16 Sep
2016
16 Sep
'16
3:20 p.m.
I wrote:
The 68000 has three separate 16 bit ALUs: one for
DataLow, one for
AddressLow and another for AdressHigh. DataHigh can be processed by
either the first or the second one. The first one implements all
operations while the other two only do add/subtract and some limited
shifting.
See figure 8 of:
https://www.computer.org/csdl/mags/co/1979/02/01658617.pdf
Ooops- my explanation got the last two ALUs backwards. DataHigh and
AddressHigh share an ALU.
Note that in the conclusion to this 1979 article, the Motorola engineers
say "It is a 32-bit architecture that supports many data types and data
addresses."
- Jecel.