MOS Technology TED

Lore & Background

The TED was designed for the Commodore 16 and Plus/4, providing video capabilities largely a subset of the VIC-II. It supported five video modes, including text and graphics modes, but lacked sprites, forcing game animation to use custom character sets. The TED included two features the VIC-II lacked: luminance control and blinking text. It generated 16 base colors via Pb and Pr chroma signals, with 8 possible luma steps, yielding a palette of 121 YPbPr colors, some out of RGB gamut.

Sound capabilities were limited to a simple tone generator with two channels: one square wave and one that could produce square wave or white noise. The chip also contained three 16-bit interval timers, a raster register for IRQ generation, and an I/O port for controlling the IEC bus and Datassette. The TED had higher DRAM access priority than the CPU, throttling the CPU to half speed in the active display area.

The chip was known for a tendency to destroy itself through overheating, and improved cooling is recommended. As TED chips are no longer produced, its architecture was replicated by Hungarian developer Istvan Hegedus using Verilog HDL in the open-source FPGATED project, leading to a C16 implementation on MiSTer and a working drop-in replacement. Another replacement, the ThED project, was put on hold due to component supply difficulties.

Reader's Guide

The TED's significance lies in its integration of multiple system functions into a single chip, reducing component count for the Commodore 16 and Plus/4. Its luminance control allowed a wider color range than the VIC-II, though the lack of sprites limited graphical complexity compared to the Commodore 64. The chip's overheating issue is a notable drawback, and its discontinuation has driven open-source replication efforts. The FPGATED project by Istvan Hegedus provided a Verilog HDL implementation, enabling FPGA-based replacements and preservation of these computers. The ThED project attempted a similar replacement but stalled due to component supply issues. The TED's legacy is thus tied to both its role in budget Commodore machines and the community efforts to keep those machines operational.

Did You Know?

• The TED lacked sprite capabilities, unlike the VIC-II, which used two thirds of its die area for sprites.
• The TED could display 121 YPbPr colors, with some colors marked as out of the RGB gamut.
• The chip had a known tendency to destroy itself through overheating, requiring improved cooling.
• The TED's internal architecture was replicated in Verilog HDL by Hungarian developer Istvan Hegedus in the open-source FPGATED project.