22 Apr
2024
22 Apr
'24
9:18 a.m.
On 4/22/24 08:36, Lamar Owen via cctalk wrote:
Die real estate forced the design to do without a full
8-bit ALU. When
you have a 4-bit ALU, and you are doing 16-bit math, you will need 4
cycles through the ALU.
I don't know if this applies to the Z80, but on the 8080, 16-bit
increment/decrement is handled by a separate increment block (also used
to advance the P-counter and stack operations). Probably one of the
reasons that INX/DCX doesn't set any flags.
--Chuck