                      How To Upgrade Your 486 CPU
             By Don Pellegrino (don.pellegrino@dewdrop.com)

    If you need more speed for math, complex processing, or just need
better  performance overall, you should consider upgrading your Central
Processing Unit (CPU). Because of the significance and complexity of
your CPU, you must consider many factors when upgrading. Brand name,
speed, compatibility, and price must all be taken into account. Because
of the variety of motherboards and processors out there, this article
has been specifically written in the interest of the 80486 user.

PRICE IS ALWAYS THERE
    When upgrading, no less than double the power is recommended. A 25
MHz to 33 MHz upgrade would not be worth the cost and trouble,
especially considering the rate at which technology is evolving. You
should look past you current needs and more at your budget. Get the best
that you can afford now and it will be cheaper and more effective in the
long run. If the applications you are running now are working at a
comfortable rate there is no reason to upgrade. Remember, "Don't fix it
if it ain't broken."  If u wait until things slow down you will be able
to take a bigger jump at a lower price. If you find yourself getting a
bite to eat between program execution a CPU upgrade is the most
effective upgrade you can perform.

GENERIC CHIPS?
    Intel, Cyrix, and AMD (Advanced Micro Devices) are the three major
producers of processors. Intel was one of the first developers of the
CPU. They had a monopoly on production until they were challenged on the
copyright of a number (80486). Since then, Cyrix and AMD have been
producing processors based on the 8086 command set. Intel however, is
the only producer of the Pentium processor.
    Intel has greater customer loyalty and their processors are
considered to be of slightly higher quality. You have probably heard the
"Intel Inside" slogan. Intel is trying to gain business through
advertisement and customer support. If you were to get a faulty CPU from
Intel you would probably have an easier time getting it replaced.
    Cyrix and AMD are just as reliable as Intel and totally compatible.
They simply don't do as much advertising. Cyrix and AMD processors are
usually twenty to thirty dollars cheaper. I recommend a Cyrix or AMD
CPU. You may need to buy a CPU fan (about eight dollars) to get the few
extra clock ticks the Intel equivalent provides, but, you will still
save money with a Cyrix or AMD.

THE NEED FOR . . .
    The speed that you upgrade to is relative to your current speed. If
you are slowing at 50 MHz an upgrade to 66 MHz is not going to make that
much of a difference. You need to be looking at DX4100 and Pentium
technology. If 25 MHz is your bottleneck then 66 MHz would be
appropriate. 33 MHz to 100 MHz would be useful as well.
    When you upgrade the CPU, don't forget about the crystal. Most
motherboards come with a removable thumbnail sized box that determines
the speed at which your video and IO will operate. A 66 MHz CPU with a
25 MHz crystal is going to run at 50 MHz. Crystals will be discussed
further in the compatibility section.
    Your 80486 motherboard will probably operate at one of the following
speeds: 25, 33, or 50 MHz. Processors come in SX, DX, DX2, and DX4
variations of those speeds. An SX extension means that the CPU comes
without a built-in coprocessor. A DX extension means that the CPU comes
with a built in math coprocessor. A DX2 is a DX that internally runs at
twice the speed. A DX4 internally runs four times faster than a DX but
the motherboard and IO still run at DX speed. A DX4100 will calculate at
100 MHz but and BUS access will still operate 25 MHz.

CAN THEY TALK?
    Most 486 and all Pentium motherboards come equipped with a ZIF (Zero
Insertion Force) socket. The ZIF allows you to remove the current CPU,
whereas the earlier systems came with the CPU soldered into the
motherboard. You must have a ZIF socket to upgrade your CPU.
    Your new CPU may or may not be compatible with your current
motherboard. Compatibility is usually determined by the crystal
installed. Every motherboard uses a crystal, either soldered in, like
most Tandy computers, or removable, as in most systems. If your crystal
is soldered in, you can only upgrade to a processor that is compatible
with that crystal. A motherboard with a 50 MHz crystal cannot be
upgraded without changing the crystal. A new crystal of any speed will
cost around ten dollars and is probably available from the same dealer
who sold the CPU.

WHERE TO TURN
    This article was written to advise on upgrading a 486 CPU. It was
written in an easy to understand manner that will give you all of the
information you should need to decide on an upgrade. No less than an
encyclopedia sized document could present enough information to cover
the entire spectrum of technology surrounding the microprocessor. If you
would like more information on microprocessors, you should give Intel's
Fax Back service a try. The number is 18005253019. Intel Customer
Support could also y useful (18005383373). Don't stop there however,
book stores, libraries, and on-line resources also abound with
information on this topic.

