core Estimated learning time: 12 h

EC-10.3 ARM and RISC-V, Read Side by Side

You can compare two modern instruction sets on registers, addressing, load and store behaviour and extensions, and read the relevant part of an architecture reference manual to answer a question rather than reading all of it.

Before:S5-2. Computer Architecture and MicroprocessorsUnlocks:S5-3. Digital Signal Processing

One instruction set taught alone leaves a reader unable to tell a design decision from a law of nature. Two, read against each other, make every choice visible as a choice. These two are chosen because between them they run almost everything a graduate of this area will meet, from a sensor node to a data centre.

Work through these

  • Two instruction sets, one comparison table

    Building the table yourself, row by row, is the exercise. Register count and width, instruction length, condition handling, and how a function returns are enough rows to make the two designs distinct.

    NPTEL: ARM Based Development (IIT Madras) · Course
  • Registers, widths and the calling conventions

    Both keep a modest bank of general registers and reserve a few by convention for the stack, the return address and arguments. The reservations are agreements rather than hardware, and they differ between the two.

    NPTEL: ARM Based Development (IIT Madras) · Course
  • Load-store, and why memory is not an operand

    Both designs compute only on registers and touch memory only with explicit load and store instructions. That restriction is what makes the pipeline regular, and it is why compiled code moves values about so much.

    NPTEL: Computer Architecture (IIT Delhi) · Course
  • Addressing modes, and how few you need

    A base register plus a small constant covers most real code, with an index register for arrays. Each additional mode costs encoding space and hardware, so the number of them is a deliberate budget.

    NPTEL: Computer Architecture and Organization (IIT Kharagpur) · Course
  • Extensions, profiles and what open means for an instruction set

    Both grow by optional extensions for floating point, vectors and compressed encodings, gathered into named profiles. Open here means the specification can be implemented without a licence, not that any chip is free.

    NPTEL: ARM Based Development (IIT Madras) · Course
  • Reading the architecture reference manual

    These documents run to thousands of pages and are written to be searched rather than read. Finding one instruction's encoding, its effect on flags and its exceptions is the skill worth practising.

    NPTEL: ARM Based Development (IIT Madras) · Course

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