                  WHAT UPGRADE CHIPS ARE AVAILABLE?
                     Submitted by: Gloria Short



  If the miasma of numbers and letters in the chip names is giving
  you a headache, perhaps a few words of explanation can help clear
  it up.


  Intel Corporation designs the original PC chips, from the first
  8088 processor in the original IBM PC to the latest CPU chip, the
  Pentium (which would have been the 586 had Intel not felt a need
  to abandon its number-naming scheme). After each new generation
  of chips is released, others clone them by creating as compatible
  a chip as they can. AMD--Advanced Micro Devices--has been at it
  the longest, joined in recent years by Cyrix. As we go through
  the mug book of current chips, you'll see both AMD and Cyrix
  chips, along with the Intel chips.

  Starting from the chips you'll be swapping out, here's the lineup
  of today's chip market.

  INTEL 386SX. Available in speeds from 16 MHz to 33 MHz, this
  workhouse chip uses a 32-bit bus internally and a 16-bit bus
  externally while offering full 386 multitasking capabilities. It
  has the equivalent of 275,000 transistors.

  INTEL 386DX. The DX model is the full 386 chip, running at 16 MHz
  to 33 MHz and using a 32-bit bus both internally and externally.
  It also has the equivalent of 275,000 transistors.

  INTEL 386SL. Available in 20 and 25 MHz speeds, the 386SL is
  similar to a 386SX in that it uses a 32-bit internal bus and a
  16-bit external bus. It was designed for use in laptop computers,
  because it has both cache and memory controllers on board and
  uses less power. Created after the 486 chip for this special use,
  it has 855,000 transistors.

  AM386DX. This is the monopoly-busting 386DX chip from AMD,
  running at the speeds of 25, 33, and the unique 40 MHz. It uses a
  32-bit bus both internally and externally and accomplishes this
  with only 161,000 transistors. Its lower price at introduction
  forced Intel to drop its prices.

  AM386SX. AMD's popular 386SX is like the Am386DX except for its
  16-bit external bus. Several power-saving features were built-in,
  so it consumes 35- percent less power than Intel's 386SX.

  INTEL 486SX. Available in 16 to 33 MHz models, this
  900,000-transistor chip is a 486DX with the math coprocessor
  masked off. It uses a 32-bit bus both internally and externally
  and has an 8K internal cache. Its enhanced microcode also
  contributes to its speed.

  INTEL 486DX. Running at 25, 33, and 50 MHz, the 486DX uses
  1,200,000 transistors, a built-in math coprocessor, an 8K cache,
  and enhanced microcode to perform its high-speed magic. It uses a
  32-bit bus internally and externally. (Trivia: The 486DX is 50
  times faster than the 8088 chip in the original IBM PC.)

  INTEL 486DX2 OR OVERDRIVE CHIP. The DX2 doubles the internal
  clock speed of a 25-MHz 486DX to a speedy 50 MHz, or doubles a
  33-MHz 486DX to an even speedier 66 MHz. The speed increase is
  only within the CPU; the external bus runs at the original clock
  speed. When sold to be used in a new computer, it's called a DX2.
  When sold as an upgrade, it's an OverDrive chip.

  CX486SLC. This 20, 25, or 33 MHz chip from Cyrix uses an internal
  32-bit bus and a 16-bit external bus. With only 600,000
  transistors, a 1K cache, and no math coprocessor, it's different
  from an Intel 486SX or DX. Intel argues that it's really more a
  386 than a 486.

  CX486DLC. This one is Cyrix's true 486-compatible chip, with a
  32-bit data path internally and externally, a 1K cache, a
  built-in math coprocessor, and 600,000 transistors.

  CX486DRU.SUP.2. Cyrix's name-convention-busting Cx486DRu.sup.2
  chip is Cyrix's answer to Intel's DX2/OverDrive chip. It's a
  600,000 transistor clock-doubler designed as a replacement unit.
  (DRu stands from Direct Replacement upgrade.) It's available to
  double the speeds of 16, 20, and 25 MHz machines. Its bus, of
  course, is 32-bits internally and externally. It's a little
  taller than an Intel 386DX chip, so it may not fit into computers
  with limited headroom over the chip socket.
