The ImageWriter II and ImageWriter LQ interleaving problem (where two or
more different printing jobs are interleaved together) is a carry-over
from the days of the 128K/512K systems. Because of the limited memory of
those systems, it was necessary to spool the file being printed to one page
at a time. This meant a multi-page document would be sent as a series of
print jobs -- not as one complete job. Software manufacturers knew of this
limitation and wrote their applications accordingly.
Many of these manufacturers continue to use the same print routines, with
additions for new features, rather than rewrite them to more fully use the
features of the drivers.
Print drivers maintain connections with any networked printer for the
duration of the current print job. As long as applications still use the
older style of one-page-per-job, the interleave problem will continue.
Many newer manufacturers are now writing the applications as recommended
by Apple in "Inside Macintosh", so the problem is slowly diminishing.
AppleShare Print Server will resolve this problem. It contains a process
whereby the user can specify the time-out interval between pages of a print
job.
If the time-out is set to 1 minute (for example), any jobs sent by a user,
with less than a minute between them, will be printed as one job. However,
if a short interval (perhaps 10 seconds) is set, and it takes 15 seconds to
send the next page, another user's job could be queued in between the two
pages, and the interleave problem would still exist. There is no set value
for the time-out feature that will work with every application. The default
value is 5 seconds. Some applications may need a higher value if they
require more time to set up the print job.