laser-lovers@ucbvax.UUCP (01/19/86)
Well, we just got (finally!) our upgrade kit to turn one of our LaserJets
into a LaserJet Plus. We haven't given it a very thorough workout yet,
but it looks promising.
As expected, the change is basically a board swap. There are a ridiculous
number of screws that have to be undone to reach the board, but there is
nothing hard about it. Be warned that the instructions cannot be taken
too literally, because there seems to have been at least one revision of
the LaserJet's detailed mechanical design. If you have a relatively old
LaserJet (old == 1 year, say), you'll find that the "control panel shield"
alluded to in the instructions is simply missing, and that various other
details like the number of screws holding things down don't match the
instructions. A bit of cautious common sense suffices.
As predicted, the changes to the board are minimal. Much of it appears
identical, including the clock rate of the CPU. Also as predicted, the
two places where there *are* changes are the substitution of 256Kb RAMs
for 64Kb ones, and a change in the firmware ROMs. The old firmware was
a pair of cryptically-numbered ROMs, with a couple of conspicuous holes
nearby for two more; the new firmware is four 27256s.
The major changes are much more usable memory (395KB vs. 59KB) for graphics
and such, the ability to download fonts, and an optional Centronics parallel
interface for faster data transmission. (We don't have the parallel option.)
There are a number of useful minor touches: the ability to download a form
and have it overlaid on further pages automatically, an extra built-in font
(16.66-pitch portrait line printer), and a limited rectangle-filling feature
(including horizontal and vertical rule-drawing). Finally, they have fixed
a couple of human-interface botches: the printer goes on-line automatically
when its paper tray is refilled after running out, and there is a switch
setting (mentioned only in an obscure appendix) that tells the printer to
continue after a user-caused error, rather than hanging until somebody hits
the CONTINUE button.
There are some things that aren't fixed, though. The old "21" error, from
having too many patches of graphics side-by-side, still occurs. (This means
there is a strong incentive to download fonts rather than using graphics to
draw the characters, even if they are being used only once.) The printer
still uses its line to the host only to send XON/XOFF: it won't tell the
host how many pages it's printed (figuring this out in software, for
accounting, can be a real headache), it won't tell the host if it's stopped
because of some problem like running out of paper, and it won't tell the
host what font cartridge is present or what downloaded fonts are on hand.
One can make a downloaded font "permanent", which means that it doesn't
get cleared out by a "reset" sequence, but the utility of this is greatly
reduced because a powerdown still clears all downloaded fonts, and the
host can't tell whether this has happened! Finally, there still isn't
enough memory to download a full page of graphics at full resolution,
although you can do about half a page.
All in all, it's a significant improvement on the original LaserJet --
you should definitely buy a LaserJet Plus rather than a plain LaserJet,
unless you are desperately short of money -- but it's not as good as it
could be. Either LaserJet is dynamite as a daisywheel replacement. The
LJ+ looks like a decent typesetting engine, where the LJ was a severely
limited one. Neither is a real graphics machine. More memory and a way
to determine printer status would be welcome improvements.
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henry