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Archive Magazine CD 1995
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volume_08
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issue_12
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1995-08-01
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Hints and Tips
8.12
‘Bad compression field’ − We have had a number of comments on the
subject of the Bad compression field error produced by Laser Direct and
the TurboDrivers, so many thanks to everyone who wrote in − too many to
mention you all.
8.12
The main causes seem to be either a lack of memory, or a lack of disc
space. The usual memory saving techniques apply, quitting unused
applications, reducing the screen resolution or number of colours and so
on. Lack of disc space is most frequent on floppy-only machines for
obvious reasons. During printing, a file is placed in the !Scrap
directory, so to ensure that you have as much space as possible, create
a scrap disc (preferably 1.6Mb if your computer will support it),
containing only the !Scrap application, and make sure that you double
click on that version before attempting to print. This will require
additional disc swapping, but should allow printing to continue
successfully.
8.12
NCS.
8.12
Booting problems − When exchanging the 80Mb hard drives in our two
A5000s for 430Mb drives, I reset the machine to auto boot, and had the
desktop auto boot option set, but do you think it would boot? The
solution was to issue a *OPT 4,2 command, from which point everything
behaved as anticipated. There were no discernible differences on
*STATUS.
8.12
This is a known bug in RISC OS 3. When you tick the auto boot option,
this should be set, but unfortunately it is not. The reason it makes no
difference to the status is that it is not a configuration option, but,
in fact, it writes the option to the disc. (If you do a *CAT then the
top line should read something like Dir. SCSI:: Words.$ Option 00
(Off); the option given will be the second number in the *OPT command.)
MH.
8.12
Alan Jackson, Oamaru, NZ.
8.12
‘Formatting’ hard discs − This has been covered several times in the
past but, unfortunately, we have had a number of people recently who
have experienced difficulty in preparing hard discs for use. While we
cannot provide a step-by-step description, since all the controller
cards are supplied with different software, many of the operations which
need to be completed are similar.
8.12
Remember that, for your particular system, you will need to read the
manual supplied with your hard disc controller card, or the HFORM
section of the manual if you are using a native drive (for example an
IDE drive on the Risc PC).
8.12
The most important point is that you MUST NOT actually format the drive.
If you do, you are more likely to damage the drive than make it usable!
All modern drives have the low level formatting laid down during the
manufacturing process, and trying to reformat the drive is likely to
damage the original formatting, but not completely replace it, rendering
the drive unusable.
8.12
Instead you need to initialise the drive. The precise wording will
depend on your controller card − Morley SCSI and HForm give you an
option to “Format or just Initialise the drive”, and the Cumana SCSI 2
card requires that you set up ‘partitions’ on the drive. The
initialisation process involves writing out RISC OS information about
the position of files on the drives, contents of the root directory and
so on, but does not do the potentially dangerous low level formatting.
8.12
NCS.
8.12
Quicksort − An error crept into Colin Singleton’s Programming Workshop
last month − at some point, the Basic program detokenised incorrectly.
All the ASC commands should be replaced with a minus sign to make the
program work. Thank you to all those who rang or wrote to point out the
error.
8.12
NCS.
8.12
Screenbanks − Following on from Matthew Hunter’s Programming Workshop
article on screen banking (Archive 8.8 p69), errors may not be displayed
because the error is written to the screen bank being updated, and not
the screen bank being viewed. By using the following procedure, you can
link both screens back together.
8.12
DEF PROCresetscreens
8.12
SYS 6,113,SB_bank%
8.12
SYS 6,112,SB_bank%
8.12
ENDPROC
8.12
The procedure could be called via the ON ERROR mechanism, or at the end
of the program.
8.12
Peter Prewett, Stirling, South Australia.
8.12
Snippet − Snippet is still a useful utility for screen grabs etc, but
refused to perform with my Risc PC. I queried 4Mation and obtained the
latest upgrade (in very short order and at no cost, which prompts me to
raise my hat to them), but still found the same problem of freezing the
machine when I tried to save a screen. The solution to this seems to be
to select a screen mode of no more than 256 colours, upon which, Snippet
behaves like the old friend it has always been.
8.12
Alan Jackson, Oamaru NZ.
8.12
Upgrading Video RAM − When upgrading the VRAM in your Risc PC from 1 to
2Mb, it is necessary to remove the 1Mb board and return it to be
upgraded. You should make sure that you reconfigure your computer to use
a screen resolution/number of colours which is possible even with no
VRAM, before removing the 1Mb board. If you do not do this, you will
find that you will need to reconfigure the computer ‘blind’, as the high
resolution modes are not available if there is no VRAM present, and no
picture will be displayed.
8.12
Fred Williams, Staffordshire.
8.12
Wimp bug (RISC OS 3.10) − If you are a Wimp programmer and have
experienced apparently inexplicable ‘Abort on data transfer’ and
‘Address exception’ errors ‘at’ addresses in the Window Manager module,
especially just after your program has quit, you may be interested (or,
like me, relieved!) to know that the problem may lie in a bug in the
Wimp.
8.12
According to a letter from Acorn, “there was a bug with ‘slabbed’ icons
(those with the R option in the validation flags). If you click on a
slabbed icon, and the program deletes the window it is on, or quits
before the wimp has a chance to redraw it, problems can arise.”
8.12
Hugh Eagle, Horsham.
8.12
Windows on the Risc PC − I would like to warn CD-ROM users that, due to
the fixed palette on the PC card, many CD programs will not work
properly − giving psychedelic colours which can lock up the computer. We
have found by pressing <f1> (in Windows) that the Windows help will be
opened, from which you can return to Windows. This prevents having to
reset the computer. Acorn/Aleph One are working on a fix for this
problem.
8.12
Peter Hughes, Desktop Laminations.