• Type: Home computer
  • Released: January 1985
  • Discontinued: 1989
  • Units sold: 4-5.7 million
  • OS: Commodore BASIC 7.0, Commodore BASIC 2.0, Digital Research CP/M 3.1 (3.0 in Commodore marketing)
  • CPU: MOS 8502 @ 2 MHz, Zilog: Z80 @ 4 MHz
  • Memory: 128 KB RAM, 2 KB color RAM (for the VIC-II E), 16 KB or 64 KB video RAM (for the VDC), up to 512 KB REU expansion RAM
  • Graphics: VIC-II (320×200, 16 colors, sprites, raster interrupt), MOS 8563 (RGBI 640×200i 16 colors programmable (640x400i and 800x600i possible), blitter)
  • Sound: SID 6581/8580 (3 channels)
  • Predecessor: Commodore 64 (C64 outlived C128)
  • MMU: MOS Technology 8722
  • ROM: 72 kB
  • I/0: All C64 ports plus higher speed possible on the serial bus, expansion port more flexibly programmable, RGBI video output (DE9-connector) , External keyboard input (DB25-connector) (C128D(CR) only)

Released 1985: The Commodore 128, also known as the C128 or occasionally CBM 128, is the last 8-bit home computer commercially released by Commodore Business Machines (CBM). Introduced in January 1985 at the CES in Las Vegas, it appeared three years after its predecessor, the bestselling Commodore 64.

The C128 is an significantly expanded successor to the C64, with nearly full compatibility. The newer machine has 128 kB of RAM in two 64 kB banks, and an 80-column color video output. It has a redesigned case and keyboard. Also included is a Zilog Z80 CPU which allows the C128 to run CP/M as an alternative to the usual Commodore BASIC environment. The presence of the Z80 and the huge CP/M software library it brings, coupled with the C64’s software library, gives the C128 one of the broadest ranges of available software among its competitors.

List of Commodore 128 commercial software >>>

CP/M operation mode
CP/M was a mass-market operating system created for S-100 bus based computers with Intel 8080/85 or Z80 processor. It was an early industry standard for microcomputers and was widely used in business through the late 70’s and into the mid-80’s. CP/M also was the planned operating system for the IBM PC and was optional instead of PCDOS with the first IBM PC model.

C128 has a Z80 CPU running at 4 MHz in CP/M mode. Because it’s “sharing RAM with the VICII chip” it’s equal to only about 3 MHz. The same goes for the Z80 CP/M cartridge for Commodore 64, which I’m happy to have in my collection as well.

CP/M is a disk intensive operating system. The 1571 floppy drive that was launched with the C128 and is integrated in the C128D and C128D-CR take advantage of the faster serial bus (IEC) in the C128. This helps performance in CP/M. Speed will also increase a significantly by using “unofficial” CP/M builds wish are optimized from Z80 assembler code. Later C128 CP/M bundled versions also supports the REU RAM expansion as a bootable RAM disk.

Programs written for CP/M were normally compatible among different machines, but contrary to MS-DOS, there were extremely many floppy formats as each computer manufacture typically had their own format. The software publishers had to make many master disks in different formats for the same program, even the program itself was compatible. Luckily, the 1571 drive is able to read a wide range of floppy formats, “Jugg’ler 128” is a program that reads more than 140 different formats, including MSDOS disks.

C64 operation mode
More than 10 000 commercial games and software titles are released for the C64, while only a few games were released especially for the C128. Many owners used their C128 solely as a C64 because of this. C128 is almost 100% both software and hardware compatible with the C64.  For those not familiar with the C64, it’s regarded as the best selling computer of all time with about 17 million units sold. Production of C64 continued on until close up to the demise of Commodore in 1994, and outlived it’s successor the C128.  Even the C128 was meant as a successor, the C64 remained very popular and price was reduced during the years.

My Commodore 128, repair and upgrade: When I first got it, programs where freezing in C128 mode at the same places, machine was working outer wise. This symptom could indicate a faulty RAM chip (stuck BIT in chip). I located the faulty chip using the “piggy back” method where I carefully put a new chip on top of the old chip. When I found it I soldered in a new chip. The C128 was working again.

I’ve also updated both my C128’s to 64 KB video RAM later (The C128D-CR has 64 KB video RAM originally) for the VDC chip (80 column display). The normal C128 (flat) and the C128D both has 16 KB of video RAM originally as the 80 column display initially was only intended for text display. All C128’s can easily be updated to 64 KB video RAM.

List of Commodore 128 commercial software >>>
Commodore 128

Remi Jakobsen

I'm collecting classic computers and video games, stretching from the 70's into the 90's. Restoration, history, usage ...

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