ABC 80
 | |
| Type | Home computer |
|---|---|
| Release date | 1978 |
| Operating system | 16 KB ROM + 16 KB ROM for BASIC[1] |
| CPU | Zilog Z80 @ 3 MHz |
| Memory | 16 - 32 KB RAM |
| Display | 12 inch monochrome monitor[1] |
| Graphics | Text mode 40×24 monochrome Teletext, 78×72 block graphics[2] |
| Sound | 1-channel Texas Instruments SN76477[2] |
| Connectivity | Tape recorder, relay, display/sound/power, 2×32 pin CPU bus (4680), RS-232 |
The ABC 80 (Advanced BASIC Computer 80) was a home computer engineered by the Swedish corporation Dataindustrier AB (DIAB) and manufactured by Luxor in Motala, Sweden in the late 1970s (first model August 1978) and early 1980s. It was based on the Zilog Z80 running at 3 MHz and had 16 KB RAM, expandable to 32 KB, and 16 KB ROM containing a fast semi-compiling BASIC interpreter.
ABC 80 normally used a dedicated (included) tape recorder for program and data storage, but could also be expanded to handle disk drives (and many other peripherals). Some sound effects could be produced by a Texas Instruments SN76477 sound chip which was connected to an 8-bit output port, but there was no way to control the chip's features in any detail, so sound was limited to 96 fixed sounds. The monitor was a black and white TV set modified for the purpose (an obvious choice since Luxor also made TVs). The computer had excellent I/O response times, something that was discovered when trying to upgrade to personal computers. The solution was to use a microcontroller that communicated with a PC. The main unit had a reset button as well.
ABC 80 was also manufactured on license as BRG ABC80 by Budapesti Rádiótechnikai Gyár in Hungary. It used the same keyboard, but the case was metal instead of plastic.
Popularity
The ABC 80 was a huge hit in Sweden, and grasped a majority share of the rising personal computer market thanks to its office software in Swedish. Although the ABC 80 fans would defend the ABC 80 by referring to its good BASIC and usable extension bus, it couldn't defend the home market against the gaming computers with color graphics and better sound that arrived in the early 80s like the Commodore 64, even though a new cheaper version was released that could use an ordinary TV instead of the dedicated video-monitor.
Luxor held on to its office market for a couple of years longer with the ABC 800 series, which had a more extensive BASIC, more memory and a 512×240 'high-resolution' graphics mode, but otherwise similar performance. In 1985 Luxor also tried to compete in the office market against the IBM PC with its ill-fated ABC 1600 and ABC 9000 series UNIX computers, but failed.
See also: Compis.
Performance
In order to see how the ABC 80 would compare to other contemporary personal computers, in 1982, the Swedish magazine Mikrodatorn performed a "benchmark" test using eight short BASIC programs (referred to as BM1~BM8) defined by the American Kilobaud Magazine and routinely used by the British magazine Personal Computer World for testing new machines. The result was that ABC 80's semi-compiling BASIC interpreter turned out to be faster than most other BASICs used in popular machines, especially when integer variables are used, the results for some well known computers were as follows (times in seconds, lower is better):
| Computer | CPU | [MHz] | BM1 | BM2 | BM3 | BM4 | BM5 | BM6 | BM7 | BM8 |
|---|---|---|---|---|---|---|---|---|---|---|
| ABC 80 Integer | Z80 | 3 | 0.3 | 1.1 | 3.5 | 3.5 | 3.6 | 5.8 | 9.3 | 6.5 |
| ABC 80 Floating point | 1.0 | 2.1 | 11.0 | 11.0 | 12.5 | 17.5 | 24.0 | 13.0 | ||
| IBM PC | 8088 | 4.77 | 1.5 | 5.2 | 12.1 | 12.6 | 13.6 | 23.5 | 37.4 | 3.5 |
| Apple III | S6502 | 2 | 1.7 | 7.2 | 13.5 | 14.5 | 16.0 | 27.0 | 42.5 | 7.5 |
| VIC-20 | 6502 | 0.98 | 1.4 | 8.3 | 15.5 | 17.1 | 18.3 | 27.2 | 42.7 | 9.9 |
| ZX81 in "fast mode" | Z80 | 3.25 | 4.5 | 6.9 | 16.4 | 15.8 | 18.6 | 49.7 | 68.5 | 22.9 |
As seen from the table, the ABC 80 were up to 4.7 times as fast as the IBM PC using integers and up to 2.5 times as fast using floating point calculations. However, due to a sub-optimal exponentiation algorithm, the ABC 80 was slow on BM8 (which was fixed in the ABC 800). Compared to the cheap Sinclair ZX81, the ABC 80 was actually 15 times as fast on the simple loop of BM1 (with the ZX81 running in fast mode, i.e. without a continuous TV-picture).
Sound
- Sine, noise, square wave. And mixing these.[3]
- Quick decay, sine overlay, high or low tone, pulse tone control, on and off.
Books on ABC 80
For the technically interested, the circuitry in the ABC 80 is described in detail in the book Mikrodatorns ABC (The microcomputer ABC), by Gunnar Markesjö. It starts off with a course in digital electronics and microcomputer principles (assuming some general knowledge in electronics) and then presents a large number of block diagrams and partial circuit schematics, covering most of the computer, along with detailed explanations of how it works and why certain solutions were chosen.
See also
References
- ↑ 1.0 1.1 "Greentac Blog: July 2008". 090502 greentacblog.com
- ↑ 2.0 2.1 "mess:drivers:abc80:abc80 [MESS DevWiki]". 090502 mess.toseciso.org
- ↑ ABC80 manual page 36