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Module 3c3. The 5th generations CPUs - continued

  • The P55C - MMX
  • IDT WinChip
  • Voltages - dual voltage
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  • Pentium MMX (P55C)

    The P55C Pentiums were introduced January 8, 1997. MMX is a new set of instructions (57 new integer instructions, four new data types, and eight 64 bit registers), which expand the capabilities of the CPU. It is an addition to the original Pentium set of instructions.

    The MMX instructions were designed for multimedia programs. The programmers can utilize these instructions in their programs. These allow the Pentium to provide improved program execution.

    Both Cyrix and AMD use MMX in their 6th generation CPUs (K6 and M2). Programs, which are written with MMX instructions, can still be run on, for example, a Pentium without MMX. However, execution is slower with the traditional instructions.


    More L1 cache and higher clock frequency

    Compared to the Pentium Classic, the Pentium MMX were further improved with 32 KB L1 cache (the old one had 16 KB). There were also other improvements in the CPU. These improvements together meant 10-20% better performance at similar clock speeds. The clock frequency of the new processors were 166, 200 and 233 MHz.

    Dual voltage

    The P55C required a new motherboard. Not because of MMX - that is pure software, but because of changes in the power supply. The P55C operated with dual voltage technology. To reduce heat generation, this chip requires two different voltages: 2.8 Volt to the nucleus and 3.3 Volt to the I/O section. The old motherboards for the P54Cs have only one voltage to the CPU. Thus, the new CPU requires a new motherboard.


    For use in laptops Intel has a special power-saving version of the Pentium MMX. The so-called Tillamook processor is manufactured using 0.25 micron technology, and you find it in 266 and 300 MHz versions.

    IDT Winchip

    IDT was another smaller company to produce low-priced Pentium MMX-like CPUs. Their first WinChip C6 was introduced in May 1997. The company wanted to deliver 200 MHz Pentium MMXs for $50.

    About the IDT WinChip C6 CPU

  • 5.4 million transistor
  • 0.35 micron, 4-layer metal CMOS technology
  • Socket 7 compatible
  • 200 MHz

    About the WinChip 2 3D, released May 19, 1998

  • Socket 7 processors running at 266 MHz and 300 MHz
  • 0.25-micron process technology
  • 2.5-volt IBM Blue Logic technology
  • 6 million transistors
  • Die size only 88mm2 making it the smallest x86 processor in the world
  • Superscalar MMX and 3DNow!
  • Fully pipelined floating point unit
  • 100 MHz bus support IDT expected to continue the development of their WinChips. They wanted to double up the L1 cache for better performance and to introduce a superpipeline technology, which also will speed up the whole thing.

    We never saw many IDT chips in my country.

    In 1999 the company was taken over by VIA who integrates the IDT technology in their Cyrix processor line.

    Voltages - dual voltage

    One of the most important CPU technologies is the continually thinner wires inside the chip. With thinner wires, the CPU can operate at lower voltage. That results in a smaller CPU generating less heat and with the ability to operate at higher speeds. A step in this development is the design of dual voltage chips:

  • The interface to the I/O bus, which always requires 3.3 volt.

  • In internal CPU parts, it is advantageous to reduce the voltage as much as possible. This can be done because of the extremely thin wires in the CPU. The Socket 7 motherboards have a two part voltage regulator to match the needs of the CPU. Here are some selected CPUs and their voltage requirements:

    CPU Internal voltage I/O voltage
    Pentium MMX 2.8 Volt 3.3 Volt
    AMD K6 2.8/2.9 Volt 3.3 Volt
    Cyrix 6X86MX 2.8 Volt 3.3 Volt
    Pentium II "Klamath"
    2.8 Volt
    3.3 Volt
    AMD K6-2
    2.2 Volt
    3.3 Volt
    Pentium II and III
    2.0 Volt
    3.3 Volt
    Pentium III "CuMine"
    1.6 Volt
    3.3 Volt

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    Learn more

    Or continue with the 6th generation CPUs. Click for Module 3e.

    Read module 5a about expansion cards, where we evaluate the I/O buses from the port side.

    Read module 5b about AGP and module 5c about Firewire.

    Read module 7a about monitors, and 7b on graphics card.

    Read module 7c about sound cards, and 7d on digital sound and music.

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