4.10-test12 / 09-05-2022






Altirra is a full cycle-exact emulation of all documented hardware features for the Atari 400/800, 1200XL, 600/800XL, 130XE, XEGS, and 5200 systems and is particularly notable for having a very well equipped debugger tool.


Windows: XP SP3+ for x86/x64

                     Qualcomm Snapdragon 835+ for ARM64

  • Adds initial support for the ComputerEyes Video Acquisition System.

  • Fixes H6-H9: not supporting append mode.

  • Fixes very long delays or garbled instruction readouts when toggling the collapse modes in the history pane.


  • Fixed incomplete banking setup for 5200 Super Cart in 128K and 256K sizes.


  • Improved Keyboard Shortcuts dialog to be more reliable at binding Alt+key combinations.

  • Shortened and adjusted timing offset light pen/gun trigger pulse to be more realistic.

  • Split light pen/gun controllers apart so they have different offsets and to get rid of the inversion on the pen switch. Existing input maps need to be remade to take advantage of this.

  • Removed extraneous secondary button from light pen/gun controllers.

  • Added light pen noise emulation.


  • Adds support for DXGI 1.3 seamless custom refresh rates, which can be enabled in Tools > Options > Display. There are narrow circumstances in which this works: you need Windows 8.1 or newer and both a video driver and internal LCD panel that supports appropriate custom refresh rates, with no external displays connected, and running borderless full screen. When this works, the emulator can switch the LCD panel to 50Hz for smooth PAL operation even if the display doesn't normally report 50Hz as a supported refresh rate. Unfortunately, Windows doesn't provide usable ways to determine when a custom refresh rate actually takes effect, so this can only be verified visually.

  • Fixed a possible crash when scaling up in the video recorder.

  • Added a bunch of advanced debug config vars for the display code.

  • The D3D11 driver now displays some vsync timing information and composition mode when debug info is enabled.

  • Fixed light pen/gun vertical position being way off in PAL. As a result of this fix, the light pen/gun offset has been reset in 4.10-test9 to be separate from previous versions. (0,0) is now an average-ish position for some XEGS light gun games.

  • Added a command to recalibrate the light pen/gun offset. Unlike the dialog settings, this is interactive where you can click on where the emulated program thinks the light pen/gun position is, and the emulator will auto-compute the offset adjustment based on that.

  • The immediate paddle option now also enables immediate light pen/gun updates, which can also remove 1 frame of latency for light pen/guns.

  • Some internal code reorganization to improve building of the RMT plugins, removing some more extraneous dependencies and formally relicensing the remaining ones. The RMT plugins and the libraries used in them are now GPLv2 with an explicit linking exception for noncommercial use. This additional exception is retroactive. See COPYING.RMT in the source archive for details. Note that there is no functional change in the RMT plugins in this version.

  • YASM has been removed as a build dependency.

A few misc notes:

  • This version contains some pre-work on trying to reduce latency, but the WIP was not stable enough to release yet. One thing I discovered is that some night light reduction programs, notably f.lux, can introduce an extra frame of latency in full-screen mode. This is because the default settings for that program force the DWM to composite. You can tell if this is happening if the D3D11 debug info says that the composition mode is [Composed: Flip] instead of [Hardware: Independent Flip].

  • Multiple monitors can also cause additional latency in windowed mode. With two monitors, the Windows 10 DWM will sometimes lose track of the flip queue and queue more than one frame, raising the minimum latency to 2+ frames. Also, in some cases it cannot promote a window to hardware overlay if two monitors are active.

  • The light pen calibration screen in the Atari Graphics cartridge is somewhat difficult to get past because it has a strict limit on the PENH values it will accept, and as a result it will not accept the calibration positioning unless you either aim left of it or set the offset negative. I suspect that this is because the Atari light pens have a different horizontal offset than light guns, but need to get data from an actual light pen to verify. If this is the case, I'll need to put in a separate offset for light pens.


  • Fixed an issue with cassette audio sometimes desyncing after an accelerated C: load.

  • Added support for CAR types 71-75. Special thanks to the Atari800 development team for confirming that it was OK to use info from their carts.txt file that hadn't been published in a release yet.

  • The Check For Updates dialog now has a link to the internal RSS update feed.

  • The Memory pane in the debugger now supports editing memory.

  • Warp now starts instantly when in slow motion, rather than only on next frame.

  • Added a config var for the slow motion speed ratio.

  • Fixed Unicode mappings in disk explorer text viewer.

  • Copy/paste now supports the international character set, and the default layout now maps international characters to their Ctrl+key equivalents.

  • Added XE Multicart support.


  • Additions: Fixed LOADEXE.XEX using old $FD device SIO code for the program loader instead of $7D.

  • AltirraOS: Fixed math pack compatibility issue with FDIV modifying FLPTR (fixes B-Graph pie chart routine).

  • AltirraOS: Fixed a cursor position checking bug with split screen Gr.0 (fixes the BASIC game House of Usher).

