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Software Vault: The Gold Collection
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Software Vault - The Gold Collection (American Databankers) (1993).ISO
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PENTIUM.TXT
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1993-05-29
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Is Pentium The Only Way?
by Mike Hagerty, President
Monterey Bay Area Users Group
A number of people have asked me if it is true that the 386 is dead.
They have been told that they will not be able to function without
a 486 or even a Pentium (i.e., 586) in their computer. This is
malarky. A little history may put this into perspective. When Morse
and Ravenal first designed the 8086 for Intel, one of the major
design constraints was that it reportedly had to be more or less
"compatible" with the 8080, the 8-bit chip that was the brains
inside a CP/M system. This limitation was levied upon the designers
because Intel wanted an easy port of software onto the new chip and
to make it easy to use other chips which already worked with the
8080.
The result was a cobbled up architecture which would only support 1M
of memory, unless one resorted to strange mapping schemes. Instead
of being a nice flat address space (easy for programmers to use),
it was divided into segments. The maximum size of any segment was
64K, exactly the address space of the 8080. Programs could span
multiple segments, if care was taken, but not data structures.
Motorola took the opposite approach, essentially burning the bridge
from their earlier processors and started from scratch with the
68000 (the processor in the original Macintoshes). Unfortunately
for a lot of programmers who would have had an easier time,
Motorola was incapable of shipping the 68000 until after Intel had
captured the IBM PC design and was thus relegated to perpetual
second place.
Intel developed the 80286 to provide a number of enhancements
requested by developers. Although the 80286 was technically an
improvement over the 8086, it did not provide the flat address space
which developers really wanted. This would have required discarding
the segmented address space. It would have burnt the bridge from the
8086 and potentially opened the market to the 68000. After all, if
the new chip is incompatible with the old, it is no more difficult
to go to the competitor's chip. The 80286, was the brains inside of
the AT. Because of its strong ties to the 8086 and additional
design limitations, the 286 was described as being "brain-dead". The
time for bridge-burning had come, but Intel was playing for time.
The 386 was for Intel what the 68000 was for Motorola, a break with
the past. The 386 is capable of addressing a large amount of memory
providing programmers with a reasonable architecture. To preserve
their investment, Intel made certain that programs written for the
8086 could run on the 386. However, programs written to take
advantage of the architecture of the 386 could never run on earlier
processors.
This is why WinNT and OS/2 will never run on your old AT. The 486
merely added Intel's floating point co-processor and a little cache
to the 386 resulting in a faster chip. Unless you are doing a lot
of graphics or math, the floating point co-processor is useless. If
you do need one, a 387 can be added to any 386 system for less than
$100. Thus, the 486 provides essentially nothing but a speed-up.
The real reason why Intel is pushing the 486 is that they have very
little competition for 486 market.
There are many firms making 386s faster and all cheaper than Intel's.
The margin in the 386 market has shrunk and Intel would like us to
buy their more costly and higher-margin 486s instead. The Pentium
(586) is not presently in volume shipment and no one else has made
any. You can rest assured that they will be very pricey indeed.
So, to answer the question posed to me, "No, you do not necessarily
need a 486. A 386 will probably work just fine." The 486 is faster,
but it is not appreciably different. The 386 architecture will be
around for a long time (in computing terms, that is).