From: muta...@gmail.com   
      
   On Tuesday, August 30, 2022 at 9:06:35 PM UTC+8, Scott Lurndal wrote:   
   > "muta...@gmail.com"  writes:   
   > >On Tuesday, August 30, 2022 at 7:19:44 AM UTC+8, Scott Lurndal wrote:   
   >   
   > >> >What would you recommend within the   
   > >> >constraints of late 70s hardware and my   
   > >> >desire for a flexible shift value, not   
   > >> >necessarily immediately, but with a new   
   > >> >8086-5+ to be released in the mid 80s.   
   > >> I'd recommend you look at the Motorola 68000.   
   > >   
   > >No, that's not what I'm after.   
   > >   
   > >Ok, what if the 5 bit segment shift option was   
   > >to be added to the 80286 or 80386 instead?   
   > >Would that be a minor addition?   
   > There is no such thing as a minor addition (no pun intended)   
   > when adding features to a processor chip.   
   > >   
   > >And maybe for the 8086 have an instruction that just   
   > >loads the number 4 into ax? Would that be a minor cost?   
   > The 8086 already has an instruction that loads the number 4   
   > into AX (MOV AX,4 / mov $4,%ax).   
   >   
   > There is no such thing as a minor change when designing   
   > and implementing a CPU. Consider the effect on the   
   > instruction decoder alone; if it uses a VLIW-style   
   > implemention, a new ROM will need to be developed and   
   > tested for the entire supported feature set (instructions   
   > and corresponding semantics), if it uses straight logic,   
   > the entire logic tree needs to be redesigned, laid out   
   > (by pen and ink in those days), and reimplemented.   
   >   
   > Like I noted earlier, anything is possible given enough   
   > time and money.   
      
   I don't know if you genuinely don't understand my   
   proposal, but it is only on the 8086 that the   
   instruction would simply put 4 into ax or ah or al.   
      
   On other processors, not necessarily built by   
   Intel, the instruction would return anything from   
   4 to 16.   
      
   --- SoupGate-Win32 v1.05   
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