  • AltirraOS: Fixed compatibility issue with KEYDEL handling (fixes cursor movement in BrushupV40).

  • ATBasic: IOCB#7 is now automatically closed on I/O errors to avoid SAVE files being kept open for write.

  • Cassette: Fixed FLAC decoder crash with some block sizes.

  • Cassette: Fixed regression with FSK blocks in CAS files being read as turbo pulses instead of FSK pulses.

  • Disk: Retuned XF551 high-speed C/E to data frame delay.

  • Display: Workaround for D3D11 minimum precision crash on Intel Iris Xe driver.

  • Serial: Pad out 850 relocator to match length of original firmware relocator (fixes compatibility with loaders that hardcode the relocator length).

  • VFS: Fixed wrong file being accessed when using atfs:// paths to access files inside a DOS 2 disk image.


  • Compiler changed to Visual Studio 2022.

  • AltirraOS: Improved compatibility of KEYDEL handling.

  • Custom Devices: Script compiler now parses and blocks ++ and -- operators to prevent them from being parsed as pairs of unary operators.

  • Debugger: Fixed memory window horizontal scroll bar.

  • Devices: Lifted internal PIA limit which could cause devices to break in unusual cases with too many devices connecting to the PIA inputs.

  • Display: Retuned monochrome artifacting fix to high artifacting filter to restore comparable quality of color modes to 4.00.

  • Display: Fixed broken text after toggling HDR on the fly.

  • PCLink: Directory enumerations now report if the directory is root or a subdirectory.

  • PCLink: Improve compatibility of path parsing compared to base SDX filesystem.

  • Tape: C‌: SIO patch is now more flexible in handling of the transfer mode byte.

  • Tape: Improved quality of tape resampler.

  • Tape: Fixed incorrect rate handling of pwml chunks in CAS files.

  • Tape editor: Fixed store waveform option not actually doing anything.

  • Tape editor: Added Copy Decoded Data command.

  • Tape editor: Restored previous version of FSK decoding so that there are both now block-oriented and freeform decoders.


  • Fixed bugs with monochrome modes not working with VBXE or high artifacting modes. Unfortunately this fix also results in the return of some chroma artifacts in NTSC high artifacting mode that were previously being incorrectly canceled; I may try to retune the artifacting filters again at some point.

  • Tape editor: fixed broken CAS saves after some edits, highlight and scroll to changes on undo, add menu option and shortcut to re-run decoding analysis after doing an edit, redo FSK decoding in the tap editor to be closer to regular emulation decoding to increase reliability, shift+click now only moves the endpoint of the selection, warn when standard blocks will be converted to FSK on CAS save, and optimize FSK blocks on save.

  • C: SIO patch now supports disabling the timeout with DTIMOT=0, which fixes some tapes that had extremely long blocks (>4.5 minutes).

  • Added support for loading PWM-encoded chunks in CAS files.


  • Fixed crash with loading some FLAC files.

  • Accelerated C: loads now properly leave tape running after block load. This fixes some tape loaders that mix C: loads and custom tape routines.

  • Fixed regression with FSK pulse blocks in .CAS files being loaded as turbo data instead.

  • Improved frame rate stability with windowed vsync in D3D11 mode on Win8.1+.

  • /startuplog: now allows disabling log channels and blocks Ctrl+C.

  • C: patch can now load blocks longer than 30 seconds. (There are tapes with single blocks that are minutes long.)

  • Tape editor: fixed draw tool with waveform displayed, SIO capture option now shows enabled state, accelerated C: loads show sync bytes, and block checksum status displays more reliably during live captures.


  • VFS: Fixed off-by-one error when accessing files on a DOS 2 image using the atfs:// prefix.

  • ATBasic: IOCB#7 is now automatically closed on I/O errors to avoid SAVE files being kept open for write.

  • Disk: Retuned XF551 high speed C/E to data frame delay based on firmware timings.

  • Additions: Fixed incorrect device ID in loadexe.xex.

  • HLE: "Disk boot" program load mode now simulates an SDFS disk to trigger the EXE load under SDX.


  • The device tree now better preserves selection when adding or removing devices.

  • AltirraOS updated to 3.32 with fixes for a couple of compatibility issues with the math pack, so B-Graph and House of Usher now work.

  • Fixes to the docking UI to reduce glitching when switching layouts or toggling full screen mode, due to panes becoming visible too soon and drawing in weird places before being moved to their final location.

  • Fixed a few timing bugs in the standard disk emulator. 810s now produce the head bump sound, the timeout was too short for Record Not Found (RNF) errors, and with long retries the idle timeout was sometimes kicking in too soon. Happy 810 and 1050 now have retuned receive rates.

  • The standard disk emulator now attempts to emulate track buffering for the Happy 810, 1050, and Speedy 1050 profiles, where the drive will burst transmit sectors from memory after reading in new tracks. This makes timing closer to the default modes for those drives. The Happy 1050 commands for toggling track buffering are now also support.

Nothing Additional to add...