Read these specs and weep.
System
6502 8-bit CPU
3 Registers (A, X, Y), plus PC, SP, and flags.
56 Instructions
64K Address Space
64K RAM (available through banking out the following ROM's from the address space)
8K Basic ROM
8K Kernel ROM
Display
Character Map Mode
Each character is 8x8. The screen is made of 40x25 characters.
Character Set Source: ROM (predefined), or RAM (programmable)
Standard Character Mode: Any one color, or the screen background color
Multicolor Character Mode: Any one color, two pre-selected colors, or the screen background color
Extended Background Color Mode: Any two colors.
Bitmapped Graphics Mode
HiRes Mode: 320x200 pixels, any one color per character-cell, and the background color
Multocolor Mode: 160x200 pixels, 3 pre-selected colors, any one color per character-cell, and the background color
Sprites
8 sprites available, 24x21 pixels per sprite.
Standard Mode: Any one color overlayed on the background display.
Multicolor Mode: Any one color, plus 2 pre-selected colors overlayed on the background color.
Other Features
Smooth scrolling (both horizontal and vertical)
Selectable Display Border Color
Output
NTSC (to a TV)
Luma/Chroma (to a monitor)
Sound
3 voices mixed at one master volume.
Available waveforms
Sawtooth
Triangle
Square Wave
Noise Waveform
Envelope Control
Attack
Decay
Sustain
Release
Filtering
High-pass
Bandpass
Low-pass
Notch reject
Other Features
Vibrato
Ring Modulation
I/O
Built-in
Keyboard
Options
Cassette Drive
Floppy Disk Drives (5.25" - 1541/1571)
Hard Drives (MFM)
Joysticks (Atari 7-pin standard)
Cartridge Port (direct access to CPU bus)