Yousuf Khan said:
Actually, those CPU's that you listed were Intel's 16-bit CPUs. All of
the 32-bit CPUs were the 386, 486, and Pentium through to
early-generation Pentium 4's. The first generation Intel 64-bit CPUs
were the late-model Pentium 4's, through to the Core series. Of course,
AMD also had a generation of 32-bit (386, 486, K5, K6, through to
Athlon) and 64-bit (Athlon 64 through to Phenom, through to all modern
processors, FX-, A-, E-series, etc.) procesosrs.
Yousuf Khan
Some - I think it was the (80)486s - were one width internally, but the
previous width externally; done to keep the package size down I think,
but also to allow use with already-developed designs using the narrower
size. They were distinguished by whether the part number ended in SX or
DX, the SX being the half-width-externally ones. These worked at
whatever it was internally, but had to fetch - and return - to/from
memory in two gulps.
It wasn't helped by the fact that the same naming distinction - SX being
the inferior one - was used for a different series ((80)306s, I think,
though I could have that the wrong way round, or it could be more
complex than that) to indicate whether the processor included the
floating point processor or not. (For the ones that didn't, it could be
added as an external device, part number ending in '87 rather than '86.)
It was also around this time that processors started to run faster
internally than externally - initially by a number on the end, e. g. a
....DX4-33 ran at 33 MHz (!) externally but 133 internally. (Later they
started to use the internal speed as part of the part number as it
looked faster.)
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