Contents:
=========

    * Print density variation from RISC OS 2.
    * Updating !Printers
    * Turbodrivers


Print density variation from RISC OS 2.
---------------------------------------

You may find that printouts are lighter or darker
under RISC OS 3 than they were in RISC OS 2. This
is usually due to a change in the amount of
interlacing being performed ie. the number of
passes the print head makes over the same section
of the paper.

For example a Canon BJ-300 printer under RISC OS 2
with !PrinterDM set to "EPSON LQ-850 compatible
(360 by 360 dpi)" and the printer set to Epson LQ
emulation mode will make two passes over the paper
due to using vertical interlacing. The same
printer under RISC OS 3 with !Printers using the
Canon.BubbleJet file set to 360 by 360 DPI and the
printer set to IBM emulation mode will only make
one pass over the paper. So the printout will be
lighter, but on the other hand it will take less
time to print and the quality will be higher since
no interlacing is being used. Also the ink
cartridge will last longer. In this example
running the printer in Epson LQ emulation mode
with the Epson.LQ-860 file set to 180 by 360 DPI
will give results which are almost identical to
the RISC OS 2 configuration.

In the general case, if you use 360 by 360 DPI in
any printer definition file which gives true 360
DPI vertical resolution (non-interlaced), then
this will give lighter print than any of the 360
by 360 DPI standard Acorn !PrinterDM settings,
which are all interlaced. The files which use true
360 DPI vertical resolution are Canon.BJ-130e,
Canon.BJC-800 (usable with Star SJ-48) and
Canon.BJ-130e. Switch to a 180 by 360 DPI
resolution in a more standard file (eg.
Epson.LQ-860) if you need the interlacing to get
darker print.

Conversely take an Epson LQ-850 printer under RISC
OS 2 with !PrinterDM set to "EPSON LQ-850
compatible (360 by 360 dpi)". This again will make
two passes over the paper. The same printer under
RISC OS 3 with !Printers using the Epson.LQ-860
file set to 360 by 360 DPI will make four passes
over the paper since it is now horizontally
interlaced as well as vertically interlaced. (In
fact RISC OS 2 never really achieved 360 DPI
horizontal resolution since it didn't interlace it
and the printer will not print adjacent dots. The
only benefit this gave was 360 DPI positional
accuracy of left hand edges.) So the printout will
be darker and the resolution will be better, but
on the other hand it will take longer to print and
will wear the ribbon out faster. In this
particular example using 180 by 360 DPI in
!Printers will give results which are almost
identical to the RISC OS 2 configuration.

In the general case, if you use any resolution in
any printer definition file which is horizontally
interlaced, this will give darker print than the
same resolution under !PrinterDM. In practice this
is 240 DPI horizontal for 9 pin printers (240 by
72, 240 by 144 and 240 by 216) and 360 DPI
horizontal for 24 pin printers (360 by 180 and 360
by 360) although not all of these resolutions are
available as standard in !PrinterDM. If you need
to get the same print density as you did on RISC
OS 2, halve the horizontal resolution you are
using to 120 DPI or 180 DPI. If the extra
positional accuracy of left hand edges that RISC
OS 2 gave you turns out to be important, then edit
the horizontally interlaced graphics resolution
you are using (eg. 240 by 216) with !PrintEdit and
change the "X interlace:" field from 1 to 0 which
will disable the horizontal interlacing. (Note
that you cannot simply disable vertical
interlacing in a similar manner. Other changes
would be required.)


Updating !Printers
------------------

It will sometimes be necessary to update !Printers,
either to incorporate upgrades or to modify some
support information to drive a new printer. You
should refer in the first instance to any release
notes with the update.

Previous releases of !Printers have suggested adding
files within !Printers as required. This is now STRONGLY
discouraged. There should be no reason whatsoever for
any file within !Printers to be changed by anyone
except RISCOS Ltd.

Given that this is the case it should be possible to
upgrade !Printers just by renaming the old one away
(for safety) and then copying the new !Printers in.

If you feel you have to add a file into the search
path for !Printers then add it into the appropriate
directory within the "Choices:" structure (typically
!Boot.Choices.Printers).


Turbodrivers
------------

Some users persist in wanting to use Computer Concepts
Turbodriver software; despite the fact that it is now
unsupported some people feel that it still offers enough
extra functionality to be worth the hassles involved in
making it work.

Turbodrivers used to require small changes to be made to
the !Printers.!RunImage file on installation - this is
no longer necessary as we have incorporated these changes
into !Printers itself. As no new releases of Turbodrivers
are being made the installer does not understand recent
versions of !Printers. We therefore recommend that you
either:

 1) Install into an old version of !Printers and copy
    the required files into the Choices structure as
    possible.

 2) Manually copy the required files from inside the
    turbodriver installer to the Choices structure.
