DAI Personal Computer
Encyclopedia
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
from the Belgian
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
company Data Applications International. The DAI came to market in 1980. It provided many pioneering features such as high resolution color graphics, a maths co-processor, and a pre-compiling BASIC interpreter. But it never became a commercial success.
History
The computer was initially designed by DAI for the UKUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
subsidiary of Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
for use with the PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
televisions used in Britain. TI US did not want to build a PAL version of their TI-99/4A
Texas Instruments TI-99/4A
The Texas Instruments TI-99/4A was an early home computer, released in June 1981, originally at a price of USD $525. It was an enhanced version of the less-successful—and quite rare—TI-99/4 model, which was released in late 1979 at a price of $1,150...
home computer, although they subsequently authorized one after they saw the DAI .
The Dutch educational TV broadcast company Teleac wanted to use the DAI to teach computing, following the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
's program using the BBC Micro
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
. However, they chose the Exidy Sorcerer
Exidy Sorcerer
The Sorcerer was one of the early home computer systems, released in 1978 by the videogame company, Exidy. It was comparatively advanced when released, especially when compared to the contemporary more commercially-orientated Commodore PET and TRS-80, but due to a number of problems including a...
instead, because the DAI was not completely ready.
Main technical specifications
The DAI was based on an early 8-bit microprocessorMicroprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
, the Intel 8080 A
Intel 8080
The Intel 8080 was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It was an extended and enhanced variant of the earlier 8008 design, although without binary compatibility...
, (which is generally considered the first really usable microprocessor) and contained on a single printed circuit board all the needed circuitry, some 120 individual ICs. The futuristic-looking white enclosure also held a high quality keyboard, which was uncommon for the time. As a computer display
Computer display
A monitor or display is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure...
any TV
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
could be used, on which the DAI could display text and high resolution color pictures. It contained a memory controller that enabled it to use up to 48KB of DRAM
Dram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
. This memory was divided in three 16KB regions (memory banks), that could contain either 4K or 16K memory chips. By using memory map switching a total of 72kB of memory was addressable. The DAI also had five programmable interval 64µ - 16ms interval timers that could generate interrupts. The built-in interrupt handler chip could also handle two external interrupt inputs and the interrupts of two serial RS232 UARTS. The DAI featured a DAI/Indata DCE parallel I/O bus for parallel high speed I/O. The DAI also had 3 sound generators and 1 noise generator, and was capable of generating stereo sound.
Graphics capabilities with 48k RAM installed allowed up to 240 x 528 pixels in 4 out of 16 color palette in 4 successive blobs, leaving 16k programming space. The graphics modes were controlled by a device called Programmable Graphics Generator, implementing several techniques:
- decoupling physical scan lines from the 'logical' lines. The repeat count of physical scan lines could be 0 to 15 per line (Due to interlacing a physical scan was two pixels high),
- configurable horizontal resolution per line,
- using indexed colors,
- limit modifying the color palette to one color per line.
In 4 color mode, per logical line one foreground and one background color could be selected, so each line element or logical pixel could be represented by one bit.
In 16 color mode, the color palette was inherited from the previous line. only one of the four usable colors could be changed.
The special thing was, that this limitations were handled by Basic, so the user didn't notice his feet were tied together Basic allowed only the whole screen in one mode, but poking
PEEK and POKE
In computing, PEEK is a BASIC programming language extension used for reading the contents of a memory cell at a specified address. The corresponding command to set the contents of a memory cell is POKE.-Statement syntax:...
directly in memory allowed mixed resolution lines. The whole PGG was implemented with two PROMs
Programmable read-only memory
A programmable read-only memory or field programmable read-only memory or one-time programmable non-volatile memory is a form of digital memory where the setting of each bit is locked by a fuse or antifuse. Such PROMs are used to store programs permanently...
and standard TTL logic. The scheme predated the Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
HAM mode by half a decade.
The BASIC
BASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
interpreter was remarkably fast for the time because it pre-compiled to an internal byte-code, unlike the Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
BASIC interpreter which most other systems of the time used. This is a significantly more difficult trick than doing the same for C or other compiled languages, as the byte-code had to be re-expanded so it could be edited as is usual for BASIC. DAI variables could be up to 14 characters long. The internal byte code used pointers to a variable look up table at the bottom of the code, which made the code extremely compact, despite long variable names.
