To: 999 (all members)
From: E5F (Dick Greening)
Subject: BEEB Emulators on RISC-OS
Martin Hodgson's (D7X) plea for other
Archie machine owners, running a BEEB
emulator, did not fall on deaf ears.
The reason I am late in commenting is
that I have been on another planet for
two months, (well BW Canals actually!)
I also would be interested in buying
8BS CD Roms, but my experience in
trying to unravel disc images
downloaded from the Internet, has made
me think again.
(This used a friend's AppleMac writing
to a DOS disc read by an Acorn 3010!
It also included transfering the files
via the RS423 from the Archie to the
BEEB!....VERY time consuming. And then
trying to reconstitute the double
sided disc by adding together two half
sized files per side with DiscDoctor!)
There has to be an easier way!!
Is there any bright spark out there
who can write a piece of software to
do the conversion? .........PLEASE!
ANYWAY this may all be academic in
the light of ACORN's present financial
situation, (we may all be forced to
use Windozzzeee........ God forbid!!
I was GIVEN a 386 ...I've tried to
like it.....HONEST.....It has only
been switched on once this year, and
that was to check the contents of it's
hard drive!!!)
Comments, as invited by our EDITOR....
YES there are people out there using a
BEEB emulator on a RISC-OS machine.
There are also people out there using
a RISC-OS machine to port 8-bit SW
from other sources to 5¼" discs and a
BBC model B!
Long live or is it to late??
To: 999 (all members)
From: D7X (Martin Hodgson)
Subject: 8BS CD-ROM 1 continued.
I was very interested to read John
Crane's comments on 8BS 66.
Firstly, running FDC on a PC (or
card). It is typically DOS unfriendly.
You run the programme and it just sits
there - daring you to do something.
Actually, you just type in the
instructions as given by Chris, press
RETURN, the discs start spinning and
it does its job quite effectively.
I have been persevering with trying to
get the CD to work on my A5000, using
ImageDFS.
If you open the !ImageDFS directory
(hold SHIFT and double click the mouse
on it), you can load !Boot and !Run
into Edit. The line :-
Set Alias$@RunType`BBC Run
<ImageDFS$Dir>.!Run %%*0
is what loads and runs ImageDFS when
you click on a BBC image file. The
`BBC needs to be changed to `FFD
Likewise in the line :-
Set File$Type`BBC DFSImage
Note that ` is the underscore
character.
There is a similar line in !Run.
Having done this, when you double
click on one of Chris's image files,
it loads and runs ImageDFS. The file
type &FFD is the data file type, which
RISC-OS assignes to any unknown file,
e.g. those on the CD.
However, ImagDFS then crashes out with
the "general read file error".
So, the file !RunImage, which is in
BASIC, but crunched, contains five
references to &BBC. I used a disc
editor to change these to &FFD, to no
avail. The CD files will load in OK if
I copy to hard disc and filetype them
&BBC. Consequently the problem must be
in the module file ImageDFS (not
!ImageDFS please note), or perhaps in
the file LoadIDFS. These are not in
BASIC, but appear to be compiled.
Editing those files looks like being
impossible. The only hope is to
persuade Warm Silence Software to let
somebody have the source code to amend
it.
On the matter of double-sided disc
images, ImageDFS can create and read
these itself. It will not read Chris's
interleaved images, but presumably
requires the sides concatonated
together - as Chris has done for the
ADFS disc images.
To: 999 (all members)
From: D7X (Martin Hodgson)
Subject: Disc Images PC / ACORN
8BS CD-ROM 1 IMAGE FILES on RISC-OS
computers.
Whilst the lack of Filetyping of the
disc images on the CD can be overcome
(copy the image to your hard disc and
FilteType it &BBC) there seems to be
no way you can read any of the
Double-sided images.
!ImageDFS is able to read the
single-sided images, one side at a
time, but will not read the
interleaved double sided images.
Chris has also provided the ADFS
images in which the two sides are in
the image file one after the other,
non-interleaved, but ImageDFS will not
read ADFS anyway. I have resorted to
my PC and FDC.EXE to try and make
similar DFS files, but find FDC.EXE
will only produce interleaved disc
images.
On the Acorn machine, ImageDFS does
produce double sided disc images, in
which the two sides are
non-interleaved. These are then
useable by !BBCEm, but not by PcBBC on
the PC because that will only read
interleaved images. With
non-interleaved images PcBBC reads the
first side, but is not aware of the
second side.
CHris , in putting together the 8BS CD
ROMs has in fact covered all the image
fomats one might need, except for
these DFS non-interleaved images.
There is room on the CD for this,
final (I think) format to be added. I
will happily reconstitute the 63 discs
from CD ROM 1 on my PC, then use
!ImageDFs on the Acorn to make
non-interleaved images. Perhaps Chris
would then be kind enough to add them
to the CD at some point in the future.
