4 ms·
A shift is faster than an add.
by jonsen 2y ago
A shift is faster than an add.
- russdill 2y agoOn 6502 they are both 2 cycles. On the vast majority of processors I'm aware of, "simple" alu operarations don't vary in execution time
- kragen 2y agoOn 8086 or ARM you can get a shift "for free" with your add, although on the 8086 you have to use the LEA instruction.
- ksherlock 2y agoADC #immediate is 2 cycles, as is ASL. Are you really multiplying a constant by 3 at runtime? Probably not. ADC zp is 3 cycles. Plus 2 cycles for the CLC.
- ForOldHack 2y agoThe M68020 added a dedicated barrel shifter, which could execute much faster then the M68000.