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As a former microarchitect, the contortions designs take on is due to a combination of factors, usually stemming from routing/timing problems in the design or b

As a former microarchitect, the contortions designs take on is due to a combination of factors, usually stemming from routing/timing problems in the design or backwards compatibility, and every now and then, compiler team requests. For example, endian-ness looks like weirdness to a programmer, but not to a chip designer that needs to read in lower-order bytes first to decode an instruction quickly. Why not just change the instruction decoder? Because it needs to be backwards compatible to what was once a byte-sized ISA. But for programmers who don't understand the history, it seems insane.

Annatar 4y ago
That's because it is insane: how come most processors are big endian, how did they manage just fine?
- gotaquestion 4y ago
  First off, most processors are not BE. Arm and X86 are LE and cover "most processors". Second, processors like the Motorola 68000 were 32-bit, so there was no need to read just the first byte. Refer to my point about instruction fetch. Like I said, if you have an ISA that came from byte-sized opcodes, and then expanded later, you need to fetch bytes first. However, if your opcodes are 32-bit, then the code is bigger. (In the old days, CISC code size was a selling point compared to RISC, this opcode compression was one of the reasons.) This is what you learn in first-year computer architecture. However the world has changed a lot since the 80's. Single bytes aren't fetched in x86, 256-byte cachelines are, and the decode happens on that.
  - Annatar 4y ago
    ARM and x86 are only two out of many processors: you are purposely choosing to confuse market dominance with what exists, and I fault you for it, because by behaving in this way, you are helping perpetuate the monoculture. The moment you help perpetuate a monoculture rather than subvert it and fight it at every turn and opportunity, you become part of the problem.

Annatar 4y ago

That's because it is insane: how come most processors are big endian, how did they manage just fine?

gotaquestion 4y ago
First off, most processors are not BE. Arm and X86 are LE and cover "most processors". Second, processors like the Motorola 68000 were 32-bit, so there was no need to read just the first byte. Refer to my point about instruction fetch. Like I said, if you have an ISA that came from byte-sized opcodes, and then expanded later, you need to fetch bytes first. However, if your opcodes are 32-bit, then the code is bigger. (In the old days, CISC code size was a selling point compared to RISC, this opcode compression was one of the reasons.) This is what you learn in first-year computer architecture. However the world has changed a lot since the 80's. Single bytes aren't fetched in x86, 256-byte cachelines are, and the decode happens on that.
- Annatar 4y ago
  ARM and x86 are only two out of many processors: you are purposely choosing to confuse market dominance with what exists, and I fault you for it, because by behaving in this way, you are helping perpetuate the monoculture. The moment you help perpetuate a monoculture rather than subvert it and fight it at every turn and opportunity, you become part of the problem.