Unmentioned Mixed Graphics -- Bob Bishop

["Bryan Parkoff" <nospam@nospam.com>]

Hello,

    We have discussed Bob Bishop earlier.  I know that it switches 
$C050/$C051 back and forth during 17030 video cycles so text and graphics 
can be mixed in half screen at the same time.  I want to mention that I am 
able to mix 40 column / 80 column at the same time using $C00C/$C00D.
    You can see 40 column in the upper half page and 80 column in the lower 
half page during 17030 video cycles.
    I do know that 40 column and 80 column have different horizontal 
alignment between horizontal blanking.  During Phase 0, it displays even 
text and during Phase 1, it displays odd text for 80 column.  During Phase 
0, it displays seven blanking pixels first before it displays half text 
during Phase 1 and other half text during Phase 0.  Then final half 40th 
character text is displayed during Phase 0.
    Look at two alignments below.

#######.................................................#######+++++++  80 
column -- First Phase 0 until Last Phase 1
+++++++##############.....................############## 40 column -- First 
Phase 1 until Last Phase 0

    Notice #'s is the 7 pixel that it runs at 14 MHz for 80 column. +'s is 
the blanking pixel (no pixel present) in the right.  Notice +'s is in the 
left for 40 column.  It ignores even character text for 80 column while it 
waits until Phase 1 before it displays character text for 40 column at 7 MHz 
as 14 pixels.

    My question is -- How did NTSC / RGB monitor align either 40 / 80 column 
horizontal between blanking perfect?  It looks like that delay may not be 
needed, but monitor adjusts horizontal line itself.

Bryan Parkoff