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The IBM/Cyrix 6x86 Processor
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The IBM 6x86 is in fact an IBM manufactured and labelled Cyrix 6x86. Cyrix entered the fifth generation processor market with the 6x86 processor, formerly projected as the M1. As a successful and cheaper (often less than half the cost) alternative to the Intel Pentium, it is pin- and voltage-compatible with it. Cyrix gave it the 6x86 name in reference to some of its more advanced features, which it calls "sixth generation". In reality, the processor is comparable in power and architecture to the fifth-generation Pentium.
The 6x86 is not a Pentium clone. Clones are exact or near-exact copies, usually being reversed engineered or based on licensed code. The 6x86 is based on an original Cyrix design. It incorporates several advanced architectural features that allow it to outperform a Pentium of equal clock speed. For this reason Cyrix helped invent the "P-Rating" system. This was an advantage to help people make a valid comparism but also caused some confusion when setting the appropriate clock speed on the motherboard.
The Cyrix 6x86 range has the most powerful processor core of any x86 processor of its generation. Unfortunately, like the AMD K5, it also has a very slow floating point math capability and so was a very poor games and 3D performer.
The processor is designed for Socket 7 and is available in several clock speeds, some of them rather unusual. The 6x86 PR200 (150 Mhz) processor introduced non-standard bus speeds up to 75 MHz - many motherboards and PCI cards did not support this speeds: Since the PCI bus runs at half of the mainboard bus speed, you are increasing the PCI bus to 37.5 MHz with a bus speed of 75 MHz. Several PCI cards, especially some graphics cards, did not run correctly with this overclocked bus.
References:
Cyrix 6x86 Processor Brief
Cyrix 6x86 Processor FAQ
Cyrix Press Releases |
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| The earlier versions of the 6x86 had problems with heat and power consumption. Responding to customer complaints, Cyrix came out with a lower powered version called the 6x86L. This processor reduces power consumption by 25% or more compared to the original 6x86. It uses a smaller, 0.35 micron circuit size and split voltage much like the Pentium MMX (3.3V external, 2.8V internal). |
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The IBM/Cyrix 6x86MX Processor
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The IBM 6x86MX is in fact an IBM manufactured and labelled Cyrix 6x86MX.
The successor to the 6x86 and 6x86L is the 6x86MX (M2), intended to compete with AMD's K6 and Intel's Pentium MMX. The 6x86MX is an evolutionary step from the 6x86 and is very similar to it in internal function.
The 6x86MX supports the MMX extension and also features several other improvements over the original 6x86 chip. The internal cache was increased from 16 to 64 KB, a 256 byte additional pre-cache was added to help improve efficiency in how the regular level 1 cache is operated, the Branch Prediction was improved and the internals of the chip have been optimized for 32-bit operation.
References:
Cyrix 6x86 Processor FAQ
Cyrix Press Releases
Cyrix 6x86MX Press Tour |
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This is a very early version without the 6x86 logo and P-Rating.