Commodore VIC-20

Commodore VIC-20

Commodore VIC-20 – The Friendly Computer
Specifications
Manufacturer	Commodore Business Machines
Type	Home Computer
Released	1980 (Japan), 1981 (Worldwide)
Discontinued	January 1985
Intro price	US$299.95 (1981)
CPU	MOS Technology 6502 @ 1.1 MHz (PAL) / 1.02 MHz (NTSC)
Memory	5 KB RAM (3.5 KB usable), expandable up to 32 KB
Storage	External cassette tape (Datasette), optional 5.25" floppy disk drive
Display	176×184 pixels, 22×23 text characters, 16 colors
Sound	3 square wave generators + 1 noise channel (mono)
Dimensions	40.3 cm × 20.4 cm × 7.2 cm
Weight	1.8 kg
OS / Firmware	Commodore BASIC 2.0 (in ROM)
Predecessor	Commodore PET 4000 Series
Successor	Commodore 64
Codename	VIC-20, VC-20 (Germany), VIC-1001 (Japan)
Model no.	VIC-1001, VIC-20, VC-20

The Commodore VIC-20 was a groundbreaking home computer introduced by Commodore Business Machines in 1980. Known as the VIC-1001 in Japan and the VC-20 in Germany, it was the first computer to sell over one million units, making computing accessible to the masses.

🧠 Architecture and Processor

At its core, the VIC-20 utilized the MOS Technology 6502 8-bit microprocessor, operating at 1.1 MHz for PAL systems and 1.02 MHz for NTSC systems. This CPU was also employed in other notable systems like the Apple II and Commodore 64.

💾 Memory and Storage

The VIC-20 came with 5 KB of RAM, with approximately 3.5 KB available for user programs. Memory could be expanded up to 32 KB via external cartridges.

For storage, the VIC-20 relied on external devices:

• Datasette – a cassette tape drive for loading and saving programs.
• VIC-1540/VIC-1541 – optional 5.25" floppy disk drives connected via the serial port.

🖥️ Display and Graphics

The VIC-20 featured a 176×184 pixel resolution with a text display of 22 columns by 23 rows. It supported a palette of 16 colors. Graphics were character-based, and while it lacked a bitmap mode, users could define custom characters for simple graphics and animations.

🔊 Sound Capabilities

Sound was generated through the MOS Technology VIC chip, offering:

• Three square wave generators.
• One white noise generator.
• Overall volume control.

These features allowed for basic music and sound effects in games and applications.

🎮 Input/Output and Expansion

The VIC-20 was equipped with several I/O ports:

• Cartridge Port – for software and memory expansion cartridges.
• User Port – for modems and user-designed peripherals.
• Serial Port – for printers and disk drives.
• Joystick Port – compatible with Atari-style joysticks.
• Cassette Port – for the Datasette.
• RF and Composite Video Outputs – for connection to TVs and monitors.

🧰 Maintenance and Upgrades

Common maintenance tasks for the VIC-20 include:

• Cleaning the keyboard contacts to address unresponsive keys.
• Checking and replacing aging capacitors to prevent power issues.
• Ensuring proper alignment of the Datasette for reliable data loading.

Upgrades could be performed via the cartridge port, including memory expansions and software cartridges.

📚 Technical Documentation

For detailed technical information, refer to the following resources:

• Commodore VIC-20 Technical Manual
• Commodore VIC-20 Programmer's Reference Guide
• Commodore VIC-20 User Manual

📷 Gallery

• Front view of the Commodore VIC-20
  Front view of the Commodore VIC-20
• Rear panel showing I/O ports
  Rear panel showing I/O ports
• Internal motherboard layout
  Internal motherboard layout
• Datasette cassette tape drive
  Datasette cassette tape drive

🧪 Related Pages

• Commodore VIC-20 Maintenance Guide
• Commodore VIC-20 Troubleshooting Guide
• Commodore VIC-20 Keyboard Repair Guide
• Commodore VIC-20 Capacitor Replacement Guide