From: jl@glen--canyon.com   
      
   On Fri, 13 Feb 2026 00:38:43 +0100, Gerhard Hoffmann    
   wrote:   
      
   >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.   
      
   I called it stack oriented!   
      
   A couple of people made real stack machines, hyper-CISC things with   
   advanced instructions. HP and Intel as I recall. They were pig slow   
   and didn't last.   
      
   >   
   >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   
   >   
   >   
      
   On the PDP-11 there was a short program to fill every location in   
   memory with zero, the halt opcode.   
      
   And another program would fill all of memory with the NOP opcode, and   
   it would cycle on that forever.   
      
      
   John Larkin   
   Highland Tech Glen Canyon Design Center   
   Lunatic Fringe Electronics   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)