10 Apr
2002
10 Apr
'02
4:19 p.m.
Allison wrote:
some items sorta conspired to drive cpus to multiples of 8bits.
ASCII chars
width of data paths internal to MOS cpus early on.
byte wide memories, especially rom/prom/eprom
Personally I like either 18 ot 24 bits and have thought that
the PDP-8 with the right side (address portion) of the word
stretched to 18 bits or better yet 24 would be a nice machine.
here is a nice 17?
bit computer of that era
http://www.xpuppy.demon.co.uk/molecular.htm
24bits is majik as it's a multiple of 8.
PDP-8 addressing as 24bit 524288 word page, current and
also there is page 0 addressing! A field would be
16MB. EMA would not be needed.
The one feature the PDP-8 and most other machines of that vintage (pre
1970) is the idea of a stack pointer for stacks and local variables.
That is one reason C never really took off on 8 bit micros because
local variable addressing was so clumsy. The 8086 did have base
addressing and that saved it from being a failure as far as high level
languages are concerned.
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html