[cctalk] Re: Vintage Computer Fest Midwest "DECnut" pizza party

[Paul Koning via cctalk]

> On Sep 7, 2023, at 9:12 AM, Paul Koning via cctalk <cctalk@classiccmp.org> 
> wrote:
> 
> 
> 
>> On Sep 7, 2023, at 3:17 AM, Lars Brinkhoff <l...@nocrew.org> wrote:
>> 
>> Paul Koning wrote:
>>> Even then it increments by 2, by special exception.  So 112700, 1
>>> (movb #1,r0) fetches the instruction and increments PC by 2, then
>>> fetches the word where the PC points and increments by 2, not 1,
>>> again.
>> 
>> It's not really a special exception because immediate mode is @(R7)+.
> 
> (R7)+, actually; @(R7)+ is absolute.  I meant "special exception" because 
> auto inc/dec of R6 and R7 always increments by 1, while for R0-R5 it 
> increments by the datum size.

Oops, typo.  Of course, auto inc/dec of R6 and R7 (SP and PC) always increment 
by TWO, while auto inc/dec of other registers increments by the size of 
whatever is accessed.

        paul