Games - Commodore 128

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	Games - Commodore 128

The Commodore 128 (C128, CBM 128, C=128) home/personal computer was Commodore Business Machines (CBM)'s last commercially released 8-bit machine. Introduced in January of 1985 at the CES in Las Vegas, it appeared three years after its predecessor, the bestselling C64.

Technical overview

The C128 was a significantly expanded, and compatible, successor to the earlier C64, the new machine featuring 128 kB of RAM (externally expandable to 640 kB) and an 80-column RGB monitor output (driven by the 8563 VDC chip with 16 kB dedicated video RAM), as well as a redesigned case/keyboard with a numeric keypad. Instead of the 6510 CPU of the C64, the C128 incorporated a two-CPU design. The primary CPU, the 8502, was a slightly improved version of the 6510; its main addition was the ability to run at a 2 MHz clock rate (however, this required turning off the 40-column video output). The second CPU was a Zilog Z80 and had the only purpose of ensuring CP/M compatibility.

The C128 had three modes of operation: C128 Mode (native mode), which ran at 1 or 2 MHz with the 8502 CPU and had both 40- and 80-column text modes available; CP/M Mode, which used the Z80 second CPU in either 40- or 80-column text mode; and C64 Mode, which was very nearly 100% compatible with the earlier computer.

C128 Mode

While the C64's graphics and sound capabilities were generally considered excellent, the popular home computer was the subject of a number of perennial criticisms. The 40-column VIC-II video display, while excellent for gaming, was often considered inadequate for productivity applications such as word processing. The lack of a numeric keypad was also an issue with some office suite software. Furthermore, the 2.0 revision of Commodore BASIC that was incorporated into the C64 was quite limited, and lacked keywords to handle the system's graphical and sound capabilities; these features had to be accessed via cumbersome PEEK and POKE commands. Some programmers also criticized the lack of a hardware reset button. Finally, the C64's 1541 disk drive was almost universally condemned as slow and unreliable.

The designers of the C128 succeeded in rectifying most of these concerns. A new chip, the VDC, provided the C128 with an 80-column color RGB display. The new 8502 CPU was completely backward-compatible with the C64's 6510, but could run at double the speed if desired. A numeric keypad was added to the keyboard, as were various other keys. The C64's rudimentary BASIC 2.0 was replaced with the far more flexible and powerful BASIC 7.0, which included keywords designed specifically to take advantage of the machine's capabilities, and also incorporated a sprite editor and machine language monitor. The screen editor was further improved. A reset button was added to the system. Two new disk drives - the single-sided 1570 and double-sided 1571 - were introduced in conjunction with the C128, promising far faster transfer speeds via a new "burst mode". The C128 also had far more RAM than the C64, and a far higher proportion was available for BASIC programming, due to the new MMU bankswitching chip.

The C128's greater hardware capabilities, especially the increased RAM, screen display resolution, and serial bus speed, made it the preferred platform for running the GEOS graphical operating system.

CP/M Mode

The second of the C128's two CPUs was the Zilog Z80, which allowed the C128 to run CP/M; the machine came with CP/M 3.0, aka CP/M Plus (backward compatible with CP/M 2.2) and ADM31/3A terminal emulation. To make a large application software library instantly available at launch, the Commodore 128 CP/M and accompanying 1571 floppy disk drive was designed to run almost all Kaypro-specific CP/M software without modification.

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Games - Commodore 128

Technical overview

C128 Mode

CP/M Mode

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