APC series
The NEC APC, APC II and APC III were the international versions of models from the Japanese NEC  series.  The 8086-based N5200, developed by the Large Computer Systems division and released in 1981, was the first computer to use the NEC µPD7220 High-Performance Graphics Display Controller. 

The much better known PC-9800 series, released a year later by the Personal Computer Systems division, had a similar architecture to the original N5200 and used many of the same components. The most significant differences between the two were that the PC-9801 had slightly lower vertical screen resolution, graphics were standard instead of optional (still using a second µPD7220) and it used 5.25" floppy drives instead of 8".

The APC IV, despite sharing the series name, was an ordinary IBM PC/AT compatible and not compatible with the earlier APC models.

APC

The first APC was released in 1982 at $3,298 for a single-floppy monochrome system or $4,998 for a dual-floppy color system. It used a 16-bit NEC μDP 8086 CPU with 128K of RAM (expandable to 256K), 8K of ROM, and 4K of battery-backed CMOS ROM, a clock/calendar chip, parallel printer and RS-232 serial interfaces, and one or two built-in 8" floppy diskette drives supporting both single-sided single-density (243 KB) and double-sided double-density (1 MB) formats. (An external 10 MB hard disk drive was also available.)  The detachable keyboard had 86 keys (including the numeric keypad) and an additional 22 function keys.

Display 

A built-in 12" monochrome or 8-colour display was driven by an NEC µPD7220 display controller generating an 80 column by 25 line character display. (An additional line at the top of the screen displayed status information.) Each character was displayed in an 8×19 dot cell (giving 640×475 screen resolution) and could be one of 250 predefined 7×11 glyphs from ROM or 256 user-defined 8×16 glyphs from RAM. Each character cell also had an attribute byte indicating the colour (or, for monochrome screens, whether it was highlighted or not) and any mix of reverse video, blinking, over-bar, under-bar and blanked (not displayed).

The optional graphics board adds a second µPD7220 graphics controller with up to 512K memory displaying 640×494 graphics that overlay the text screen output. (This is higher than the resolution of the user-addressable text screen because graphics can overlay the status line as well.) The graphics controller allows panning the screen over the display memory, zooming, independent scrolling of different screen areas and other graphics functions. A light pen can be used for input.

Software 

Operating systems included CP/M-86 and MS-DOS.

APC III

The APC III (Advanced Personal Computer) was released by NEC in 1984. An update on the NEC APC II, which replaced the original NEC APC, all the NEC APC models utilized the Intel 8086 processor, unlike the IBM PC and clones.

The unit was physically smaller than an IBM-PC. The compact case included two 5" half-height disks (two floppies or one floppy and one hard disk), and space for standard options (hard disk controller, additional video memory). Special options (including additional system memory) required using expansion slots, of which four were available.

C-bus expansion cards (PCBs) could be inserted without removal of the exterior case, as was required for the IBM PC.

The entire computer could be disassembled to functional blocks (e.g.: expansion card cage, power supply, disk drive cage) with removal of a few easy access screws. Other components didn't even need a screwdriver, except for the outer case, by using robust plastic clips. The disk cage could be further disassembled if required. 

As with the IBM PC, the maximum usable memory was 640 KB (the address range of the Intel 8088 and 8086 is 1 MB). The APC came with 128 KB standard.

Specification

Hardware

Interfaces
RS-232 serial, 'Centronics' parallel and video interfaces were built onto the motherboard, whereas expansion cards were required for almost every function of an IBM PC except for the CPU, BIOS and built-in RAM.

Display
Maximum display capabilities were a text mode of 80×25 characters (with four planes) and/or graphics at 640×400 pixels (with two planes). Either text, graphics, or graphics with text overlay were software selectable. The base one bit-per-pixel was easily upgradeable to three bits per pixel (taking the graphics mode from monochrome to either eight colours or eight shades of grey). The computer was capable of running monochrome (or grey) through an NTSC TV monitor, although this was not recommended (text reduced to 40×20, graphics to 640×200). Monochrome (usually green) or color screens were usually included in the price. The APC III's 'on-board' video controller meant that upgrades (other than internally mounted video memory) could not be achieved, and the display was stuck at 640×400×3.

The NEC APC series supported a proprietary NEC APC character set and user-definable fonts in text mode.

Expansion bus
The expansion bus supported 16-bit-wide data and 20-bit-wide address capability. By comparison, the original IBM supported an 8-bit data bus with 20-bit address, which was later revised to 16 data bits and 24 address bits in the PC AT.

The motherboard was designed to allow easy addition of an 8087 math co-processor.

Disk drives
Most Australian units were shipped with 720 KB floppy disk drives (80 track, double density), although specifications imply the drives were only 360 KB (40 track, DD). 360 KB disks were readable and writeable by 'double-stepping' the 720 KB drives.

Users could also purchase a hard disk expansion option. This was initially limited to the 10 MB ST-506 hard disks. This capacity could be increased to 20 MB (but no higher) after upgrading to MS-DOS 3.1.

The hard disk controller was only configured to operate a single internal hard disk. An external hard disk expansion port was available, but compatible external hard disks were never produced.

Operating systems
Shipped standard with MS-DOS 2.11, other operating systems were available, such as the Unix derivative, PC-UX. Later, MS DOS 3.1 was released for the APC.

Compatibility
The APC III was not fully compatible with the IBM-PC, either on a hardware level (although some parts were compatible), or a software level (although again, some software was compatible). 

The earlier penetration of the market saw PC clones adopt the IBM PC architecture. In the export markets, NEC fell into line with the 16-bit IBM-AT architecture and did not pursue the APC-III architecture any further.

APC IV

The APC IV, released in 1986, was an IBM PC/AT clone that was not designed to be compatible with previous APC models.

See also 
NEC APC character set
NEC PC-9800 series

References

Further reading 
 "NEC APC-III Owner's Guide", NEC Corporation August 1994.

External links 
 The APC III at Old Computers Net
 NEC APC. Bryan Skinner checks out NEC's long overdue comeback in the big business micro field  Personal Computer News, September 29, 1983, pp. 34–41
 The APC-III at the On-line Computer Museum
 NEC APCIII; NEC's PC with style. Product review in Creative Computing, Volume 11 Number 02 (February 1985), pp. 60–64; article also available (minus photos) as a web page
 NEC APC III. MS-DOS Machine with a display that overcomes IBM PC incompatibility; review in InfoWorld, February 25, 1985, pp. 42–43
 The NEC APC III. A business computer with high-resolution color graphics Byte Magazine Volume 10 Number 03: Bargain Computing (March 1985), pp. 256–265
 IBM Compatibility for the NEC APC III. An operating-system patch and a few other alterations give the NEC APC III clone status., BYTE Vol 10-09: 10th Anniversary Issue, September 1985, pp. 171–179
 NEC APC III. Trappings of a Winner, Bits and Bytes (NZ), May 1985 pp. 13–16

NEC personal computers