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4.20-test7 / 14-03-2023





average rating is 4.1 out of 5
average rating is 4.1 out of 5
average rating is 4.6 out of 5

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


  • Math pack symbols can be unloaded separately in the debugger to avoid conflicting with PBI firmware.

  • Added static trace PBI (stp) command.

  • Fixed basic block detection when disassembling 8048 code.

  • Fixed a bug with bogus $01 banks showing up in 8048 mode.

  • Fixed data bank showing up with PEI (dp) indirection preview.

  • Added option to reinterleave floppy disks at 2:1.

  • Added firmware detection for the two known versions of the 1400XL V:/T: firmware.

  • Added support for drive/side selection on 1450XLD drive, and workaround for boot sector encoding issue


  • Initial 1400XL/1450XLD emulation.

  • Pad input area for tablet/powerpad can now be moved and resized in Configure HUD.

  • 65C816 fixes for PLB/PLD flag handling, PHP bits 4/5 after returning to emulation mode, incorrect stepping outside of bank 0, and some stack wrapping bugs specific to the Veronica '816.

  • Fixed XF551 write protect handling and improved FDC read/write timing.

  • The Reinterleave option in the Disk Drive dialog now marks the disk as modified.

  • AltirraOS updated to 3.35 with a bug fix for incorrect MEMLO handling when loading CIO handlers via type 4 polls.

  • Added PHLOAD.COM to Additions disk to trigger type 4 polling and peripheral handler loads.

  • Debugger: 'bta' command can now be used without a trace string; a default one is provided.


  • Debugger: (dp), (dp,X), and (dp),Y addressing modes now also suppress symbol lookup for non-zero D register, and there is now an option in the Disassembly window to control this behavior.

  • Horizontal and vertical mouse scrolling can now be bound in input maps. In particular, this allows two-finger panning on Precision Touchpads for uses like paddles.

  • Corrected the input map generator not binding mouse inputs for some light pen/gun types.

  • Added an option to draw touch points for pad/gun controls. In particular, this allows seeing the current touch point when driving such a control with a non-mouse input or when multi-touch input is involved.

  • Added emulation support for the Chalk Board PowerPad controller.


  • Another attempt to fix the downmix setting. It now also disables in mono.

  • PEI (dp) no longer shows deref value.


  • Display pan/zoom capability added.

  • Fixed some bugs in the D3D11 display path with GPUs that require power of two sized textures.

  • Fixed stereo-as-mono setting not saving.


  • VBXE blit logging uses beam tagged logging again.

  • Command line parsing changed for better consistency: switches now must be separate arguments and are no longer allowed combined with other switches or arguments, e.g. "test.atr/s/f" must now be "test.atr /s /f".

  • Added special:// protocol to access some internal images, including special:// to bind to current default BASIC cartridge.

  • Added support for enhanced Deflate (a.k.a. Deflate64(tm)) in .zip files.

  • The currently selected output is saved in save states when multiple outputs are active (i.e. XEP80).

  • Added MIO save state support.

  • Fixed an MIO issue with initial interrupt state that could cause a hang at boot.


  • Save state rework:Added Covox, R-Time 8, U1MB, VBXE, and XEP80 save state support.
    Added partial SIDE 1/2, SIDE 3, MyIDE, and BlackBox save state support. Save states will not work if saved during a disk transfer; there is now a warning if a save state is attempted during one.
    Axlon and 65C816 high (linear) memory are now saved.
    Fixed a bug with SKSTAT not being saved properly, which caused stuck keys.
    Fixed some extended memory not saving properly in 128K and 320K modes.
    Fixed DP register not being saved in 65C816 mode.
    Added thumbnails to save state files. They are not used in the emulator yet, however.

  • Updated file association registration:The placeholder app registration created by Explorer is removed on registration to get rid of the duplicate app entry.
    Fixed an issue where the Windows shell might not be updated immediately after changing file type registrations.
    There are now command-line switches to have the emulator register or unregister file types in silent mode.
    Added a dialog explaining how to navigate the brain-dead Windows 10/11 Default Apps settings UI.

  • Debugger: It is now possible to escape a symbol name that starts with @, e.g. #@current.

  • Debugger: VBXE blit logging/dumping now has a compact display mode, and the .vbxe_bl command can now dump a blit list at any local address.

  • Debugger: Zero page addresses are now loaded from CC65 debug info.

  • Cassette: Added data-as-audio playback support for raw FSK and PWM blocks in .cas files. There are some harmonics from turbo tapes when doing this due to jitter from the 10KHz resolution in raw .cas blocks which appears hard to filter out; Altirra's internal tape precision is 31KHz but a pulse adjustment pass would be needed to take advantage of that.

  • Input: Fixed POT lines being grounded improperly when binding a digital (binary) input to the analog paddle knob.

  • Cartridge: Fixed the Phoenix and Blizzard cartridge types to also disable the cart on CCTL reads.

  • Cartridge: Added support for the Williams 16K cartridge type.

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