B-em is an emulator for various models of BBC Microcomputer as made by Acorn Computers in the 1980s along with a selection of 2nd processors. It is supported for Win32 and Linux/UNIX but may also work on other systems supported by the Allegro library.
B-em is licensed under the GPL, see COPYING for more details.
Development is active! If you want to know how to work with us, then please make sure you have a look at the SUBMITTING_PATCHES.md file
A TODO.md file exists, with ideas for future functionality for future versions of B-em.
B-em is maintained by a group of volunteers -- please enquire over on the stardot forums for more details.
You will need the following libraries:
Linux distros which include Allegro 5.2 at the time of writing include:
Allegro 5.2 packages for Ubuntu 16.04 LTS can be had from Launchpad
Open a terminal window, navigate to the B-em directory then enter:
./configure && make./autogen.sh && ./configure && makeYou will need version 5.2.2.0 of Allegro from:
https://github.com/liballeg/allegro5/releases/tag/5.2.2.0
Later versions have a bug which prevents the ticks in the menus from working correctly. There is a choice of compilers but these instructions only cover MingW and assume you have this correctly installed.
Unpack/clone B-Em into a folder and unpack the Allegro5 into a parallel folder, i.e. so the allegro folder and the b-em folder have the same parent and then from within the b-em folder run makebem.bat
| BBC key | PC key |
|---|---|
| BREAK | f12 |
| *: | @' |
| +; | :; |
| -= | -_ |
| ^~ | += |
| f0 | f0 (function keys are based on keycaps, not positioning) |
| 3# | 3 |
| 6& | 6 |
| 7' | 7 |
| 8( | 8 |
| 9) | 9 |
| 0 | 0 |
| Shift lock - | ALT |
The PC key Page Up acts as a speedup key and Page Down as pause.
The options are:
| Option | Meaning |
|---|---|
| Hard reset | resets the emulator, clearing all memory. |
| Load state | load a previously saved savestate. |
| Save state | save current emulation status. |
| Save Screenshot | save the current screen to a file |
| Exit | exit to OS. |
| Option | Meaning |
|---|---|
| Paste via Keyboard | send the contents of the clipbaord as keystoked |
| Printer to Clipboard | capture printer output and copy to clipboard |
| Option | Meaning |
|---|---|
| Autoboot disc 0/2 | load a disc image into drives 0 and 2, and boot it. |
| Load disc 0/2 | load a disc image into drives 0 and 2. |
| Load disc 1/3 | load a disc image into drives 1 and 3. |
| Eject disc 0/2 | removes disc image from drives 0 and 2. |
| Eject disc 1/3 | removes disc image from drives 1 and 3. |
| New disc 0/2 | creates a new DFS/ADFS disc and loads it into drives 0 and 2. |
| New disc 1/3 | creates a new DFS/ADFS disc and loads it into drives 1 and 3. |
| Write protect disc 0/2 | toggles write protection on drives 0 and 2. |
| Write protect disc 1/3 | toggles write protection on drives 1 and 3. |
| Default write protect | determines whether loaded discs are write protected by default |
| IDE Hard disc | Enables emulation of an IDE hard disc |
| SCSI Hard disc | Enables emulation of a SCSI hard disc |
| Enable VDFS | Enable a subset of host OS files to be visible as an Acorn filing system |
| Choose VDFS Root | Chose the directory on the host that is visible via VDFS |
| Option | Meaning |
|---|---|
| Load tape | load a tape image. |
| Eject tape | removes a tape image. |
| Rewind tape | rewind the emulated tape. |
| Show tape catalogue | shows the catalogue of the current tape image. |
| Tape speed | select between normal and fast tape speed. |
This menu shows the contents of the Sideways ROM/RAM banks and enables these to be loaded with a different ROM, enabled as RAM or cleared.
This lists the models in alphabetical order and enabled the model being emulated to be changed. Be aware this causes a reset.
