From: gneuner2@comcast.net   
      
   On Tue, 5 Aug 2025 05:48:16 -0000 (UTC), Thomas Koenig   
    wrote:   
      
   >Waldek Hebisch  schrieb:   
   >> I am not sure what technolgy they used   
   >> for register file.  For me most likely is fast RAM, but that   
   >> normally would give 1 R/W port.   
   >   
   >They used fast SRAM and had three copies of their registers,   
   >for 2R1W.   
      
      
   I did use 11/780, 8600, and briefly even MicroVax - but I'm primarily   
   a software person, so please forgive this stupid question.   
      
      
   Why three copies?   
   Also did you mean 3 total? Or 3 additional copies (4 total)?   
      
      
   Given 1 R/W port each I can see needing a pair to handle cases where   
   destination is also a source (including autoincrement modes).  But I   
   don't see a need ever to sync them - you just keep track of which was   
   updated most recently, read that one and - if applicable - write the   
   other and toggle.   
      
   Since (at least) the early models evaluated operands sequentially,   
   there doesn't seem to be a need for more.  Later models had some   
   semblance of pipeline, but it seems that if the /same/ value was   
   needed multiple times, it could be routed internally to all users   
   without requiring additional reads of the source.   
      
   Or do I completely misunderstand? [Definitely possible.]   
      
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