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                               CYRIX 386 to 486
                             UPGRADE MICROPROCESSOR
                               Information Sheet

        Product Description

The Cyrix 386 to 486 Upgrade Microprocessor is the only single
chip microprocessor upgrade designed for 386DX-16, 20 or 25 MHz
computers. It is based on Cyrix 486 technology and features clock doubling,
a 1K on chip cache, Cyrix cache coherency technology (patent pending),
fast I/O and a clock skewing correction circuit. The result of these features
are the benefits of compatibility, data integrity and high performance.

       Key Features and Benefits

     Single Chip Design
  Direct microprocessor upgrade. High quality, dependability and no
  space problems.

     Supports 486 Instruction Set
  Runs all of today's and tomorrow's 386 and 486 software.

     Clock Doubling
  Enhanced performance with the Upgrade Microprocessor running at
  twice the computer's bus clock speed.

On Chip 1K Cache with Cache Coherency Support (patent pending)
  High performance with data integrity

      Fast I/O
  High performance from improved input/output operations of data
  between the microprocessor and the computer's bus.

     Clock Skewing Correction Circuit
  Ensures compatibility with systems whose internal clock may be
  variable.

     Supports DOS, Windows and OS/2 Operating Systems
  Universal Software Compatibility.

    Easy installation
  No additional system modifications.

     III) Implementation of Key Features

        1) Single Chip Design - The Upgrade Microprocessor comes in a
single chip form factor the same size as the 386DX microprocessor. This
single chip design ensures long term reliability and eliminates any
physical space problems found with board style upgrades.

        2) Supports 486 Instruction Set - Based on Cyrix's Cx486 design,
the Upgrade Microprocessor will support all 386 and 486 software applica-
tions available today. This also ensures compatibility for all future
software designed under 386 and 486 industry standards.

        3) Clock Doubling - Clock doubling greatly enhances performance
of all applications, particularly those applications that are processor
intensive. The Upgrade Microprocessor will run at a speed twice that of
the 386DX microprocessor. For example, if the 386DX microprocessor being
upgraded runs at 20MHz, the Upgrade Microprocessor will run at twice the
speed, or 40MHz. Since the system's clock is not adjusted or changed, no
additional FCC approval is required for the Upgrade Microprocessor.

        4) On Chip 1K Cache - Significant performance gains are achieved
withthe Upgrade Microprocessor's on chip cache. This cache is a memory
areawithin the Upgrade Microprocessor that holds data ready to be used by
the processor. Since this data is in the processor, it can be accessed more
quickly than retrieving from the system's memory. This feature is not found
in 386DX microprocessors.

        5) Cache Coherency - Data integrity is assured with Cyrix's cache
coherency technology (patent pending). Since 386 systems are not designed
to support an on chip cache, this technology ensures data integrity between
the internal cache and external memory.

        6) Fast I/O - This is an enhanced feature Cyrix has incorporated into
the Upgrade Microprocessor which is not found in other 386 and 486 micro-
processors. This feature allows the processor to continue processing during
input/output functions to other components of the computer like printer ports, d
isk drives and graphic boards. Fast I/O
will significantly improve video and disk performance where many I/O func-
tions take place.

        7) Clock Skewing Correction - This feature ensures compatibility
where other upgrade products do not. Since tolerances vary with many 386
computer system clocks, Cyrix has implemented in the Upgrade Microprocessor
this mechanism allowing it to adjust to system clock variances.

        8) Supports DOS, Windows and OS/2 - We said earlier that 386 systems
do not support an on chip cache as found in the Upgrade Microprocessor. In
order to turn on the cache a small program is automatically run when booting
up the PC when the upgrade installed. This program is included with the
upgrade package on 3.5" and 5.25" diskettes along with easy to follow steps
for installing the software onto your hard drive while running either DOS,
OS/2 or Windows. The cache software will run each time the computer is booted an
d since it simply turns the cache on it does not stay
resident. It does not interfere with any operating system functions or
applications the user will be running.



        10) Easy Installation - Since the Cyrix 386 to 486 Upgrade Micro-
processor solution is a single chip and there are no BIOS or other system
modifications needed, installation is easy and straight forward. Installing
the upgrade requires three steps: 1) Remove the 386DX microprocessor,
2) Insert the Cyrix Cx486DRx2 processor into the microprocessor socket and
3) Install the cache software.


         Difference between a 386 and a 486 Computers

        The viability of upgrading a 386 computer to a 486 by using the
Upgrade Microprocessor can best be understood if we take a look at the real
differences between the two types of systems:

COMPONENT               386 COMPUTER            486 COMPUTER
Microprocessor          386DX/SX                486DX/SX
>>>>>>>>>>              Supports 386            Supports 486
>>>>>>>>>>              Instruction Set         Instruction Set


Graphics                VGA Standard            VGA Standard
>>>>>>>>>>              Super VGA Available     Super VGA Available


Disk Drive              IDE Interface            IDE Interface
>>>>>>>>>>              Multiple Drives          Multiple Drives


Memory                  SIMM Device              SIMM Device
>>>>>>>>>>              Expandable to 12MB       Expandable to 16MB



        From the above chart we can see that both 386 and 486 computers
use VGA as the graphics standard, expandable SIMM memory, and an IDE drive
interface supporting multiple drives. The major difference is the micro-
processor.

        In the past, as each new generation of processor became available
the only path for taking advantage of new processor technology was to pur-
chase a new computer. This was true because of the major differences between
8088, 286 and 386 systems in terms of design, graphics, memory and disk
interfaces.

        The key point with Cyrix's Cx486DRx2 Upgrade Microprocessor is that
it upgrades the main difference between a 386 and 486 computer; the micro-
processor.

       Compatibility

        The Cyrix Upgrade Microprocessor has been tested in numerous PCs for
compatibility including systems from IBM, Compaq, AST, Everex, Dell and
Toshiba. There have been only a few systems that have not tested compatible.



The following systems have exhibited an incompatibility with Upgrade
Microprocessor:

        - Sun i386 systems
        - Memorex 386 systems

        The IBM PS/2 Model 70/16MHz has tested compatible but the Upgrade
Microprocessor requires the system to have 85ns memory installed. The system
originally came from IBM standard with 2MB of 85ns memory. IBM's specifi-
cation on additional memory called for 85ns memory. Unfortunately, a number
of systems upgraded beyond the initial 2MB were upgrade with slower 100ns
memory. Although this generally does not cause problems in the Model 70,
when upgrading to a faster microprocessor the system will need all memory
to be 85ns. This requirement only affects the 16MHz model.

        A small number of the early Compaq Deskpro 386/16MHz came with a
287 math coprocessor socket instead of the standard 386 math coprocessor.
Installation of the Upgrade Microprocessor will require the removal of any
287 math coprocessor installed in the system.



       Packaging

        The Cyrix Upgrade Microprocessor comes in a single package containing th
e
following items:

                        * Cx486DRx2 microprocessor chip
                        * Installation Manual
                        * Pair of 386DX microprocessor removal tools
                        * Upgrade Cache installation disks (3.5" & 5.25")
                        * Pin 1 locator arrow *
                        * Heat sink (required for 20/40 and 25/50)
                        * Warranty Registration Card

        * The pin 1 locator arrow aids in the ability of properly orienting
the Upgrade Microprocessor correctly in the socket.

