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Intel's 386?
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It is normal practice in the electronics industry to share
the design of a chip with another manufacturer so that it can be 'second
source'. The argument goes that second sourcing induces confidence that the
product has a life beyond the original designer. Intel second sourced the 286
but with the 386,486 and beyond Intel has decided to keep its design to if self
by not signing second sourcing deals and by threatening to stop any
manufacturer from infringing its patents and copyrights.
For some time this gave Intel a total monopoly on the
386/486 market and resulted in higher prices. Other manufacturers had to work
hard to construct their own 386 designs from scratch but eventually they did.
The availability of 386 chips from sources other than Intel had to two effects.
The first is that the price of the 386
fell rapidly and the second is that Intel shifted its emphasis onto
creating special purpose and enhanced
versions of the 386 and 486 for which other manufacturers had no equivalents.
Some of the marketing ploys used by Intel are bound to
confuse and puzzle the onlooker unless they are seen in the context of trying
to keep customers loyal to Intel. For example, the 486SX is a lower
specification 486DX but Intel only introduced it as a way of drawing customers
away from the newly introduced lower cost 386DX chips produced by other
manufacturers. In fact the early 486SX chips were simply full 486 chips with
the numeric co-processor section disabled! The 486SX quickly settled down to
look more like a respectable member of the family but the fact still remains
that Intel wouldn't have produced it if
there had been no competition. Another interesting twist in the 486SX story is
that in order to add a numeric co-processor, the chip that you install next to
it, the 487SX,is actually a full 486DX processor! In this situation the
original 486SX sits in its socket doing nothing much at all.
In an affords to turn the 'empty socket' next to the 486SX
into a marketing advantage, Intel invented the idea of offering users an
upgrade chip which they could fit in place of the 487SX to boost performance
still further. The increased performance is achieved by a technique called
'clock doubling'. This is explained In more detail in the next chapter but
essentially it succeeds in doubling the rate at which the processor works
without the need to make any changes to other parts of the machine. This is such a good idea that Intel extended it to
the other members of the 386 family so, for example, you can now buy the 486DX2
which is identical to the 486DX but runs twice as fast.
Intel's competitors are also producing new and improved
versions of the 386 family. There are already faster 386DX and 386SX chips from
sources other than Intel. At the time of writing the first non-Intel 486 chips
have arrived on the market. There are also likely to be some interesting innovations. For example, the chip
manufacturing company calyx has just announced the 486SLC which is a 486-like
processor that can be used to replace a 386SX with a claimed 20% to 40% speed
improvement. Of course many of these
innovations are being challenged by Intel as patent infringements and there are
many law suits pending.
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