The performance of the LaserWriter for many applications has been
significantly improved in the new implementation of the LaserWriter
software. The main areas of improvement are as follows:
-- PostScript interpreter
The PostScript interpreter is substantially (30 to 40 percent) faster than
before. This improvement applies primarily to programs that are being
interpreted from procedures already stored in VM; programs being interpreted
from a file or string receive little benefit.
-- AppleTalk
Efficiency of AppleTalk communication has been improved by a buffer strategy
that permits greater overlap between the work being performed on the
LaserWriter and on the host. This is especially noticed when using Apple's
Print Manager on the Macintosh, which sends relatively short (512 byte)
blocks.
-- Throughput
Page throughput for many applications is significantly increased by a new
printing strategy that permits imaging of a page to be overlapped with
execution of the PostScript description for the next page. Formerly, page
imaging and PostScript execution were performed serially; the imaging time (up
to 6 seconds per page) was entirely wasted.
-- Compressed character mechanism
Page descriptions that print large characters may benefit from the compressed
character mechanism. Large characters now are often obtained from the font
cache, whereas formerly they were always produced by re-executing the
character descriptions.
-- Font cashe
Characters may be retained in the font cache even after removal of the font
definition from which they were generated. If the same font is later defined
again, the cached characters will be found and used if they still exist. This
depends on correct use of the UniqueID entry in the font definitions; see the
discussion under 'Modifying and creating fonts' in the PostScript Language
Tutorial and Cookbook.
-- Virtual memory
The total amount of virtual memory available is not exactly the same as in the
original LaserWriter, although it is close to being the same. This may affect
the maximum number of down-loaded and user defined fonts that can be present
simultaneously. Note that PostScript page descriptions with large preambles
can obtain significant VM space savings by making use of the packed array
facility.