Atari++
The Atari++ is a free, open source portable cycle accurate Atari 5200 Emulator. Like many other Atari 5200 emulators, this supports Atari’s whole assortment of 8-bit computers.
These 8-bit computers being the Atari 400 and 800, the Atari 400XL, 800XL and 130XE. The emulator is auto-configurable meaning the user will not have to play around with settings to get the emulator running correctly.
Atari++ features many advanced features, such as being cycle accurate which allows the software to successfully replicate the Atari 5200 and other systems as if it was running on the system itself.
This means the program also successfully emulates even the bugs found in the original system, which can be a key to emulating certain games and applications that use advanced techniques.
Atari++ has a particular focus on achieving emulation that is as close to the original system as possible, and for that it does it extremely well.
It manages to successfully emulate both the sound chip of the systems and the processors. Like most Atari 5200 emulators, it is extremely capable of emulating the system, and you cant go wrong with using Atari++ as your core emulator for those systems.