Artifact in text mode

[gardners]

In C64 mode the following code:

POKE53280,0:POKE53281,1:POKE646,0:POKE199,1:FOR T=1 TO 800:?" ";:NEXT T

shows a thin white line on the right side just before the border
starts but after the screen content ends. It looks as if the content
of the screen is displayed half a dot-cycle too early...

It seems that this also affect the C65-mode. If you run the following
basic code in C65-mode just after booting up the machine:

FORT=1TO1000:?"R ";:NEXTT (The R in the print string is CTRL-9
(Revers mode on))

you can see (beside other wired horizontal lines that are appearing on
screen) that the white screen content does not align with the yellow
border on the right side. You can see a small blue line of the
background color. In addition I think it overlaps half a dot-cycle on
the left side.