3 ms·
The 68000 has a 16 bit data bus. (I always assumed it's 16 bit internally as well? Longword unary register operations take slightly longer than their word equi
by tom_ 3y ago
The 68000 has a 16 bit data bus.
(I always assumed it's 16 bit internally as well? Longword unary register operations take slightly longer than their word equivalents, even though the instruction is the same size in both cases.)
- mikepavone 3y ago> I always assumed it's 16 bit internally as well? Correct, it's mostly 16-bit internally. Registers are 32-bit, but are split into 16-bit halves. The ALU is mostly 16-bit, but has a 32-bit shift register which is used for both shift/rotate operations and multiply/divide. There's a 32-bit adder in the "address unit" that's used for effective address calculations (including the LEA instruction), but it's much more limited than the ALU
- ebruchez 3y agoThe best part was that, no matter the size of internal or external buses, the programming model was 32-bit and extremely consistent. It was (and still is I suppose) so nice to write assembly code for it.