Two or more AppleTalk ImageWriter users printing at the same time may find
that the ImageWriter "interleaves" the pages, switching between jobs. In
other words, the ImageWriter prints page 1 from the first document, then
page 1 from the second document, followed by page 2 from the first document,
page 2 from the second document, and so on.
The problem is caused because the application in use works by the
"spool-a-page / print-a-page" method of printing: the application prints
each page of a document as a separate job instead of calling PrPicFile to
print the entire picture file. Many applications adopted this method of
printing to avoid running out of disk space while the ImageWriter driver
was spooling the document to disk. Because printing code is moved from
application to application, this method is still in use.
Applications that use the method of printing described in "Inside Macintosh"
(ISBN 0-2-1-17737-4), Volume II, page 155, will print by job, and will not
interleaf. This method allows the multiple bin option of the ImageWriter LQ
to work correctly.
Short of asking the designers, the only method of testing which method a
given application uses is by testing it on multiple printing jobs.