The Atari 7800 ProSystem, or simply the Atari 7800, is a video game console re-released by Atari Corporation in January 1986. The original release had occurred two years earlier under Atari Inc. The 7800 had originally been designed to replace Atari Inc.'s Atari 5200 in 1984, but was temporarily shelved due to the sale of the company after the video game crash. In January 1986, the 7800 was again released and would compete that year with the Nintendo Entertainment System and the Sega Master System. It had simple digital joysticks; it was almost fully backward-compatible with the Atari 2600; and it was considered affordable at a price of US$140.
In 2009, IGN chose the 7800 to be their 17th best video game console of all time.
Specification from Wikipedia:
CPU: Atari SALLY 6502 ("6502C")
Speed: 1.79 MHz, drops to 1.19 MHz when the TIA Television Interface Adaptor or RIOT (6532 RAM-I/O-Timer) chips are accessed
(note: Unlike a standard 6502, SALLY can be halted to allow other devices to control the bus)
RAM: 4 KB (2 6116 2Kx8 RAM ICs)
ROM: built in 4 KB BIOS ROM, 48 KB Cartridge ROM space without bankswitching
Graphics: MARIA custom graphics controller
160x240 (160x288 PAL) resolution or 320x240/288 resolution
25 color palette out of 256 colors (16 hues * 16 luma), different graphics modes restricted the number of usable colors and the number of colors per sprite
Direct Memory Access (DMA)
Graphics clock: 7.16 MHz
I/O: Joystick and console switch IO handled byte 6532 RIOT and TIA
Ports: 2 joystick ports, 1 cartridge port, 1 expansion connector, power in, RF output
Sound: TIA video and sound chip, same as the 2600. Only the sound is used in 7800 games. Both video and sound are used in 2600 games.
Optional POKEY sound chip on cartridge for improved sounds