From: terje.mathisen@tmsw.no   
      
   John Levine wrote:   
   > It appears that Terje Mathisen   said:   
   >> My "Algorithms and Data Structures" professor told us that IBM had   
   >> patented a zero-time sort chip, which they then promptly buried since   
   >> their internal stats said that over all IBM mainframes, 60% of the CPU   
   >> hours were spent in various forms of sorting.   
   >>   
   >> Terje   
   >>   
   >> PS. The chip was a ladder of comparators, so that you could use a   
   >> channel to stream data into it, then when you were done (or the chip was   
   >> full) you would run the channel transfer in the opposite direction to   
   >> retrieve the sorted data.   
   >   
   > Sounds like an urban legend to me.  For one thing, on machines of that   
   > era no useful sort fit in core so it spent most of its time doing disk   
   > and tape I/O anyway.   
      
   Professor Halaas (he had written the textbook we used and later on got   
   FAST to actually produce a search chip) quoted an actual patent number   
   afair.   
      
   And that was probably the main (but not only!) reason for not actually   
   creating the hardware. Besides, patents were already a way to gain   
   bonuses/salary increases, right?   
   >   
   > For another, if it really did make a difference, they would have   
   > called it the Improved Sort Performance Facility and sold it as an   
   > extra cost option.   
   >   
   > These days z/Series has the optional Enhanced-Sort Facility added in   
   > September 2020 which adds a complex SORT LISTS instruction that does   
   > in-memory sorts or merges presuably in microcode so it can run at full   
   > memory speed.   
      
      
   As soon as a sort is large enough that it needs to start in physical RAM   
   and also end up there, the best you can do is to minimize the number of   
   cache and TLB misses: The actual branch misses probably don't matter?   
      
   Terje   
      
   --   
   -    
   "almost all programming can be viewed as an exercise in caching"   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)