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ARM, like other RISC architectures MIPS and PowerPC, has a fixed instruction size of 32 bits. This is a good design decision So good that they got rid of it in
by gcp 9y ago
ARM, like other RISC architectures MIPS and PowerPC, has a fixed instruction size of 32 bits. This is a good design decision
So good that they got rid of it in their new chips.
- deleted 9y ago[deleted]
- Parcissons 9y agoSo good that they offer the alternative called thumbcode.
- renox 9y agoYep all these ISA have a 16bit extension.
- cesarb 9y agoExcept, for some reason, ARM's new 64-bit ISA, which has 32-bit instructions only. I wonder how long before they release a "Thumb-64" extension...
- pcwalton 9y agoI doubt it'll be as easy as it was for 32-bit ARM because AArch64 has no (well, only a few) predicated instructions. Instead, the 64-bit ISA effectively uses those bits to name additional registers. AArch64 already has similar code density to x86-64 anyway.
- pcwalton 9y agoAArch64's ISA has only 32-bit instructions.
- simias 9y agoCan you explicit what you mean by that? Are you talking about Thumb? Although that's not exactly "new" I suppose.