Cyrix 6x86

6x86/MII
A Cyrix 6x86-P166 processor
General information
Launched
  • 6x86 - Oct 1995
  • 6x86L - Jan 1997
  • 6x86MX - Jun 1997
  • MII - May 1998
Discontinued
  • 6x86 - Jun 1999
  • 6x86L - Jun 1999
  • 6x86MX - May 1998
  • MII - Early 2000s
Marketed by
Common manufacturers
Performance
Max. CPU clock rate80 MHz to 333 MHz
FSB speeds40 MHz to 100 MHz
Cache
L1 cache
  • 16 KB (6x86/L)
  • 64 KB (6x86MX / MII)
Architecture and classification
ApplicationDesktop
Microarchitecture6x86
Instruction setx86-16, IA-32
Physical specifications
Transistors
  • 4.3M 500 nm
Cores
  • 1
Sockets
Products, models, variants
Core names
  • M1
  • M1L (Low voltage)
  • M1R (3M to 5M)
  • MII (MMX)
Variant
  • 6x86, 6x86L, 6x86MX
History
PredecessorCyrix 5x86
SuccessorCyrix III

The Cyrix 6x86 is a line of sixth-generation, 32-bit x86 microprocessors designed and released by Cyrix in 1995. Cyrix, being a fabless company, had the chips manufactured by IBM and SGS-Thomson. The 6x86 was made as a direct competitor to Intel's Pentium microprocessor line, and was pin compatible.

During the 6x86's development, the majority of applications (office software as well as games) performed almost entirely integer operations. The designers foresaw that future applications would most likely maintain this instruction focus. So, to optimize the chip's performance for what they believed to be the most likely application of the CPU, the integer execution resources received most of the transistor budget.

This would later prove to be a strategic mistake, as the popularity of the P5 Pentium caused many software developers to hand-optimize code in assembly language, to take advantage of the P5 Pentium's tightly pipelined and lower latency FPU. For example, the highly anticipated first-person shooter Quake used highly optimized assembly code designed almost entirely around the P5 Pentium's FPU. As a result, the P5 Pentium significantly outperformed other CPUs in the game.

After Cyrix was bought by National Semiconductor then later VIA, the 6x86 continued to be produced up until the early 2000s.