Duane's Homepage : Cyrix 6x86 Series

A Guide To Cyrix/IBM Processors
6x86 / 6x86L / 6x86MX / M-II

General overview The performance of a Cyrix processor doesn't rely on clock speed alone. Cyrix processors tend to have a more efficient architectural design. This explains why the clockspeed (MHz) here does not reflect the actual performance as compared to the other processors. Cyrix uses a performance rating (P-Rating) to categorize their processors. The P-Rating (e.g. PR2/333) gives you the performance class of a Cyrix processor as compared to a Pentium processor.

The Cyrix/IBM 6x86 processor Initially designed to compete with the Intel Pentium Pro, and hence named the 6x86, this CISC processor ended up going head to head against the Pentium instead. Fantasic integer performance allows this chip to outperform the Intel Pentium at lower clock speeds. This chip however has a poor floating point performance (FPU). It runs at 3.3V and fits in a Pentium class (socket 7) motherboard. This processor has only 2x and 3x clock multipliers.

The Cyrix 6x86L processor The 6x86L is a low power version of the original 6x86. Similar in voltage requirements to the Pentium MMX (P55C), this processor has a plane voltage (VCore) of 2.8V. Addressing the heat problems of the 6x86, it runs very cool but still has a poor floating point performance (FPU). This processor fits in a Pentium class (socket 7 motherboard) and is built by a 0.35 micron die process.

**Cyrix/IBM/ST 6x86 Bus Speeds and Multipliers**
CPU	Clock Speed/MHz	Bus Speed/MHz	Clock Multiplier
6x86 PR120+	100	50	x2
6x86 PR133+	110	55	x2
6x86 PR150+	120	60	x2
6x86 PR166+	133	66	x2

The Cyrix 6x86 Processor

6x86 Processor


The Cyrix 6x86MX processor The 6x86MX is an MMX enchanced processor. This chip has 64KB of internal level 1 cache and runs at a plane voltage of 2.8V (VCore). Like the original 6x86, it has an excellent integer performance that outperforms all other 6th Generation processors (including the Pentium 2) when compared at the same clock speed. However, like its predecessor, it also has a poor 32bit and floating point performance (FPU). The processor fits in a Pentium class (socket 7) motherboard and runs on a totally CISC system. The similarity to the 6x86 does not end here, and it thus also uses a PR rating system (albeit a more complicated one called the PR2). Based on this system, the PR2/166 is equivalent to a Pentium 166 MMX. PR2/200 is equivalent to a Pentium 200 MMX, and PR2/233 is the equivalent of a Pentium II running at 233MHz. Cyrix/IBM/ST 6x86MX Bus Speeds And Multipliers

Microprocessor	Clock / Bus	Core Voltage / I/O Voltage

IBM 6x86MX PR166	2.0 / 66 MHz	2.9V / 3.3V
IBM 6x86MX PR200	2.5 / 66 MHz	2.9V / 3.3V
IBM 6x86MX PR233	3.0 / 66 MHz	2.9V / 3.3V
IBM 6x86MX PR233	2.5 / 75 MHz	2.9V / 3.3V
IBM 6x86MX PR266	2.5 / 83 MHz	2.9V / 3.3V
IBM 6x86MX PR300	3.0 / 75 MHz	2.9V / 3.3V
IBM 6x86MX PR300	3.5 / 66 MHz	2.9V / 3.3V
IBM 6x86MX PR333	3.5 / 75 MHz	2.9V / 3.3V
IBM 6x86MX PR333	3.0 / 83 MHz	2.9V / 3.3V

The Cyrix/IBM 6x86MX Processor

6x86MX Processor

Cyrix 6x86MX Processor Competitive Comparison

Processor Features	Cyrix 6x86MX	Pentium® II	Cyrix 6x86	Pentium® w/ MMX^(TM) (P55C)
MMX Enhanced	Yes	Yes	No	Yes
Superscalar	Yes	Yes	Yes	Yes
Superpipelined	Yes	Yes	Yes	No
Register Renaming	Yes	Yes	Yes	No
Data Dependancy Removal	Yes	Yes	Yes	No
Multi-branch prediction	Yes	Yes	Yes	No
Speculative Execution	Yes	Yes	Yes	No
Out-Of-Order Completion	Yes	Yes	Yes	No
80bit Floating Point Unit	Yes	Yes	Yes	Yes
Primary Cache	64Kb	32Kb	16Kb	32Kb
Processor Socket	Socket 7	Slot 1	Socket 7	Socket 7

Continuing the tradition set by the 6x86 processor, the 6x86MX has the best price-performance ratio of the 6th generation processors. Its excellent integer performance and price makes it the most suitable for office environments where word processing, surfing of the internet, spreadsheets and accounting is the main use of the computer. Click Here for the IBM 6x86MX and 6x86 Parts Number History

The Cyrix M-II processor In an attempt to distance themselves from Intel's cheap cacheless offering, the Celeron, Cyrix gave the designation "M-II" to all 6x86Mx processors with a power rating of 300MHz and above. The marketing strategy was meant to highlight that fact that the 6x86Mx series is a competitor of Intel's more powerful Pentium 2 range (note the similarity in the numeral "2"). IBM however, did not follow the lead set by Cyrix and kept to the name 6x86Mx.

The Cyrix Cayenne processor Running on a 100MHz front side bus, this is an M2-series processor that incorporates a AMD's 3D Technology instruction set. The processor also sports a redesigned floating point unit that has double the floating point performance of the conventional 6x86Mx. Clock speeds in the range of 300-400MHz are expected.

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Last modified on July 31, 1998