31 Dec
2005
31 Dec
'05
12:41 p.m.
e.stiebler wrote:
What about very simple 16 bit risc ?
4 bit opcode, 4 bit destination , 4 bit source 1, 4 bit source 2 ?
That is a simple design. Still any bitslice design is a muilti-board design
so for me, a more powerful CPU is larger word length than 16 bits.
20 bits does have two advantages in hindsight. 1) Good small computer
adddress range. 2) reasonable integer size -512k...512k
For me that is next year, this year I am working on 16bit cpu
using CPLDs... 3 for the cpu and two for bus interfacing.This is my version
of a simple CPU ... 16 bit words, 64kw memory AC, IX,SP,PC as registers
and No Indirect addressing. About PDP-8/e speed. 1.6 us operate 2.4 us
memory
or jump on condition and 3.2 us for jump to subroutine, with 6800 style
bus interface.
{jcc}{index}{offset}
{op-memory}{index}{offset}