Epson Apex 20020 - Manual (Page 182)

If the patterns on your screen are clear and distinct, press Y and
then
Enter.
If any pattern is not displayed clearly, check the adjustment of
your monitor and make sure it is connected properly. If a
problem still exists, press
N
and
Enter
to display the error
message.
Screen Paging Check
To check the screen paging of your monitor, press
7
and
Enter.
The video RAM on the color graphics adapter is divided into
eight independent display pages. This test checks the eight
pages by first filling all eight with a number corresponding to
the page and then displaying each page in turn. You see this
pattern for screen 0:
When you have examined this screen, press any key to display
the next page. The eight display pages, numbered 0 to 7, are
displayed sequentially.
After the eighth page is displayed, you see the prompt:
Is the display correct (Y/N)?