• Why in A64 the coprocessor is removed?
    For the view of architecture, why the coprocessor is removed for A64 instruction set?
  • ARM MUL instruction
    Still more instruction things giving me head ache. This time it's the MUL-instruction. What the heck means: Multiply multiplies two register values. The least significant 32 bits of the result are written...
  • Register 'names' in instruction descriptions
    The registers in the instructions are usually 'named' Rn, Rm, Rd, ... Is there some deeper meaning in the names? Usually Rd seems to mean 'destination register' Sometimes Rn is the only operand, sometimes...
  • UNPREDICTABLE in instruction description (Lord! yet another question)
    In quite many instruction descriptions it says: if d == 15 then UNPREDICTABLE; What does this mean? Can the instruction really work in some unexpected way in each such case or what? I guess if I use...
  • Bit 22 in some LD/ST instructions (Cortex-A7)
    I wonder if the bit 22 has some function in instructions like LDRH, STRH, LDRSBT, LDRD, ... (bits 27, 26, 25 = 0, 0, 0)?                            22 c c c c 0 0 0  0  U 1  1  0 n n n n t t t t x x x...