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Rev Author Line No. Line
4 lvd 1 
video resolution:
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lowres - 7MHz pixelclock (256 or 320 pixels per line)
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hires  - 14MHz pixelclock (512 or 640 pixels per line)
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videomode:
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attr   - two bytes per 8 pixels, bits and attribute
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text   - 2 bytes per 8 pixels, same as attr, but bytes are letter code and letter attribute
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16c    - 4 bits per pixel, 16 colors
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2c     - one bit per pixel, monochrome
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256c   - 8 bits per pixel
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16+16c - two 16c playfields with transparency
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table structure:
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MEMORY SPEED
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	VIDEO MODE
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		CPU SPEED/WAITS
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BW - available memory bandwidth usage: when 1, cpu stalls, when 1/2 or less - CPU runs nowait at Fcpu<=Fmemory.
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     When Fcpu>Fmemory and BW<1, there are wait states.
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-----------------------------------------------------------------------------------------
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3.5MHz, 8 bit memory:
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	lowres attr/text,
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	hires 2c:         BW=1/2
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		3.5MHz nowait
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		7MHz wait
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	lowres 16c,
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	hires attr/text:  BW=1
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		stall
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3.5MHz, 16 bit memory:
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	lowres attr/text: BW=1/4 (or 1/2 in lame schemes like ATM turbo or Profi)
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		3.5MHz nowait
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		7MHz wait
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	lowres 16c,
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	hires attr/text:  BW=1/2
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		3.5MHz nowait
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		7MHz wait
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	lowres 256c,
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	lowres 16+16c,
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	hires 16c:        BW=1
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		stall
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7MHz, 16 bit memory:
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	lowres attr/text,
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	hires 2c:         BW=1/8
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		3.5MHz nowait
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		7MHz nowait
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		14MHz wait
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	lowres 16c,
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	hires attr/text:  BW=1/4
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		3.5MHz nowait
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		7MHz nowait
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		14MHz wait
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	lowres 256c,
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	lowres 16+16c,
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	hires 16c:        BW=1/2
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		3.5MHz nowait
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		7MHz nowait
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		14MHz wait
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	hires 256c,
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	hires 16+16c:     BW=1
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		stall
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