Reproduction micros

Lars Brinkhoff lars at
Fri Jul 22 01:34:41 CDT 2016

Liam Proven writes:
> Peter Corlett wrote:
>> In ARM, *all* instructions can be predicated. Because instructions
>> are 32 bits wide, it has the luxury of allocating four bits to select
>> from one of 16 possible predicates based on the CPU flags.
> If I understand it correctly, this caused considerable problems for
> the RISC OS people later. The original Acorn ARM machines used 26 bits
> of the program counter as the PC, and the rest as flags.
> I'm not sure this is the same phenomenon you're describing.

It's not.  Peter is talking about a four-bit field in the instructions.
You're talking about a six-bit field in the program counter.

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