


              ################  #####      ###         #
              ##     ##     ##    # ##      #         ###
              #      ##      #    #  ##     #        #####
                     ##           #   ##    #       #   ###
                     ##           #    ##   #      #     ###
                     ##           #     ##  #     ###########
                     ##           #      ## #    #         ###
                    ####          #       ###   #           ###
                   ######        ###       ##  ###         #####

   ------------------------------------------------------------------
   |                                                                |
   |                  Technical News Association                    |
   |                                                                |
   |                               #1                               |
   |                                                                |
   |              The 486 Chips and How The Stack Up                |
   |                                                                |
   |                          Skyewalker                            |
   ------------------------------------------------------------------
 

     Just take one look in any of the latest issues of good
computer magazines, and they all say the same thing, "The 386
is dead" For the most part they are right, seeing as you can
buy 486 computer systems for under $1000 now, it hardly seems
practical to go for a 386 system anymore. Looking through the
same computer magazines, you will also see many different
types of chips, that all have the same three digits, 486.
This article will make an attempt to make some sense out of
the many different types of 486 chips, it in no means is
meant to be a technical reference.

     The first thing to notice about the new line of chips is
what comes after the numbers 486! Such letters as SX, DX,
DX2, SLC, and DLC to name a few. The list below show many of
the popular chips in the 486 line.

     Intel           Cyrix          IBM

  486SX-16       486SLC-20    486SLC2-20
  486SX-20       486SLC-25
  486SX-25       486DLC-25
  486SX-33       486DLC-33
  486DX-33       486DLC-40
  486DX-50
  486DX2-50
  486DX2-66
  Overdrive


     As you can see, there are many chips to choose from, and
the above list is not complete. Each has it's own different
features, the following is a description of each type of chip
in the 486 line in order of speed and company.



                            Intel


486SX - This is the bottom of the line, of Intel chips,
coming in 16, 20, 25, and 33 mhz version's, it caused quite a
bit of confusion among people when first released. The term
SX has changed a lot since it's inception in the 386 line,
while the 386SX had a 32bit architecture, it had a 16bit bus,
thus making it cheaper for low end computer models. This is
not so in the 486SX, it has a full 32bit architecture, and an
optimized instruction set, complete with 8k of internal
cache. What makes it different from the DX is that it's math
co-processor has either been permanently disabled, or is
simply not present at all.
486DX - This chip is what's known as a "full" 486 chip, it
has a full 32bit architecture, 8k of internal cache, and a
math co-processor built in, making faster overall than the SX
model. This chip now comes in 33, and 50 mhz versions.

486DX2 - This type of chip has a lot of misconceptions
surrounding it. The DX2 uses a phrase called "clock doubler
technology" which, as it states, doubles the internal clock
speed, the chip runs just like a 486DX-33 (486DX-66 mhz
version) except for it's internal 66mhz processing, but of
course is faster overall than a 486DX-33 because of it's raw
calculation speed, and boosting such things as DOS video
operations, the chip is available in 50 and 66 mhz versions.

Overdrive - This is a chip in the 486 line that has seen much
attention, and quite a lot of adds on the television. This is
Intel's answer to the never-ending need to upgrade your
computer. Take a look on all but the first ever 486
motherboards, and you'll notice an empty socket. This socket
is sometimes known as a "vacancy" socket. It's meant to
accept an Intel Overdrive. What an Overdrive does is plugs
into a 486SX Motherboard, and turns a 486SX-25 into a 486DX2-
50 (slightly slower than a DX2-50) and is now also available
for 486DX's to turn a 486DX-25 into a 486DX2-50, and a 486DX-
33 into a 486DX2-66. It uses "clock doubler technology" (as
explained above) and fits into a 487SX co-processor socket.


                            Cyrix

486SLC - This chip still has many people wondering if it
should be called a 486, or just a faster 386. In essence it
is simply a pin compatible replacement for a 386SX. And like
the 386SX it has only a 16bit bus, while keeping the internal
32bit architecture. The chip also has only 1k of internal
cache, and no math co-processor. The lack of an internal math
co-processor is in fact rumored to be a way of getting
around any patents by Intel on the 486 line. Instead Cyrix
bundles a Cx87DLC math co-processor with many of it's SLC's,
which improves performance. The SLC comes in 20 and 25 mhz
versions.

486DLC - This chip is made to compete with the Intel 486DX
line of chips. It still comes with only 1k of internal cache,
but like all DX's has a full 32bit architecture, that is
capable of addressing up to 4 gigabytes of RAM. The 1k of
internal cache may seem to be not enough, but as Cyrix points
out, most 486 motherboards come with at least 64k of onboard
cache, making the need for on chip cache neglagable. This
chip comes in 25, 33 and 40 mhz versions.




                             IBM


486SLC2 - This chip is meant for the portable computer
market.  It handles most things an Intel 486SX-25 would do.
The IBM SLC2 has the largest internal cache of any chip in
the 486 line so far, at 16k. The lack of an internal math co-
processor and only a 16bit bus (like a 386SX) makes it cheap,
and small, thus perfect for notebook type computers. The chip
also has "clock doubler technology" running internally at
40 mhz, while running at 20 mhz externally.


     The above list was an example of most chips in the 486
line. But because new chips are coming out all the time, many
more will probably be available as you are reading this.


                         What To Buy

     Now that you've seen the mess of chips available, it may
be slightly confusing as to which chip would suit your needs,
the following list may help you out in your decision.



Type Of Computing You Do                     Chip Recommended

General Purpose DOS Based                    486DLC-25
                                             486SX-25
                                             486SLC

DOS Based Graphics Or                        486DLC-25
Spreadsheet Work                             486DLC-33
                                             486DX2-50

Windows Environment For                      486DLC-33
Generic Applications                         486DLC-40
                                             486DX-33

Windows Environment For                      486DLC-40
Desktop Publishing                           486DX-33
                                             486DX2-66

Windows Environment For Intense              486DX-50
Graphics, or CAD/CAM                         486DX2-66

OS/2 Or Unix In A Stand Alone                486DLC-40
Configuration (High End)                     486DX-33
                                             486DX2-66

OS/2 Or Unix Very High End Applications      486DX-50
                                             486DX2-66

     The 486 chip you choose will defiantly depend on the
types of applications you choose to work with, and what you
want to get out of your computer. I hope this file has helped
in some way for you to make a buying decision, or just
understand more about all the different 486's out there.


     The information presented in this text file was meant to
give a basic overview on the new 486 line of CPU's from
different companies. It was in no way intended to have any
"special" inside information, or technical talk, just a
strait forward explanation of CPU's. And none of the
information within can be guaranteed accurate at all.

          Skyewalker
          Skyline BBS
          908-363-3832


Credits:
Computer Shopper Dec 1992
The Internet - hardware.pc (Eric S. Raymond)
