XPost: comp.sys.sinclair, comp.sys.atari.8bit, comp.sys.apple2   
   XPost: comp.sys.cbm   
   From: mikeywyn@hotmail.com   
      
   "Darren Salt" wrote...   
   > True. But the *layout* of the display memory was certainly influenced by   
   > the   
   > CPU. The Spectrum's screen memory is laid out to take advantage of   
   > register   
   > pairing when writing character bitmaps (increment the high byte to get to   
   > the   
   > next line within a character cell),   
      
   I think you're wrong.   
      
   I believe the Spectrum display memory is arranged as it is to simplify the   
   hardware design and save silicon space inside the ULA.   This has nothing at   
   all to do with taking advantage of register pairs and such like (That is   
   probably just a side effect of the design).  Spectrum display memory is   
   arranged so that only one counter is needed to fetch both bitmap and   
   attribute with a simple 2-to-1 line decoder selecting which.   
      
   MikeW   
      
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