A7800 vs Altirra

A7800 is a free, open-source Atari 7800 emulator and a fork of the MAME Atari 7800 driver. It runs on Android, Linux, macOS, and Windows; version 5.2 lists 64-bit x64 builds for Linux, macOS, and Windows. The emulator supports Proline and VCS joysticks, lightguns, paddles, driving controllers, keypads, Trak-Balls, Amiga mice, and ST mice. Its listed technical work includes improved MARIA DMA timing with accurate DMA-hole penalties, a RIOT emulation fix, POKEY sound changes, and SALLY and MARIA performance adjustments. Users can choose palettes and enhanced screen options. BIOS files are optional and not required. A7800 keeps MAME compatibility and syntax, allowing reuse of MAME configuration files and front ends. Developer targets can display DMA usage per scanline. The repository is offered under GNU GPL version 2 or later, and the license provides no warranty. The project labels v5.2 as its latest release, including corrections to the POKEY poly9 sequence and initial state.

Altirra is a Windows emulator for 8-bit Atari computers, covering the Atari 400/800, 1200XL, 600/800XL, 130XE, XEGS and 5200. It provides cycle-exact handling of documented hardware and models undocumented behavior, including DMA timing and undocumented 6502 instructions. Supported files include ATR, ATX, ATZ, DCM, XFD, PRO, ARC, BAS, ROM, BIN, A52, CAS and SAP. Reimplemented operating-system, BASIC and handler ROMs are included, while real Atari ROM images can be supplied for compatibility. The emulator models memory and cartridge expansions, PBI devices, modems and 65C02/65C816 accelerators. Disk options include accelerated loading, realistic timing, sounds and drive CPU emulation. Its debugger offers source stepping, breakpoints, watchpoints, history and profiling. Recording, a cheat trainer, disk browsing and text copy/paste are also included. Altirra is free under GPL version 2 for Windows 7 or later.