MOS Technology VIC

The VIC (Video Interface Chip), specifically known as the MOS Technology 6560 (NTSC version) / 6561 (PAL version), is the integrated circuit chip responsible for generating video graphics and sound in the Commodore VIC-20 home computer. It was originally designed for applications such as low cost CRT terminals, biomedical monitors, control system displays and arcade or home video game consoles.

The chip was designed by Al Charpentier in 1977 but Commodore could not find a market for the chip. In 1979 MOS Technology began work on a video chip named "MOS Technology 6564" intended for the "TOI" computer and had also made some work on another chip, "MOS 6562" intended for a color version of the Commodore PET. Both of these chips failed due to memory timing constraints (both required very fast and thus expensive SRAM, making them unsuitable for mass production). Before finally starting to use the VIC in the VIC-20, chip designer Robert Yannes fed features from the 6562 (a better sound generator) and 6564 (more colors) back to the 6560, so before beginning mass production for the VIC-20 it had been thoroughly revised.

Its features include:
* 16 KB address space for screen, character and color memory (only 5 KB points to RAM on the VIC-20 without a hardware modification)
* 16 colors (the upper 8 can only be used in the global background and auxiliary colors)
* two selectable character sizes (8×8 or 8×16 bits; the pixel width is 1 bit for "hires" characters and 2 bits for "multicolor" characters)
* maximum video resolution depends on the television system (176 × 184 is the standard for the VIC-20 firmware, although at least 224 × 256 is possible on the PAL machine)
* 4 channel sound system (3 square wave + "white" noise + global volume setting)
* on-chip DMA
* two 8-bit A/D converters
* light pen support

The VIC was programmed by manipulating its 16 control registers, memory mapped to the range $9000–$900F in the VIC-20 address space. The on-chip A/D converters were used for dual paddle position readings by the VIC-20, which also used the VIC's lightpen facility. The VIC preceded the much more advanced VIC-II, used by the VIC-20's successors, the C64 and C128.

VIC IC list

*MOS Technology 6560 NTSC
*MOS Technology 6561E PAL Ceramic version, used in early VIC-20's
*MOS Technology 6561-101 PAL

References

*Bagnall, Brian (2005). "On The Edge: The Spectacular Rise and Fall of Commodore". Variant Press. ISBN 0-9738649-0-7.

ee also

* Video Display Controller
* List of home computers by video hardware

External links

* [http://www.geocities.com/rmelick/6561.txt VIC Chip info from Rick Melick's VIC-20 Tribute Page]
* [http://www.geocities.com/rmelick/6561d.txt More info, incl register usage]
* [http://www.zimmers.net/anonftp/pub/cbm/documents/chipdata/6560.zip MOS VIC datasheet (GIF format, zipped)]