Commodore 128

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The Commodore 128 (C128, CBM 128, C=128) home/personal computer was the last 8-bit machine 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 primary hardware designer of the C128 was Bil Herd.


Technical overview

The C128 was a significantly expanded successor to the C64 and unlike the earlier Plus/4, nearly full compatibility with the C64 was retained. The new machine featured 128 KB of RAM, in two 64 KB banks and an 80-column RGBI video output (driven by the 8563 VDC chip with 16 KB dedicated video RAM), as well as a substantially redesigned case and keyboard, which included four cursor keys (previous Commodores had two, which required using the shift key to move the cursor up or left), an Alt key, Help key, Tab key (not present on prior models) and a numeric keypad. Many of the added keys matched ones present on the IBM PC's keyboard. While the 128 still had a 40 column mode, an extra 1K of color RAM was made available to the programmer, as it was multiplexed through memory address 1. The 128's power supply was vastly improved over the 64's unreliable design, being larger and equipped with cooling vents and a replaceable fuse. Instead of the single 6510 microprocessor of the C64, the C128 incorporated a two-CPU design. The primary CPU, the 8502, was a slightly improved version of the 6510 capable of being clocked at 2 MHz. The second CPU was a Zilog Z80 which was used to run CP/M software, as well as to initiate operating mode selection at boot time. The two processors could not run concurrently, thus the C128 was not a multiprocessing system.

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