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PC 80486

Juan P. Abonia pablo at acsu.buffalo.edu
Mon Jan 25 14:07:09 EST 1993

In article <1993Jan25.170138.10928 at welchgate.welch.jhu.edu> ken at oscar.welch.jhu.edu (Ken Fasman) writes:
>In article <1993Jan25.090410.12066 at gserv1.dl.ac.uk>, schnorr at tournesol.versailles.inra.fr (Kirk Schnorr) writes:
>|> 	We were thinking to get a 486SX based machine since it is the
>|> cheapest but I do not want to sacrifice a built in  math co-proccessor
>|> or 32 bit data path it the 486SX is missing these.  Can anyone enlighten
>|> me?
>My understanding of the various members of the Intel 80386 and 80486 families 
>are as follows:
>Chip		Internal	External	Floating
>Designation	Data Path	Data Path	Point Unit?
>-----------	---------	---------	-----------
>386DX		32 bits		32 bits		No
>386SX		32 bits		16 bits		No
>486DX		32 bits		32 bits		Yes
>486SX		32 bits		16 bits		Yes
>Please note that Intel uses the "SX" designation to denote the narrower 
>external data path, NOT the presence or absence of a math coprocessor.

This isn't always true.  The 486SX has a disabled floating point unit.  The
upgrade chips (Overdrive) for these machines disable the original CPU when they
are installed (They have an enabled FPU).  I believe that the 486SX retains a
32-bit external data path.
J. Pablo Abonia
University at Buffalo				 BITNET:    pablo at sunybcs.BITNET
Roswell Park Cancer Institute			 Internet:  pablo at cs.Buffalo.EDU

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