Commodore 128

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Commodore 128
C128 - The normal version breadbox
Type: Home Computer
Producer: Commodore
Price: 300 US$
Released: 1985
Discontinued: 1989
Memory: 128 KByte, upgradeable

The C128 home computer (known as the Commodore 128, CBM 128, and C=128) was Commodore’s successor to the C64. It functioned as a dual home/office computer and was 99% compatible with existing C64 programs. It featured two processors: an MOS 6502 variant and a Z80. The Z80 enabled it to run the industry standard CP/M operating system and software. The C128 had more free working memory than the C64, a built-in reset button, a numeric keypad, a machine code monitor, and a higher display resolution.

The C128 has three modes:

  1. BASIC 7: available after turning on the C128
  2. BASIC 2: C64 mode, available after entering GO64 or holding down the C= key at startup
  3. CP/M+ version 3.0: available after inserting and loading the CP/M system from disk drive

In 1986, Commodore introduced another model, the C128D, which integrated the C128 and 1571 floppy disk into a single desktop case. Both models will boot automatically from floppy disk. The C128D/C128DCR also featured a detachable desktop keyboard (all other C64/C128 models had a fixed keyboard).

Worldwide, Commodore sold around 4,500,000 units, with 284,300 units sold in Germany.

Construction[edit | edit source]

The C128 has following connectors, switches and interfaces:

Right side[edit | edit source]

Commodore 128 - right side
  1. Game port (Control port) 1; 9 pin Sub-D connector for connecting a joystick, light pen, mouse or paddles
  2. Game port (Control port) 2; 9 pin Sub-D connector for connecting a joystick, mouse or paddles
  3. Reset switch
  4. Power on/off switch
  5. Power connector (Power; 5 pin angular) for the power supply)

Rear[edit | edit source]

Commodore 128 - backside
  1. Main memory expansion (Expansion port; 44 pin; I/O) for connecting cartridges
  2. Cassette/Datasette port (Cassette port); 12 pin; I/O) for connecting a Datasette drive
  3. Serial bus interface or Serial Port (IEEE-488; 6 pin; I/O) for connecting disk drives or a printer
  4. Audio/Video connector (8 pin; I/O) for connecting a monitor/TV in 40 char mode,
  5. Antenna connector for connecting to TVs in 40 char mode (left of it: L-H for channel adjustment (optional)).
  6. RGBI connector (9 pin, output only) for connecting an RGB or monochrome monitor in 80 char mode.
  7. Userport (RS-232 or Centronics; 24 pin; I/O), which can be used by the C128 for connecting a modem or printer interface

Main board[edit | edit source]

  • Processor: HMOSII 8502 with about 1.02 or 2.04 MHz memory clock, Z80B processor 4 MHz version with 2.04 MHz clocked
  • Memory: 128 KByte RAM on two 64 KByte Chips (expandable internal on max. 256 KByte, external max. 640 KByte), from this are 38,911 or 122,365 Bytes free for use under BASIC
    • Picture frequency memory VDC-8563 (16 KByte video RAM)
    • Color memory 8564 (4×2 KByte)
Commodore 128 - Mainboard
  • ROM: 64 KByte, split:
    • C64 mode (16 KByte), Commodore BASIC V2.0 (8 KByte) and KERNAL (8 KByte)
    • C128 mode (64 KByte), Commodore BASIC V7.0 (48 KByte in 2×16 KByte Chips), KERNAL (16 KByte) and C128 BIOS (16 KByte)
    • CP/M BIOS (4 KByte)
    • Special character set NMOS-ROM (8 KByte)
    • Free connector for 32 KByte ROM (e.g. EPROM or additional character ROM)
  • Video:
    • The VIC-II or VIC-8564 for the 40 character mode has the ability for 25 (rows) × 40 (columns) characters (singlecolor and multicolor) in text mode (either big letters/graphic signs or big/small letters) or in graphic mode (HiRes) 320×200 pixel in 16 colors, 16 frame colors and 16 background colors or Multicolor mode (4 colors) 160×200 pixel, as well as 8 Sprites (singlecolor or multicolor, 24×21) displaying.
    • VDC-8563 for 80 character mode 25 (rows) × 80 (columns) with 16 colors, 8 character attributes, 16 frame colors and 16 background colors in text mode (either big letters/graphic signs or big/small letters) or in graphic mode (HiRes) 640×200 pixel singlecolor or 640×400 interlaced
Startscreen of Commodore 128
  • Audio: SID 6581/8580
    • Sound generator for three voices, 0-4 kHz
    • 4 wave forms per generator (Sine, Triangle, Pulse, Noise)
    • 3 amplitude modulators, 48dB
    • 3 ADSR envelope generators
    • Oscillator sync
    • Ring modulation
    • Programmable filters (low, band-pass, high-pass or notch filter)
    • Random generator
    • 2 connections for potentiometers
    • Audio inputs
  • Keyboard: 92 keys (QWERTY/QWERTZ), which are multiple reserved, with numeric keypad, German keyboard with DIN mode and

<ESCape>, <TAB>, <ALT>, <CAPS LOCK/ASCII+DIN>, <HELP>, <Line Feed>, <40/80-DISPLAY>, <NO SCROLL>, the Function buttons are predefined

  • Miscellaneous: 2 CIA-6526 for the I/O control (Input/Output), IC for memory management MMU-8722

Function Keys[edit | edit source]

The C128/D/DCR function keys are normally:

An overview or a modify of the function keys follows through the BASIC-command KEY in direct mode or in programs. After a reset or a reboot are the normally function key configuration active.

Links[edit | edit source]

WP-W11.png Wikipedia: Commodore_128