This lists the available second processors and enabled one to be chosen. The choice in this menu is overridden if the model picked in the model menu is always supplied with a 2nd processor, for example the Master
| Option | Meaning |
|---|---|
| Line Doubling | stretch the BBC screen by doubling every line. |
| Scanlines | stretch the BBC screen by blanking every other line |
| Interlaced | emulate an interlaced display (useful for a handful of demos). Allows high resolution mode 7. |
| PAL | use PAL filter! |
| PAL interlaced | use PAL filter, with interlacing. Slow! Allows high resolution mode 7. |
| Option | Meaning |
|---|---|
| None | Remove all the black space around the image area. |
| Medium | borders intended to be attractive rather than accurate |
| Full | The full borders as seen on an old TV |
| Option | Meaning |
|---|---|
| Fullscreen | enters fullscreen mode. Use ALT-ENTER to return to windowed mode. |
| Option | Meaning |
|---|---|
| Internal sound chip | enable output of the normal BBC sound chip. |
| BeebSID | enable output of the SID emulation. |
| Music 5000 | enable output from an emulated Music 5000 synth |
| Printer Port DAC | enable output of 8-bit DAC connected to the printer port. |
| Disc drive noise | enable output of the disc drive sounds. |
| Tape noise | enable output of the cassette emulation. |
| Internal sound filter | enable bandpass filtering of sound. Reproduces the poor quality of the internal speaker. |
| Internal waveform | choose between several waveforms for the normal BBC sound chip. Square wave is the original. |
| Option | Meaning |
|---|---|
| Model | choose between many different models of SID. Many tunes sound quite different depending on the model chosen. |
| Simple method | Choose between interpolation and resampling. Resampling is in theory higher quality, but I can't tell the difference. |
| Disc drive type | choose between sound from 5.25" drive or 3.5" drive. |
| Disc drive volume | set the relative volume of the disc drive noise. |
| Option | Meaning |
|---|---|
| Redefine keys | redefine keyboard setup. Map CAPS/CTRL to A/S - remaps those 2 keys. Useful for games where CAPS/CTRL are left/right. |
| Option | Meaning |
|---|---|
| AMX mouse | enables AMX mouse emulation. |
Choose an soeed relative to a real model of that type.
| Option | Meaning |
|---|---|
| Debugger | Enters debugger for debugging the main 6502. Type '?' to get list of commands. |
| Debug Tube | Enters debugger for debugging the current 2nd processor. |
| Break | break into debugger. |
b-em [discimage|tapeimage|snapshot] [-u name.uef] [-mx] [-tx] [-i] [-c] [-fx] [-spx]discimage name.ssd/dsd/adf/adl/img etc.
tapeimage name.uef/csw
snapshote name.snp (previously saved snapshot)
-u name.uef - load UEF image name.uef
-mx - model to emulate, where x is
0 - BBC A with OS 0.1
1 - BBC B with OS 0.1
2 - BBC A
3 - BBC B with 8271 FDC
4 - BBC B with 8271 FDC + loads of sideways RAM
5 - BBC B with 1770 FDC + loads of sideways RAM
6 - BBC B US with 8271 FDC
7 - BBC B German with 8271 FDC
8 - B+ 64K
9 - B+ 128K
10 - Master 128 w/ MOS 3.20
11 - Master 512
12 - Master Turbo
13 - Master Compact
14 - ARM Evaluation System
15 - Master 128 w/ MOS 3.50
16 - BBC B with no FDC + loads of sideways RAM
17 - BBC B w/Solidisk 1770 FDC
18 - BBC B w/Opus 1770 FDC
19 - BBC B w/Watford 1770 FDC
20 - BBC B w/65C02, Acorn 1770
21 - BBC B with 65C02, no FDC
-tx - enable tube, where x is:
0 - 6502 (internal)
1 - ARM (Master only)
2 - Z80
3 - 80186 (Master only)
4 - 65816 (if ROMs available)
5 - 32016
6 - 6502 (external)-i - enable interlace mode (only useful on a couple of demos)
-c - enables scanlines
-fx - set frameskip to x (1-9, 1=no skip)
-fasttape - speeds up tape access
-spx - emulation speed where x is 0 to 9 (default = 4)
To initialise a hard disc, use the included HDINIT program. Press 'I' to investigate the drive - this will set up the default parameters for a 50 mb drive. If you want a different size press 'Z' and enter the desired size - it does not matter that this does not match the size given in the emulated hardware.
