From: muta...@gmail.com   
      
   On Monday, July 12, 2021 at 11:30:40 AM UTC+10, muta...@gmail.com wrote:   
      
   > 24-bit addressing, and a theoretical x86 processor with   
   > 32-bit addressing. Come to think of it, it might be possible   
   > to use an actual 80386 to do effective 16-bit segment   
   > shifts. Or surely I can at least match the 80286 and do   
   > (effective) 8-bit shifts. That would be a load of fun.   
   > I guess it depends how many selectors I can define on   
   > the 80386. I'll run everything in supervisor mode, so I   
   > can use both GDT and LDT if that helps.   
      
   I looked up Wikipedia:   
      
   https://en.wikipedia.org/wiki/Global_Descriptor_Table   
      
   and there are 8192*2 selectors available, meaning that   
   16-bit programs can access 1 GiB maximum.   
      
   4-bit segment shifts make sense when there is 1 MiB of   
   memory available.   
      
   5-bit when there is 2 MiB.   
      
   6-bit when there is 4 MiB.   
      
   So the pattern is:   
      
   C:\devel\bochs>zcalc 65536*2**14/1024/1024   
   Calculated Value is 1024.000000   
   Thank you for using the calculator   
      
   13 bit shifts are the last purposeful one, to give 512 MiB,   
   and after that, you may as well just use 16 bit shifts.   
      
   Given the restrictions of the 80386.   
      
   BFN. Paul.   
      
   --- SoupGate-Win32 v1.05   
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