To: 999 (all members)
From: CNC (Carlo Concari)
Subject: Hello everybody!
Hello there,
I'm Carlo Concari from Italy, proud
owner of an Olivetti Prodest PC 128S,
aka a relabeled BBC Master Compact.
I had it since I was 11, and learned a
big deal about computers on that neat
little machine.
Unfortunately I never had access to
telecom networks or BBSs back in the
days. Living in a rural part of Italy
we didn't even have a home telephone
until 1989, go figure!
All my programming was done solo, so I
love to have a chance to distribute
some of my efforts. Thanks Chris!
I have a few contributions for this
issue (bear with me please), but the
piece of software I'm most proud
of is a version of Tetris I wrote in
1991/1992. The game is utterly
incomplete (no sound, no scoring, no
levels) but playable. Have a good
laugh with my English (I was just
studying it in middle school at the
time) and the graphics (I really can't
draw). Also pass over the eyesore
colour scheme if you can: the game was
entirely developed on a green phosphor
monitor on which it all seemed rather
greenely pleasant anyway.
All the best,
- Carlo.
To: 999 (all members)
From: CNC (Carlo Concari)
Subject: SS ADFS copy protection
Last year, fearing that 25 years old
floppy discs could soon start failing,
I've been making disc images of all my
BBC floppies.
The only ones I haven't been able to
copy are the original Superior
Software games, that employ a rather
sophisticated copy protection scheme.
I remember that a friend who owned an
Amiga was the only one who was able to
create fully working copies of those
discs; don't know what copier software
he used though.
Finding no info on the Internet I dug
out the disassemblers and debuggers I
wrote circa 20 years ago and set out
to investigate the copy protection
scheme.
To make a long story short, it turns
out that Superior discs are split into
three parts:
* Several regular ADFS MFM tracks that
contain boot files and loaders;
* One special track which is checked
by the copy protection scheme;
* Many FM tracks carrying the games
themselves; these tracks are read by
the loaders once the special track
is validated.
The special track is a really tricky
beast! The core of the protection
scheme is that it is readable both in
FM and MFM modes, and in each mode it
sports four 512-byte sectors with
logical IDs $F0 to $F3.
Now, if you do the math, you will find
that 4*512 bytes in MFM mode plus
4*512 bytes in FM mode take up more
than a full track!
Using the mighty Advanced Disc
Investigator ROM I found out that the
odd numbered sectors start halfway
through the preceding even ones, thus
saving considerable space.
Incidentally, this wreaks havoc with
the odd sectors which assume a bad
CRC, which is required #to be bad# by
the loaders anyway!
A simple patch to the loaders enabled
me to copy the discs, but what I'd
like to do for pure research spirit is
write a piece of software to create
such a track by direct access of the
WD1770 FDC.
I'm thinking about writing the four
MFM sectors, then suddenly switching
the controller to FM mode and writing
the four FM sectors while the disc is
spinning. Stay tuned, who knows, I
could even find the time to really try
this out! :)
To: 999 (all members)
From: CNC (Carlo Concari)
Subject: Model B games on the Compact
I've been downloading tons of BBC games
from the Internet lately, which are
filling me with uncountable nostalgia.
How I'd have loved to have access to
all this stuff back in the good old
days... Now that I have it I haven't
got time to play. Ain't life unfair?
Anyway, most of the 8 bit games for
Acorn machines are coded for the BBC
Micro, and I had some fun lately doing
some reverse engineering and adapting
them to my Master Compact clone.
Most problems arise from random *DISC
commands scattered around game loaders.
The Compact has no tape interface, so
MOS 5.10 disposed of *DISC which it
considers a Bad command. Get rid of all
the *DISC instances (some even found as
OSCLI calls in machine code portions,
as in Repton games) and chances are the
game will run on the Master Compact.
A couple of games had to be tweaked
deeper though.
Citadel kept freezing at the 'Welcome
to...' message. It turned out that the
game checks the type of machine it is
running on using OSBYTE &00. This call
returns 1 for the BBC, 3 for the
Master 128, 5 for the Compact. The
game was only checking for a Master
128, while the Compact was treated as
a regular B causing the game to freeze.
This is the relevant machine code from
the file CITAL:
5720 LDX £&01
5722 LDA £&00
5724 JSR &FFF4
5727 TXA
5728 CMP £&03
572A BEQ &572D
572C RTS
572D JSR &5690 ;patch for Master
The fix, as suggested by Richard
Talbot-Watkins, is to change the BEQ
at 572A into a BCS.
Airwolf had to be tweaked as well. The
game itself was working ok, but it had
issues in the attract screens fonts,
which it redefines. Master series
machines, in fact, manage fonts quite
differently from the BBC Micro. To
solve the problem I wrote a patcher
that needs to be applied once. It
modifies the file Wolf1 to work on
both classes of machines. The patcher
is included in this issue.