7 May
2025
7 May
'25
11:59 p.m.
On Wednesday, May 7, 2025 at 20:37, Holm Tiffe via cctalk wrote:
Dave a Z80 has an 4 Bit ALU, but isn't essentially
a 4-bit processor.
I'm not familiar with the Z80 internals. However, the 2200 theory of
operation manual states, "The eight 4-bit File Registers are used as
general purpose registers during arithmetic computations and related
calculator processing." Also, "When data is written into memory, only four
bits from the data bus can be written at a time." Also, the immediate
machine instructions supply only 4-bit operand values. These plus the
presence of decimal instructions seem suggestive to me that the machine is
designed to process digit-serial BCD numbers.
-- Dave