The High-Performance Graphics Display Controller 7220 (commonly µPD7220 or NEC 7220) is a video interface controller capable of drawing lines, circles, arcs, and character graphics to a bit-mapped display. It was developed by NEC and used in NEC's APC III computers, the optional graphics module for the DEC Rainbow, the Tulip System-1, and the Epson QX-10.
The µPD7220 was one of the first implementations of a graphics display controller as a single Large Scale Integration (LSI) integrated circuit chip, enabling the design of low-cost, high-performance video graphics cards such as those from Number Nine Visual Technology. It became one of the best known of what became known as graphics processing units in the 1980s.
The 7220 was announced by NEC Information Systems, the US arm of the Nippon Electric Company (now NEC) in 1982. The project was started in 1979, and a paper was published in 1981. By 1983, it was used in early computers from NEC itself, and others from Digital Equipment Corporation and Wang Laboratories. A year after introduction, one journalist said "The 7220 GDC chip is a component that even some of NEC's competitors have found too good to pass up." When the Apple Lisa was announced in 1983, the press raised questions on why the popular 7220 was not used. Bruce Daniels pointed out that the Lisa primarily used raster graphics (known as bitmap graphics at the time), which could be implemented with less expensive hardware support. Instead, graphics primitives were written in software. Development manager Wayne Rosing added that although the team knew about the 7220, it was not quite available when the design began. There were also restrictions on when the display memory could be accessed: only during certain times in the vertical refresh cycle.
- Intel licensed the design and called it the 82720 graphics display controller. Announced in 1982, it was the first of what would become a long line of Intel graphics processing units.
- East Germany (the German Democratic Republic) produced a replica designated U82720, used with the U880 replica of the Zilog Z80.
- The faster complementary metal–oxide–semiconductor (CMOS) variant was given the designation µPD72020.
A follow-on project produced the µPD72120 Advanced Graphics Display Controller (AGDC) which was faster and supported a 16-bit interface. It was named one of the "Top 100" products of 1987 by Electronics Design.
Two I/O channels are used, addressing A0 and A1. Reading A0 retrieves the 7220 status. Reading A1 fetches the first byte from the internal queue. Writing to the 7220 uses both registers; A1 for writing the command, A0 for writing the parameters to the queue. The parts had an 8-bit data path. Parts were available with clocks running from 4 MHz to 5.5 MHz, which was considered relatively high-performance for the time.
- Guido Dampf (Translated May 5, 2010). "Graphics with the NEC 7220: Direct access with Turbo Pascal". Retrieved July 27, 2013.
- F.Robert A. Hopgood, Roger J. Hubbold, David A. Duce, ed. (1986). Advances in Computer Graphics II. Springer. p. 169. ISBN 9783540169109. "Perhaps the best known one is the NEC 7220."
- Tetsuji Oguchi, Misao Higuchi, Takashi Uno, Michiori Kamaya and Munekazu Suzuki (February 1981). "A Single-chip Graphic Display Controller". International Solid State Circuit Conference (IEEE): 170–171. doi:10.1109/ISSCC.1981.1156160.
- David Needle (March 21, 1983). "NEC's 7220 GDC chip allows high-resolution color graphics". Info World. pp. 31–34. Retrieved July 29, 2013.
- Wayne Rosing, Bruce Daniels, and Larry Tesler (February 1983). "An Interview with Wayne Rosing, Bruce Daniels, and Larry Tesler: A behind-the-scenes look at the development of Apple’s Lisa". Byte Magazine. pp. 90–114. Retrieved July 29, 2013.
- Hal W. Hardenberg (April 1983). "An Introduction to the 7220". DTACK Grounded (Digital Acoustics). pp. 8–9. Retrieved July 31, 2013.
- Changon Tsay (January 1, 1986). "A graphics system design based on the INTEL 82720 graphics display controller". Dissertation (University of Texas at El Paso).
- "Intel Corporation Annual Report". Intel. 1982. Retrieved July 27, 2013.
- 82720 GDC Application Manual. Intel, reprinted from NEC. July 2983. Retrieved July 27, 2013.
- "Integrierte Schaltkreise: Schaltkreis U82720". Robotron Technik. Retrieved July 27, 2013. (in German)
- "Graphics Display Controller simplifies programming". Electronics Design. May 14, 1987. p. 106.
- "µPD72220/GDC, µPD72220-1/µPD72220-2 Graphics Display Controller". The data sheet. NEC. April 7, 1983. Retrieved July 29, 2013.