10 Jul
2024
10 Jul
'24
8:20 a.m.
In order to port VMS to new architectures, DEC/HP/VSI
...
turned the VAX MACRO assembly language (in which
some of the VMS operating system was written) into a
portable implementation language by 'compiling' the
high-level CISC VAX instructions (and addressing modes)
into sequences of RISC instructions.
Clem Pease did the same thing to port TMG from IBM 7000-series machines to
the GE 600 series for Multics, circa 1967. Although both architectures had
36-bit words, it was a challenge to adequately emulate IBM's accumulator,
which supported 38-bit sign-magnitude addition, 37-bit twos-complement and
36-bit ones-complement.
Doug