Altirra, an 8-bit Atari computer emulator v4.20

Emulates the Atari 400/800, 1200XL, 600/800XL, 130XE, XEGS, and 5200 systems.
Full, cycle-exact emulation of all documented hardware features.
Best-in-class emulation accuracy of undocumented hardware behavior, including undocumented 6502 instructions, precise DMA timing, mid-screen register changes, hardware bugs, and cycle-precise timer IRQs.
Support for most popular 8-bit image file formats: ATR, ATX, ATZ, DCM, XFD, PRO, ARC, BAS, ROM, BIN, A52, CAS, SAP.
Contains reimplemented versions of OS, BASIC, and handler ROMs to run 8-bit software with high compatibility without needing Atari ROMs.
Emulation of over three decades of hardware expansions, including memory expansions, cartridge expansions, Parallel Bus Interface (PBI) devices, modems, and 65C02/65C816 accelerators.
Accurate emulation of multiple disk drive types with options for accelerated disk loads, realistic disk timing, drive sounds, and full drive CPU emulation.
Flexible display with Direct3D 9/11 acceleration, aspect ratio options, easy resizing, and artifacting support.
Audio and video recording, cheat trainer, DOS disk explorer with drag-and-drop, and text mode copy/paste.
Powerful debugger with label decoding, source-level stepping, conditional breakpoints/tracepoints, watchpoints, execution history with loop/call/interrupt folding, and profiling.
Native Windows UI with theme support, per-monitor high DPI support, file associations, drag and drop, copy/paste, and DirectInput/XInput controllers.
32-bit (x86), 64-bit (x64), and ARM64 versions available.