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© Copyright 1988 CBM (UK) Ltd. All rights reserved.
Commodore Business Machines (UK) Ltd.
Commodore House, The Switchback,
Gardner Road, Maidenhead,
Berks SL6 7XA
THE EMULATOR is a program which will give your Amiga the
appearance of a BBC Model B with BASIC 2 and DPS. THE
EMULATOR will run BBC BASIC with the most commonly used
VDU and *FX calls, and call 6502 subroutines.
It runs as a PROCESS on its own screen within the Amiga multi-
tasking operating system, which means you can run THE EMU-
LATOR at the same time as other Amiga programs such as
editors and Workbench accessories. Therefore, if you have an
Amiga 2000 with a Bridgeboard and 3 Mbytes of memory, you can
run BBC applications, PC applications, and native Amiga applica-
tions at the same time — with no data transfer problems between
the environments. You can even run several EMULATORS at
The principal objective in creating THE EMULATOR is to run
existing educational software, written in BBC BASIC or in a mix-
ture of BBC BASIC and 6502 assembler. This has been achieved
without any degradation of the Amiga's native advantages, such
as split screens and multi-tasking.
THE EMULATOR strategy has been to create a "bridge" from the
BBC operating system to the Amiga's operating environment. This
means THE EMULATOR can run nearly all "legal" BBC software
which uses BASIC and the OS. However, THE EMULATOR
cannot run "illegal" software that dodges the OS and goes directly
to the BBC screen memory or to the hardware. In practice, this
means THE EMULATOR can run nearly all educational programs
written in BASIC or a mixture of BASIC and assembler, but not
programs such as arcade-style games.
Principal components of THE EMULATOR software are as fol-
Beebos: A "bridge" from the BBC operating system through to the
Amiga graphics libraries, maths libraries, etc. Nearly all BBC calls
are supported, including OSBYTE (*FX calls).
DPS: "Disk Furtling System" — a bridge from DPS through to
BASIC: A new implementation of BBC BASIC, re-coded from
scratch in 68000 assembler. It is as compatible as possible with
6502: This emulation of the 6502 chip — written in 68000 assem-
bler — enables programs to call assembler subroutines.
Other elements in the software are a "CLI environment" entered
by *GO, and a simple 6502 monitor, entered by 'MONITOR.
This documentation assumes basic familiarity with the Amiga
environment as explained in the Amiga User Guide; it also
assumes familiarity with the BBC computer. Material which needs
a more advanced understanding of the Amiga are flagged as
"Tech notes" — ignore these if you want to.
To get started double-click on THE EMULATOR Icon. If you are
running on a single drive system you may be prompted to reinsert
your Workbench to allow THE EMULATOR to load certain Amiga
system liBraries. You will then be in THE EMULATOR.
Note that THE EMULATOR expects to find BASIC in the same
drawer as itself. If THE EMULATOR can't find BASIC a CLI
window will appear with a '*' prompt.
To PAUSE THE EMULATOR, perform a mouse-click anywhere in
THE EMULATOR screen. This will also present you with an
Amiga "drag bar" at the top of the screen which can be used to
pull the screen up and down, or rearrange it relative to the
Workbench and any other screens you may have open. With THE
EMULATOR in pause mode, it is possible to run various acces-
sories from the Amiga Workbench and Extras disk, including
Palette and GraphicDump utilities. To get rid of the drag bar and
run THE EMULATOR, click again anywhere in THE EMULATOR
screen below the drag bar.
To EXIT THE EMULATOR, enter the special command:
Tech Note: In order to run properly, THE EMULATOR needs to
have at least 300 kbytes free memory, and to be able to find
'mathstrans.library' in its LIBS: directory. If these conditions are
not met, it will fail to open. To gain maximum speed in 6502 emu-
lator, THE EMULATOR uses one or two elegant routines — this
means THE EMULATOR will run on a system with a 68010 or
68020 unless you disable instruction caching (68020), and run a
utility to catch MOVE SR instructions (68010 and 68020).
The keyboard
A good idea when first entering THE EMULATOR is to press
CAPS LOCK — this will allow you to talk to BASIC sensibly.
THE EMULATOR pays attention to your Keymap and Preferences
settings as determined by your Amiga Workbench. Your
Preferences determine such attributes as display positioning and
key repeat delays — these can be changed from within THE
EMULATOR by *FX 11 and 12 if necessary. The numeric keypad
works as you would expect.
Certain keys are "stolen" by THE EMULATOR to have special
effects. These are as follows:
Function keys — as BBC function keys; F10 used for FO
Cursor keys — as BBC cursor keys for copy key editing
Backspace — acts like BBC DELETE
Del — acts like copy key
Help —acts like BREAK
Note that some protection has been applied to the BREAK facility.
To BREAK it is necessary to hold down the left Amiga key (CBM
key on some ASOOs) then press the 'help 1 key. This performs a
"warm boot" like BBC BREAK; you can also perform a "cold boot"
by holding down the 'Ctrl' key and left Amiga then pressing the
help' key. Cold boot differs from warm boot in that it resets the
programmable function keys and resets the DFS — note that this
involves a few seconds pause for disk activity.
Graphics modes
THE EMULATOR supports the following graphics modes:
0 640x256 2 colours 80x32
1 320x256 4 colours 40x32
2 320x256 16 colours 20x32
3 text only 2 colours 80x25
4 320x256 2 colours 40x32
5 320x256 4 colours 20x32
6 text only 2 colours 40x25
7 Teletext display 40x25
In modes 2 and 5 the horizontal resolution is actually double the
original. The double width (20 column) characters are rendered
The BBC's Teletext (Mode 7) display is software emulated by THE
EMULATOR. Mode 7 is the fastest mode on the BBC, but the
slowest mode on THE EMULATOR. This is because the Amiga
has to emulate character-based hardware with pixel-based soft-
The speed of THE EMULATOR Mode 7 should be fast enough for
all practical application purposes; however, it is not recommended
for program editing. For this reason, the "power up default" for
THE EMULATOR has been set to Mode 6.
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