P5 Pentium's, its floating point performance was more mediocre—between 2 and 4 times the performance of the 486 FPU per clock cycle (depending on the operation and precision). The [[Floating point unit|FPU]] in the 6x86 was largely the same circuitry that was developed for Cyrix's earlier high performance [[8087]]/[[80287]]/[[80387]]-compatible coprocessors, which was very fast for its time—the Cyrix FPU was much faster than the 80387, and even the 80486 FPU. However, it was still considerably slower than the new and completely redesigned P5 Pentium and [[P6 (microarchitecture)|P6]] [[Pentium Pro]]-[[Pentium III]] FPUs. One of the main features of the P5/P6 FPUs is that they supported interleaving of FPU and integer instructions in their design, which Cyrix chips did not integrate. This caused very poor performance with Cyrix CPUs on games and software that took advantage of this.<ref>{{Cite web |last=Mury |first=John |title=CPU Considerations; Cyrix |url=https://www.oocities.org/timessquare/fortress/6191/cpu.html |access-date=7 April 2022 |website=NiNe's Rendition Quake Workshop}}</ref><ref>{{Cite web |last=Hsieh |first=Paul |date=7 September 1999 |title=6th Generation CPU Comparisons; The Cyrix 6x86MX |url=http://www.azillionmonkeys.com/qed/cpuwar.html |access-date=7 April 2022}}</ref>

Therefore, despite being very fast clock by clock, the 6x86 and MII were forced to compete at the low-end of the market as AMD K6 and Intel [[P6 (microarchitecture)|P6]] [[Pentium II]] were always ahead on clock speed. The 6x86's and MII's old generation "486 class" floating point unit combined with an integer section that was at best on-par with the newer P6 and K6 chips meant that Cyrix could no longer compete in performance.