Then press 'F' to format, and follow the prompts.
Master 512 includes mouse emulation. This is used by trapping the mouse in the emulator window - click in the window to capture it, and press CTRL + END to release.
All disc images used by the Master 512 should have the .img extension - the type is determined by size. Both 640k and 800k discs are supported, as well as DOS standard 360k and 720k.
You can use the IDE hard disc emulation with this, run HDISK.CMD in DOS-Plus, then HDINSTAL.BAT. Go make a cup of tea while doing this, it takes forever! HDISK.CMD will create a file 'DRIVE_C' in ADFS so you will need to format the hard disc using ADFS first.
The ROMs for this coprocessor are not included with the emulator. You will need to acquire the file ReCo6502ROM_816 and place it in roms\tube.
The 65816 runs at 16mhz, regardless of what the firmware is set to.
| Processor | Meaning |
|---|---|
| The 6502 processor | All instructions should be emulated. Attempts to be cycle perfect. 65C02 is emulated for Master 128 mode. |
| The 65C12 tube | As a parasite processor. |
| The 65816 tube | As a parasite processor. Emulator from Snem. |
| The Z80 tube | As a parasite processor. Probably a few bugs. Emulator from ZX82. |
| The ARM processor | As a parasite processor for Master 128 only. Emulator from Arculator. |
| The 80186 tube | As a parasite processor for Master 512 only. Emulator from PCem. |
| The 6845 CRTC | Cycle-exact emulation. Runs everything I've tried, with all effects working. |
| The Video ULA | Cycle-exact emulation, though I think palette changes are a cycle off? Might be a delay in the real chip. |
| The System VIA | Keyboard and sound emulated. Also CMOS on Master-based models. |
| The User VIA | Emulated. |
| 8271 FDC | Double disc, double sided, 40/80 tracks, read/write. With authentic noise. Supports read-only access of protected FDI images. |
| 1770 FDC | Double disc, double sided, 40/80 tracks, read/write. With authentic noise. Supports read-only access of protected FDI images. |
| IDE hard disc | Emulates 2 discs. Emulation from Arculator. |
| SCSI hard disc | Emulates 4 discs. Emulation from BeebEm. |
| Sound | All channels emulated, with sample support and some undocumented behaviour (Crazee Rider). With optional bandpass filter. |
| BeebSID | Emulated using resid-fp, so should be pretty accurate. Is only emulated when accessed, to reduce CPU load. |
| ADC | Real joystick emulation, supporting both joysticks. |
| 6850 ACIA | Emulated for cassettes. Read only. |
| Serial ULA | Emulated. |
| Music 5000 | Hybrid synth emulated. Emulation from Beech |
| Music 4000 | Hybrid music keyboard. Emulated via MIDI, Emulation original to B-Em |
| Music 2000 | Hybrid MIDI I/F. Connects to host MIDI, Emulation original to B-Em |
Acorn for making the BBC in the first place:
David Allen,Bob Austin,Ram Banerjee,Paul Bond,Allen Boothroyd,Cambridge, Cleartone,John Coll,John Cox,Andy Cripps,Chris Curry,6502 designers, Jeremy Dion,Tim Dobson,Joe Dunn,Paul Farrell,Ferranti,Steve Furber,Jon Gibbons, Andrew Gordon,Lawrence Hardwick,Dylan Harris,Hermann Hauser,Hitachi, Andy Hopper,ICL,Martin Jackson,Brian Jones,Chris Jordan,David King, David Kitson,Paul Kriwaczek,Computer Laboratory,Peter Miller,Arthur Norman, Glyn Phillips,Mike Prees,John Radcliffe,Wilberforce Road,Peter Robinson, Richard Russell,Kim Spence-Jones,Graham Tebby,Jon Thackray,Chris Turner, Adrian Warner,Roger Wilson and Alan Wright for contributing to the development of the BBC Computer (among others too numerous to mention)