From: kegs@provalid.com   
      
   In article <10brpft$23go$1@gal.iecc.com>, John Levine   wrote:   
   >It appears that Kent Dickey  said:   
   >>>AFAIK, the main problem with SASOS is "backward compatibility", most   
   >>>importantly with `fork`.  ...   
   >   
   >>First process is ASID=1.  It forks, and the child is ASID=2.  It is a   
   >>completely new address space. ...   
      
   Sorry, bad terminology.  I just means all addresses under ASID=2 are   
   invalid.   
      
   In my example, all processes can peek inside any other process's address   
   space, by just forming the 64-bit virtual address.  The ASID thing is   
   just a convention, so I wouldn't have to type 16 digit hex numbers over and   
   over.   
      
   [snip]   
      
   >The last widely used single address space systems I can think of were OS/VS1   
   >and OS/VS2 SVS, each of which provided a single full sized address space in   
   >which they essentially ran their real memory predecessors MFT and MVT.  As   
   >Lynn has often told us, operating system bloat forced them quickly to go   
   >to MVS, an address space per process.   
      
   HP-UX on PA-RISC from 1986-2004 or so was effectively a SAS computer.  In   
   32-bit CPUs, the virtual address space was 48 bits, and normal user code could   
   form any 48-bit address, and this was used for shared libraries and shared   
   code (processes running the same executable shared the same virtual address   
   space for the executable).  In 64-bit mode, it works mostly as I described.   
   There were 32-bit Space registers which were OR'ed into the upper bits of   
   the 64-bit virtual address, to give the global 64-bit system address.   
   It was an OS convention to limit the Space values to the upper 16 bits or so,   
   and it could change it to whatever it wanted.   
      
   >I suppose there could still be single address space realtime or   
   >embedded systems where all the programs to be run are known when the   
   >system is built.   
   >   
   >   
   >   
   >--   
   >Regards,   
   >John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for   
   Dummies",   
   >Please consider the environment before reading this e-mail. https://jl.ly   
      
   Kent   
      
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