17 Sep
2016
17 Sep
'16
12:05 p.m.
Op 17 sep. 2016 8:34 p.m. schreef "Guy Sotomayor Jr" <ggs at
shiresoft.com>:
internal
On Sep 17, 2016, at 10:10 AM, Chuck Guzis
<cclist at sydex.com> wrote:
On 09/17/2016 09:23 AM, Eric Smith wrote:
Why? What does the width of the ALU have to do with the ?bitness? of the
architecture? If the programmer?s view is 8-bits (or 16 or 23, or ??),
what does it matter (other than performance) what the width of the I don't know what the width of the TMS9900
ALU is, but I'm pretty
sure it's not bit-serial, as an add instruction only takes 14 clock
cycles, including four memory cycles. I'd be very surprised if the
ALU isn't either 8 or 16 bits, though 4 might be possible.
Possibly someone is confused by the bit-serial "CRU' I/O space, but
that is unrelated to the ALU width.
Could very well be--I'm just going by other's appraisals of the
architecture.
But there were some "8 bit" MPUs with bit-serial ALUs, so the question
is still valid.
data paths or ALU are?
It?s interesting from an implementation point of view but not really
anything else.
In a previous email, I mentioned the IBM 360 as an example of a 32-bit
machine
(architecture) that had 8, 16 and 32 bit internal data
paths and I don?t
think
anyone would suggest that the 360 models that did not
have 32-bit data
paths
wasn?t a 32-bit ?machine?.
Don't forget about the 64-bit implementations, like the model 65.
The same could be said for the PDP-8/s. That?s a bit serial machine but
it
is a member of the PDP-8 family. Would you call it a
1-bit machine or a
12-bit
machine?
That?s why (in my previous email) I made the distinction between
architecture
and implementation. The reference ?machine? (which
I?ve intentionally
used here)
is somewhat ambiguous and I tend to use architecture
or implementation
when I
want to be specific.
TTFN - Guy