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> In fact, many would argue it's fair to say that ARM is not RISC It isn't now... ;-) It's interesting to look at how close old ARM2/ARM3 code was to 6502 mac
by ErroneousBosh 1y ago
> In fact, many would argue it's fair to say that ARM is not RISC
It isn't now... ;-)
It's interesting to look at how close old ARM2/ARM3 code was to 6502 machine code. It's not totally unfair to think of the original ARM chip as a 32-bit 6502 with scads of registers.
And, for fairly obvious reasons!
- Joker_vD 1y agoBut even ARM1 had some concessions to pragmatics, like push/pop many registers (with a pretty clever microcoded implementation!), shifted rigsters/rotated immediates as operands, and auto-incrementing/decrementing address registers for loads/stores. Stephen Furber has extended discussion of the trade-offs involved in those decisions in his "VLSI RISC Architecture and Organization" (and also pretty much admits that having PC as a GPR is a bad idea: hardware is noticeably complicated for rather small gains on the software side).