MOS Technology 8563

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The 8563 Video Display Controller (VDC) was an integrated circuit produced by MOS Technology. It was used in the Commodore 128 computer to generate an 80-column (640×200 pixel) RGB video display. The D/DCR models of the C128 used the later 8568 [D]VDC chip.

History and characteristics

The VDC was designed with office suite applications in mind. Shown here is SpeedScript 128, a word processor.

This Ultra Hi-Res demo showcases the VDC's blitter capabilities with a simple 3D animation of a wire frame model of a cube.

Originally intended for a planned (but unreleased) UNIX-based business computer, Commodore designed the VDC into several prototype machines. Of these, only the Commodore 128 ever saw production. Unlike earlier MOS video chips such as the popular VIC-II, the VDC had its own dedicated RAM, rather than sharing the main system memory. The chip was more difficult to produce than most of the rest of the MOS line, and initial yields were very low. [link]

Officially, the VDC was a text-only chip. BASIC 7.0, the Commodore 128's built-in programming language, only supported high-resolution graphics in 40-column mode via the legacy VIC-II chip. However, the VDC did in fact include a high-resolution bitmap mode, which was quickly discovered by hackers. In February 1986, less than a year after the Commodore 128's release, RUN magazine published "Ultra Hi-Res Graphics", an article describing the VDC's bitmapped mode and including a type-in program (written in 8502 assembly language) that extended BASIC 7.0's capabilities to support 640×200 high-resolution graphics using the new chip. [link] Author Lou Wallace further developed the Ultra Hi-Res utility into a commercial package, BASIC 8. One of the most popular third-party utilities for the C128, this offered more advanced VDC high-resolution capabilities to a wide audience of programmers.

Commodore finally offered complete official documentation on the VDC in the Commodore 128 Programmer's Reference Guide. VDC bitmap modes were used extensively in the Commodore 128 variant of the GEOS operating system.

The VDC lacked sprite capabilities, which limited its use in gaming applications. However, it did contain blitting capabilities to perform automatic block memory copies from system RAM to video RAM.

Technical specifications

• 16 or 64 KB address space for screen, character and color memory (dedicated, separate from system memory)
• 640×200 pixel video resolution (640×400 in interlaced mode)
• 80×25, 80×50, 40×25 characters text resolution
• 16 colors

External links

• [Ultra Hi-Res self-extracting archive - Volume I]
• [Ultra Hi-Res self-extracting archive - Volume II]

Video/sound chips from MOS Technology and second source/clone vendors