8038x > IntelRAPIDCAD-1
Modified: April 18, 2005, 5:24 pm
Manufacturer:Intel
Model:RAPIDCAD-1
Speed:33MHz Max
Type:80486
Data Code:9215
Introduced:1991
Transistors:800,000
Package:132CPGA
Process:0.8 Micron
Architecture:32 bit
Used in:80386 Systems
Description:The RapidCAD is not a coprocessor, strictly seen,
although it was marketed as one. Rather, it is a
full replacement for a 80386 CPU: basically, an
Intel 486DX CPU chip without the internal cache
and with a standard 386 pinout. RapidCAD is
delivered as a set of two chips. RapidCAD-1 (S-
Spec: SZ624) goes into the 386 socket and
contains the CPU and FPU. RapidCAD-2 (S-Spec:
SZ625) goes into the coprocessor (387) socket and
contains a simple PAL(Programmable Array of
Logic) whose only purpose is to generate the FERR
signal normally generated by a coprocessor (This
is needed by the motherboard circuitry to provide
287 compatible coprocessor exception handling in
386/387 systems.) The RapidCAD instruction set is
compatible with the 386, so it doesn't have any
newer, 486-specific instructions like BSWAP.
However, since the RapidCAD CPU core is very
similar to 80486 CPU core, most of the register-
to-register instructions execute in the same
number of clock cycles as on the 486.

http://www.cpushack.net/RAPIDCAD.html