APC III

The APC III (Advanced Personal Computer) was released by NEC in 1984.[1] An update on the NEC APC II, which replaced the original NEC APC from the early 1980s, all the NEC APC models utilized the Intel 8086 processor with a 16-bit memory bus, unlike the IBM-PC and clones, which relied on the 8-bit bus of the Intel 8088 processor. It was advertised to business users.

Specification
Feature APC-III IBM-PC
Speed 8 MHz 4.77 MHz
Resolution 640×400 640×200
Storage (floppy) 720 KB (80 track, DD) 320 KB (40 track, DD)

Overview

The unit was physically smaller than an IBM-PC. The compact case included two 5​1⁄4" 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.

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).[2] 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[3] (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.[4]

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.

See also

References
  1. "日電、パソコンの対米輸出に本腰、ソフトは現地社から、TVなどで大規模宣伝も。" [NEC is now committed to breaking into the U.S. with their PC . Its software will be available from the U.S. subsidiary and the advert will be broadcast widely.]. 日本経済新聞 (The Nikkei) (in Japanese). 日本経済新聞社. 1984-07-09. p. 11. NEC has released the APC-3 in the United States. Its features are similar to the PC-9800 series.
  2. "APC-III System Reference Guide, Section 4 (Display Controllers)", NEC Information Systems March 1985
  3. "APC-III System Reference Guide, Section 1 (Hardware Overview)", NEC Information Systems March 1985
  4. "APC-III System Reference Guide, Section 2 (System Board) Figure 2.21 (hand-written notes)", NEC Information Systems March 1985

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