DAI Personal Computer

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A DAI Personal Computer

The DAI personal computer is a rare and very early Home computer from the Belgian company Data Applications International that came to market in 1980. Initially designed by DAI for Texas Instruments UK, because TI US did not want to build a PAL version of their TI-99/4A home computer, (a situation that was later fixed when the bosses at TI US saw the DAI) it was (for its time) a very capable system with many features (such as high resolution color graphics, a mathematical co-processor, and a pre-compiling BASIC interpreter) that other systems acquired only much later. But, perhaps because it was too expensive and too fraught with problems and commercial bad luck, it never became a big success.

For example the Dutch educational TV broadcast company Teleac wanted to use the DAI to teach computing (similar to the BBC which choose the Acorn system that became the BBC computer), but at the last moment they chose the Exidy Sorcerer instead, because the DAI was not completely ready.

[edit] Main technical specifications

The DAI was based on a very early 8 Bit microprocessor, the Intel 8080 A, (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 any TV 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. This memory was divided in three 16KB regions (memory banks), that could contain either 4K or 16K memory chips. The DAI also had two programmable 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 BASIC interpreter was remarkably fast for the time because it pre-compiled to an internal byte-code, unlike the Microsoft 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.

This technique, which may be its first or only use in a BASIC interpreter, is remarkably similar to that now used for Java.

To enhance the mathematical abilities of BASIC, (and assembler programs) an AMD AM9511 floating point co-processor (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 under 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 Lockey. The original decision to use the 8080A (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.

[edit] Further technical details

CPU: an Intel 8080A at 2 MHz
Memory: a maximum of 48KB dynamic RAM, 24 KB ROM and 262 Bytes of static RAM
Keyboard: 56 Keys
Video interface: a PAL. NTSC or SECAM 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 Pixels
- available colors: 4 or 16 colors
Cassette interface: Audiocassette (600 Baud)
Alternative main storage systems:
- The "DAI Memocom Data Recorder" (which used Philips minicassettes)
- Two eight inch floppy disk drives (which enabled the use of CP/M).
Peripherals: a card rack, the ("DAI Real World Card System"), could be connected through the DCE-Bus to the DAI.
Input-Ports: 2 Paddles 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 monitor 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.
the system was also supported with a 8080-Assembler.
miscellaneous: a true random number generator implemented in hardware.