80186 and now AMY chip

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Fri Nov 24 21:27:57 2000

From: Eric Smith <eric_at_brouhaha.com>


>According to its designers, the ALU on the 8080 is 4 bits wide, and
>takes 2 cycles for an 8-bit add or subtract. Presumably it takes at
>least 4 cycles for a 16-bit add or subtract. The 8080 takes so many
>cycles for *anything* that it's not obvious what it does internally on
>any given cycle.


It's not. It's 8bit. the cycles are wastes on delivering status and
fetching operands. You do multiple ops for 16bit adds/subs.

What makes the 8080/z80 interesting is the acc has a intermediate
carry for BCD ops.

Allison
Received on Fri Nov 24 2000 - 21:27:57 GMT