XGPSYN displays pages from .XGP files (as produced by PUB and POX), on the
video synthesizer. It can show half pages at high resolution, full pages
lying on their side at barely readable resolution, or two unreadable pages
side by side, with their large scale structure visible.

To use it say R XGPSYN and give it your file name when it asks. The .XGP
extension is assumed, and need not be typed. Then tell it the density you
want, H (1/2 page), F (1 page) or D (2 pages).  Next it goes into a loop
asking for page numbers. In H density you may specify a non integer page,
3.5, for example, to see bottom half of page 3. In F density specify the
full page you wish to see.  In D density the page you give, and the next
one, are displayed.  When the program types DONE, you may look at the
output at data disc terminals with <esc>47S. It usually helps to adjust
brightness and contrast.

Note that page 1 in .XGP files contains the font descriptions, and is not
interesting to display. Specifying page 0 (<cr> will do) or page 1 will
pop you out of the page loop and back to the density question.

The video synthesizer is a video rate D/A driven by data disc channels 30
through 37. H density requires 3 of these channels, F needs 4 and D wants
5. These are rarely available during heavy system load periods.  It uses
about 15 seconds of CPU time to compose a single page.

comments to HPM.