This technique was rare (only other known example is the ABC 80), and is remarkably similar to that now used for Java.
To enhance the mathematical abilities of BASIC, (and assembler programs) an AMD
Advanced Micro Devices
Advanced Micro Devices, Inc. or AMD is an American multinational semiconductor company based in Sunnyvale, California, that develops computer processors and related technologies for commercial and consumer markets...
AM9511 floating point co-processor
Floating point unit
A floating-point unit is a part of a computer system specially designed to carry out operations on floating point numbers. Typical operations are addition, subtraction, multiplication, division, and square root...
(compatible with the Intel 8231) could be added.
As a subject for a business management seminar, the development of the DAI PC is fascinating. The first working example was produced in less than 3 months, by 3 people, one of whom was taping up the circuit board layout. All 64K of assembler was the work of one man David Collier, and all the hardware design the work of another David, David Lockey.
The original decision to use the 8080A 1 MHz processor(already in use by DAI on other products ) was forced by the ridiculous timescale, which itself was dictated by a desire to show the machine to a TI USA board meeting. In the end only a trip on Concorde got the machine there on time. However the slow CPU dictated a huge amount of work on the pre-compiling BASIC, and the option for hardware-assisted floating point which might not have been required if the newer Z80 had been chosen. If a proper 16-bit CPU could have been applied the machine would have been a real contender, but would certainly have missed the TI and Teleac deadlines.
The decision to design the PC to use any old off-the shelf cassette tape recorder made the load and save speeds dauntingly slow.
The need to keep the end-user cost down dictated the need for extra complexity to output a TV signal capable of working with a domestic TV, though a dedicated monitor would have been simpler and given better results. Fascinatingly, when TI finally did put the 99/4 onto the European market a few months later, it was initially sold only in a pair with an American NTSC TV because it could not drive European PAL and SECAM ones.
Further technical details
- CPU: an Intel 8080A at 2 MHz
- Memory: a maximum of 48KB dynamic RAM, 24 KB ROM and 256 Bytes of static RAM (stack RAM)
- Keyboard: 56 Keys
- Video interface: a PALPALPAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
. NTSCNTSCNTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
or SECAMSECAMSECAM, also written SÉCAM , is an analog color television system first used in France....
compatible color-TV output signal- Text mode: 60 characters × 24 lines
- High resolution graphics modes: low - 65 x 88 pixels; medium - 130 x 176 pixels; high - 260 x 352 PixelPixelIn digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s - available colors: 4 or 16 colors (16 color mode was actually 4 color palette)
- Cassette interface: Audiocassette (600 BaudBaudIn telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
) - Alternative main storage systems:
- The "DAI Memocom Data Recorder" (which used Philips minicassetteMinicassetteThe Mini-Cassette, often written minicassette, is a tape cassette format introduced by Philips in 1967. It is used primarily in dictation machines and was also employed as a data storage for the Philips P2000 home computer...
s) - Two eight inch floppy disk drives (which enabled the use of CP/MCP/MCP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
).
- The "DAI Memocom Data Recorder" (which used Philips minicassette
- PeripheralPeripheralA peripheral is a device attached to a host computer, but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture....
s: a card rackComputer busIn computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
, the ("DAI Real World Card System"), could be connected through the DCE-Bus to the DAI. - Input-Ports: 2 PaddlesPaddle (game controller)A paddle is a game controller with a round wheel and one or more fire buttons, where the wheel is typically used to control movement of the player object along one axis of the video screen...
and two RS-232 serial input ports. - Output-Ports: 2 stereo audio outputs, and two RS-232 serial output ports.
- Sound generation: 3 stereo voices + 1 noise generator,
- System software:
- a machine code monitorMachine code monitorA machine code monitor is software built into or separately available for various computers, allowing the user to enter commands to view and change memory locations on the machine, with options to load and save memory contents from/to secondary storage.Machine code monitors became something of a...
with the following commands:- LOOK
- DISPLAY
- GO
- FILL
- SUBSTITUTE
- MOVE
- EXAMINE
- EXAMINE REGISTERS
- VECTOR EXAMINE
- VECTOR EXAMINE BYTES
- READ
- WRITE
- a built in DAI BASIC interpreter.
- a machine code monitor
- the system was also supported with a 8080-Assembler.
- miscellaneous: a true random number generator implemented in hardware.