Custom 6502c CPU (Sally, not 65c02) at 1.79 MHz, (90% bus availability) Custom graphics chip with 7.16 Mhz pixel clock, Custom 2600 compatible sound chip, 4K RAM (mostly for video display with resolution of 320x242, 16 colours from 256 colour palette, and 64 sprites), up to 52K ROM or more with bank-switching, Design allows cartridges to include additional hardware such as a sound chip, as used in "Ball Blazer".
(Other people claim the 7800 has 8K RAM, and takes 64K cartridges.)
Atari 7800 console +PSU, 240v UK (PAL) or 110v US (NTSC)
7800 Accessories
Official Atari Accessories
Atari 7800 Controllers (joypads shipped in UK)
Atari 7800 Pro-Controllers (special joysticks)
Atari 7800 Light-Gun (Atari XE ones work too)