The project was started in 1979, and appeared in NEC's "Advanced Personal Computer" or "APC" in 1980. The NEC APC sported a 5 MHz Intel 8086 processor on a 16-bit bus, and came with a text-only display board using this chip. An optional graphics-only display board "merged" the text and graphics video through an XOR port in HW. The only OS on the original NEC APC was the UCSD p-System, but later on CPM/86 support was added. In 1981, an English language paper written in 1980 by Tetsuji Oguchi, Misao Higuchi, Takashi Uno, Michiori Kamaya and Munekazu Suzuki was published in the IEEE. Nippon Electric Company deployed the chip in other computers, such as the NEC PC-9801, and NEC's APC II and later APC III computers, and also released it to other manufacturer's in Japan, starting in 1982. The same year, the 7220 was revealed in North America by NEC Information Systems, the US arm of NEC. By 1983, it was used in other early computers, from NEC and other companies including Digital Equipment Corporation and Wang Laboratories. A few years after its 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, 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.
Variants
Variants included:
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.
A follow-on project produced the μPD72120 Advanced Graphics Display Controller which was faster and supported a 16-bit interface. It was named one of the "Top 100" products of 1987 by Electronics Design.
Internals
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.
