XRoar features

High- and low-level features of XRoar, a Dragon and Tandy 8-bit computer emulator. Some features listed may only currently be available in the latest snapshot build or a development branch of the git repo.

• https://www.6809.org.uk/xroar/ - XRoar homepage
• https://launchpad.net/~sixxie/+archive/ppa - snapshot builds for Ubuntu
• https://www.6809.org.uk/tmp/xroar/ - snapshot builds for Windows and (sometimes) Mac OS X

GUI

• Most featureful user-interface is using GTK+ (2 or 3) on Unix, closely followed by Windows. GTK+ 3 is preferred; I will support GTK+ 2 for as long as it and GtkGLExt exist in Debian, but this may not be for very long now.
• Mac OS X interface provides some menus.
• Fallback SDL2 interface presents no menus and uses keyboard shortcuts only.

Systems

• Dragon 32 & 64, Tano Dragon.
• Eurohard Dragon 200-E.
• Tandy Colour Computer 1, 2, & 3.
• Tandy MC-10, Matra & Hachette Alice 4K.
• Dragon Professional (Alpha, unreleased).
• Tandy Deluxe Colour Computer (unreleased).

Video

• Accelerated video using GLArea, SDL2 or GtkGLExt. Note that GtkGLExt may well not be in the next release of Debian.
• PAL or NTSC machines emulated (Dragon, CoCo, MC-10).
• Composite video simulation, multiple combinations of pixel and chroma frequency.
• Frame skip supported for slow machines.

Audio

• Wide variety of sound drivers supported including OSS, ALSA, PulseAudio, CoreAudio and SDL2.
• Mux selection between DAC output, tape input and cartridge generated sound.
• Output level interactions of mux selection and single-bit output measured and implemented.
• Feedback into single-bit pin configured as an input supported.
• SN76489 support, used in the Games Master Cartridge.
• AY-3-891x support, used in the Dragon Professional and Tandy Deluxe Colour Computer.

Keyboard

• Host keyboard positions closely mapped to emulated keyboard positions.
• Host keyboard layout can be specified to get this mapping right.
• Translated mode available - host key value mapped to emulated key value.
• Keyboard matrix ghosting.
• Most emulator functionality available through Ctrl+key or Ctrl+Shift+key.

Joysticks

• Physical joysticks supported through SDL2, libevdev or the Linux joydev API.
• Virtual joystick defaults to keyboard-based, using cursors + Left Alt.
• Mouse-based virtual joystick available. Maps screen position to joystick position.
• Arbitrary configuration of each of a joystick's axes and buttons from any input source allowed.

Tapes

• CAS/C10 file input and output with optional CUE data supported.
• Read-only K7 support, a format used to distribute some Alice software.
• WAV file input and output supported.
• More general audio file input and output supported with libsndfile.
• Tape used for reading is separate from tape used for writing. Imagine two tape decks being connected, one to the input lead, one to the output. The motor control applies to both.
• Play/pause control. Required for MC-10 as it has no motor remote.
• Accelerated tape loading by intercepting ROM calls.
• Special mode intercepts ROM calls and rewrites any data read from the input tape to the output tape.

Disks

• Reads and writes DSK (JVC), VDK and DMK format disk images.
• Supports setting write-protect on disks.
• Supports toggling write-back for disks. Disk data is held in memory and only written out on disk change or emulator shutdown, and then only if write-back is enabled (which it is by default, so be careful).
• Disk is automatically expanded when a new track is written.
• DragonDOS, Delta and RS-DOS cartridges supported.
• WD2791, WD2793, WD2795 and WD2797 floppy controllers supported.
• "Becker port" supported for communication with pyDriveWire or Drivewire 4.
• OS-9 filesystems on headerless DSK (JVC) format images can provide geometry hints (sides, heads).

Other cartridges

• Orchestra-90 stereo sound cart supported.
• ROM carts with or without FIRQ-based autostart supported.
• Code supports arbitrary interface, providing address, data and P2 select information.
• Games Master Cartridge support, including the SN76489 sound chip.
• NX32 and MOOH support, accessing SD card image.
• Glenside IDE support, accessing HD image(s).
• MCX128 cartridge supported for MC-10.

ROMs

• ROM images are simple binary dumps.
• DGN format also supported, but header is ignored.
• Machines are configured with BASIC ($A000-) and/or Extended BASIC ($8000-).
• Dragon 64 architecture additionally supports an alternate BASIC ROM.
• Cartridges can list up to two ROMs (e.g., for options like DOSDream resident from $E000).

Printers

• Printing to a file or via a pipe (e.g., through enscript) supported.
• Keyboard shortcut to flush output - useful when using a pipe.
• Dragon parallel port fully supported.
• CoCo & MC-10 printing only supported through ROM call intercept.

Other files

• DragonDOS or RSDOS binaries can be directly loaded into memory and executed.
• Similarly, Intel hex record format files can be loaded and executed.

SAM - 74LS783

• 4K, 16K and 64K RAM organisation all supported.
• Accurate simulation of video address counter - see SAM-VDG interaction.
• Accurate clock stretching on slow/fast transitions.

VDG - MC6847

• All Dragon/CoCo video modes supported, documented or not, due to implementing the SAM-VDG interaction.
• Supports original 6847 and the later 6847T1 with true lowercase.
• Optional external character generator supported (e.g., for Dragon 200-E).
• Accurate timing for PAL and NTSC Dragons and CoCo 1/2s.
• Accurate mode-switching, reflecting the timing differences between switching colour set and switching graphics mode, including many SAM video mode change side-effects.
• "Left over data" when switching modes part-way through a byte is good but not completely accurate yet.
• Font should be completely accurate now, thanks to research by Tim Lindner.

GIME - TCC1014

• Reasonable support for this CoCo 3 custom chip.
• Font should be completely accurate now, thanks to research by Tim Lindner.
• Differences between the 1986 and 1987 variants mostly represented.

CPU - MC6809

• Accurate down to which cycles are non-valid memory address and thus potentially affect the clock provided by the SAM.
• Deferred recognition of NMI, FIRQ, IRQ, latched NMI.
• HALT supported.
• Includes some of the behaviour recently uncovered by David Banks.

CPU - HD6309

• Implementation has matured with feedback.
• Division should now be accurate, thanks to Tim Lindner's 6309 fuzzing project.
• Needs review with respect to recent investigations by David Banks.

CPU - MC6803

• Supported for MC-10.
• Some illegal ops still need attention (though many are definitely ok).

PIAs - MC6821

• I/O behaviour based on internal sink/source plus external sink/source.
• Different behaviour for A-side and B-side.
• Interrupts recognised from Cx1.
• Cx2 as interrupt source implemented but untested.

Debugging

• Trace mode prints out each instruction after it is executed.
• GDB remote target support allows more interactive debugging. Use a specially patched GDB for 6809 support. Not implemented for the 6803 yet.