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Merge pull request #997 from zoltanvb/bbc_micro
Documentation for b2 core (Acorn BBC Micro emulation)
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‎docs/image/core/b2/bbc-micro-keyboard.png

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‎docs/image/core/b2/iso-mapping-for-bbc-micro.png

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‎docs/library/b2.md

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# Acorn - BBC Micro (b2-libretro)
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## Background
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Emulate the BBC Micro, a series of microcomputers designed and built by Acorn Computers Limited in the 1980s for the Computer Literacy Project of the BBC.
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The b2-libretro core has been authored by:
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- Tom Seddon (b2)
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- Zoltan Balogh (libretro core specific modifications)
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The b2 core is licensed under [GPL v3](https://github.com/zoltanvb/b2-libretro#licence). A summary of the licenses behind RetroArch and its cores can be found [here](../development/licenses.md).
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## Requirements
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No special requirements. To be tested yet on low end platforms.
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## Extensions
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Content that can be loaded by the b2 core have the following file extensions:
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- `.ssd/.dsd` - Floppy disk image
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RetroArch database(s) that are associated with the b2 core:
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- None yet
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## Features
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Frontend-level settings or features that the b2 core respects.
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| Feature | Supported |
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|-------------------|:---------:|
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| Restart | ✔ |
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| Saves | ✕ |
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| States | ✕ |
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| Rewind | ✕ |
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| Netplay | ✕ |
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| Core Options | ✔ |
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| RetroAchievements | ✕ |
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| RetroArch Cheats | ✕ |
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| Native Cheats | ✕ |
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| Controls | ✔ |
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| Remapping | - |
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| Multi-Mouse | ✕ |
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| Rumble | ✕ |
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| Sensors | ✕ |
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| Camera | ✕ |
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| Location | ✕ |
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| Subsystem | ✕ |
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| [Softpatching](../guides/softpatching.md) | ✕ |
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| Disk Control | ✔ |
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| Username | ✕ |
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| Language | ✕ |
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| Crop Overscan | ✕ |
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| LEDs | ✕ |
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## Directories
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No additional directories used, only content disk image is needed.
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## Geometry and timing
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- The b2 core's core provided FPS is 50
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- The b2 core's core provided sample rate is 250 kHz (to be optimized)
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- The b2 core's base width is 768
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- The b2 core's base height is 288
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- The b2 core's max width is 768
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- The b2 core's max height is 576 (interlace mode)
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- The b2 core's core provided aspect ratio is 4:3
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## Usage
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Load any supported content file. Content type will be autodetected, and if possible, started:
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- If disk image name contains an executable file name in brackets (such as `[CHUCKIE]`), a `CHAIN` command will be issued shortly after initial booting
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- If disk image name does not contain such indication, Shift key press will be simulated during boot to trigger autoboot function
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In case of multi-disk games, use the Disk Control menu to add the subsequent images and switch between them.
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## Core options
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The b2 core has the following option(s) that can be tweaked from the core options menu.
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- Emulated machine
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- `B/Acorn 1770`
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- `B/Watford 1770 (DDB2)`
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- `B/Watford 1770 (DDB3)`
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- `B/Opus 1770`
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- `B/Opus CHALLENGER 256K`
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- `B/Opus CHALLENGER 512K`
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- `B+`
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- `B+128`
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- Autoboot (on|off)
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- Keyboard assignments for each RetroPad button
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## Joypad mapping
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The analogue joysticks are mapped to the left analog stick and face button A for RetroArch player 1 and 2 slots.
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Joypad is fully assignable to keyboard keys in core options.
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## Keyboard
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Keyboard layout of the BBC Micro:
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![](../image/core/b2/bbc-micro-keyboard.png)
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Most mappings are straightforward positionally from an ISO UK keyboard:
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- Dark green: natural mapping, both position and function matches nicely
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- Light green: either position or function is slightly different
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- Yellow: function is different
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- Red: extra mapping
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- Dark grey: keys intentionally reserved for RetroArch / OS functions
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![](../image/core/b2/iso-mapping-for-bbc-micro.png)
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Exceptions are marked in the following table:
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| RetroKeyboard Inputs | BBC Micro keyboard input |
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|------------------------------|---------------------------|
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| Keyboard F10 | f0 |
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| Keyboard F11 | Break |
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| Keyboard Pause | Break |
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| Keyboard Backspace | Delete |
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| Keyboard Backquote ` | Escape (alternative mapping) |
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| Keyboard Equals = | ^ (caret) |
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| Keyboard Oem 102 | \\ (backslash) |
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| Keyboard Home | \\ (alternative mapping) |
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| Keyboard Backspace | Delete |
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| Keyboard Left Bracket [ | @ (at) |
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| Keyboard Right Bracket ] | [ (left bracket) |
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| Keyboard End | _ (underline) |
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| Keyboard Quote ' | : (colon) |
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| Keyboard Backslash \ | ] (right bracket) (shown as # in ISO map) |
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| Keyboard Delete | Delete |
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| Keyboard PgUp | Caps Lock |
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| Keyboard PgDn | Shift Lock |
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| Keyboard NumLock | Shift Lock |
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| Keyboard Insert | Copy |
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## External Links
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- [Official b2-libretro core repository](https://github.com/zoltanvb/b2-libretro)
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- [Libretro b2 Core info file](https://github.com/libretro/libretro-super/blob/master/dist/info/b2_libretro.info)
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- [Report Libretro b2 Core Issues Here](https://github.com/zoltanvb/b2-libretro/issues)
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- [Original b2 Implementation](https://github.com/tom-seddon/b2)
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- [Complete BBC Micro Games Archive](https://www.bbcmicro.co.uk/)
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- [Stardot forums](https://www.stardot.org.uk/forums/) - BBC Micro community

‎mkdocs.yml

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- '3DO Emulation':
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- 'The 3DO Company - 3DO (Opera)': 'library/opera.md'
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- '3DO Compatibility List': 'library/compatibility/3do.md'
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- 'Acorn Emulation':
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- 'Acorn - BBC Micro (b2)': 'library/b2.md'
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- 'Amstrad Emulation':
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- 'Amstrad - CPC (Caprice32)': 'library/caprice32.md'
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- 'Amstrad - CPC (CrocoDS)': 'library/crocods.md'

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