Call PCXDUMP screen-dump function with
|Notes:||If BX=0001h, 0003h, 0007h or 0008h the whole screen will be dumped; the
other valid values will draw a selection frame on the screen except in
text modes (text modes allow only full screen dumps).
This function doesn't perform the dump, it only requests it; the dump will be performed after a few milliseconds if it's safe to do so, thus the author recommends putting a 60 ms delay after this call.