From: dk4xp@arcor.de   
      
   Am 12.02.26 um 23:12 schrieb john larkin:   
   > On Thu, 12 Feb 2026 21:05:53 +0100, Lasse Langwadt    
   > wrote:   
   >   
   >> On 2/12/26 19:19, john larkin wrote:   
   >>> The internal stack-oriented architecture of Focal-8 inspired the cool   
   >>> PDP-11 architecture which in turn inspired the 68K.   
   >>   
   >> how did stack-oriented inspire architectures with lots of orthogonal   
   >> registers, by showing how it should not be done?   
   >>   
   >   
   > Stack-oriented inspired stack-oriented. In the PDP-11, any of the   
   > registers could be used as a stack pointer.   
      
   That does not make it stack-oriented. It had registers and nice   
   addressing modes with pre-decrement and post increment etc.   
   Nice for string handling, too.   
      
   The PDP11/40e in our group was the 1st Unix machine on this side   
   of the pond.   
      
   Stack-oriented was Burroughs(sp?) B1700 or the p-code machines like   
   UCSD or Andrew Tanenbaum's EM. I wrote a Z8000 version of the EM.   
      
   We had to do a 1 semester group project for VLSI design and I   
   persuaded the group to do a somewhat dumbed-down version of   
   Tanenbaums Experimental Machine in HP's full custom dynamic n-mos   
   process.   
      
   Unluckily, another working group donated us a large metal square   
   across all of the ALU, so testing was not needed.    :-(   
   The design rule checker had its limitations for the multi   
   project wafer.   
      
   > It could do fun things like   
   >   
   > NEG PC   
   >   
   > negate the program counter.   
   >   
   > There was the land mine opcode   
   >   
   > MOV -(PC), -(PC)   
   >   
   > (014747 octal)   
   >   
   > which copied itself one location below itself and re-executed that.   
      
   OpCodes are precious!!!   
      
      
   cheers,   Gerhard   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)