From Newsgroup: comp.arch

According to Anton Ertl <anton@mips.complang.tuwien.ac.at>:

John Levine <johnl@taugh.com> writes:

According to Anton Ertl <anton@mips.complang.tuwien.ac.at>:

quadi <quadibloc@ca.invalid> writes:
But they did not design immediate operands into the architecture. I >>>wonder why that is. It increases the instruction count by about 50%.

But they did. There's a whole set of SI format instructions, with
an immediate operand and a storage operand

Ok, one can refine my statement. S/360 does not include instructions
that correspond to IA-32 instructions like

op reg, imm

True, as you noted they added those in S/390. I think that mostly
tells us that the tradeoffs changed betwen the 1960s and the 1990s.

The goal at the time was to get the scientific users to move from the
36 bit binary word addressed 7090 series, and the commercial users to
move from the BCD character addressed 1401 which had no program
visible registers and only 2000 or 4000 characters of memory. The SI instructions make sense if you want to do what the 1401 did.
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