From: muta...@gmail.com   
      
   On Thursday, October 13, 2022 at 10:09:52 AM UTC+8, Joe Monk wrote:   
   > > On a modern CPU, what happened to real mode programs   
   > > was not that they had performance problems, but that   
   > > they simply stopped working one day with 64 bit   
   > > operating systems, plus they were permanently   
   > > constrained to 1 MB. I don't know what the 64 bit   
   > > issue was, and I don't really care at the moment.   
   > > I'm just interested in why there ever needed to   
   > > be a 1 MB limit - the answer is, there didn't.   
      
   > The reason for the 1MB limit is a physical one. The largest chip   
   > at the time was a 40-pin DIP. Subtracting 20 address pins only   
   > leaves 20 other pins for CPU control signals.   
      
   My question above was for a modern CPU.   
      
   I don't care that the 8086 was restricted to 20 bits.   
      
   What I care about is that in the 1990s I was running DOS   
   on an 80386+ with 16+ MB of memory, and hitting memory   
   constraints of 1 MB.   
      
   I don't know why everyone here is reluctant to question   
   Microsoft/Gates/Paterson.   
      
   The correct answer, as far as I can tell, is that these people   
   did not see a problem with hardcoding the number 4.   
      
   At the very minimum they should have allowed that number   
   to change to anything up to 16, to cater for future processors.   
      
   Ideally they should have allowed a flexible segment manipulation   
   for completely different processors (namely the switch to   
   selectors).   
      
   In actual fact, DRDOS should have done it if Microsoft was   
   unwilling to.   
      
   Regardless, I can lift that limit on PDOS/86, and I can even   
   exercise it on a real processor - PM16 and PM32 with the   
   D-bit set appropriately.   
      
   And I can do it in RM16 with a modified Bochs.   
      
   BFN. Paul.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)