XPost: comp.sys.sinclair, comp.sys.atari.8bit, comp.sys.apple2   
   XPost: comp.sys.cbm   
   From: bv@wjv.com   
      
   In article <4DDF9231A0%news@youmustbejoking.demon.cu.invalid>,   
   Darren Salt   wrote:   
   >I demand that Andrew Owen may or may not have written...   
   >   
   >> Bill H wrote:   
   >>> Relying on my memory and a cursory check on a number of websites it   
   >>> appears that the majority of Z80 cpu based computers had black and white   
   >>> displays, where as the majority of 65xx computers had a color display.   
   >   
   >> I must admit I can't think of a 6502 based machine that only had mono   
   >> graphics, [...]   
   >   
   >Acorn Atom, I think.   
   >   
   >>> Now there are exceptions to this, but it makes me wonder, did the CPU   
   >>> influence the display?   
      
   >> Usually the display was handled by a video processor.   
      
   >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), and Acorn's 8-bit machines (at least the BBC   
   >and Electron) used a layout such that each character cell used a   
   >contiguous chunk of memory (8, 16 or 32 bytes, depending on the   
   >number of colours).   
      
   On two of my first machines the video really didn't have a lot of   
   processing.  There was a character generator chip and you wrote a   
   character to a memory spot and it displayed on the screen.  Pure   
   memory mapped without a lot of overhead like we saw on machines   
   that came along in 1979 and 1980.   
      
   --   
   Bill Vermillion - bv @ wjv . com   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)