TRS-80 Model III

TRS80 MODEL IThe TRS-80 series were designed for both Business and Home entertainment. The Model III featured internal bays for 5.25 disk drives, disk drive controller for internal and additional drives, built in 12 inch monitor, 16K or 48K memory, and a range of peripherals such as external disk drives, modems, RS232 modules etc. Later models were shipped with RS232C module, internal drives, and 48K of Ram.

There were two versions of drives the single side single density 180Kb, and double side double density 360Kb. The Design was unique for those days; everything was molded under one case, and very heavy compared to other personal computers. It was also compatible with previous models, which helped the machine to sell well due to already available software. The Cassette tape was used to backup personal software. There was software to backup the TRSDOS OS on tape but it was not a success since it took a lot of time to backup the entire floppy on tape. The TRSDOS OS had many utilities such as CONVERT, to convert programs from Model I to Model III and TAPE to transfer tape or disk software.

TRS-80 Model III
US $699 base model
US $2495 w/ 32K, dual drives.
No serial no. Sticker was removed.
Z80 processor running at a frequency of 2.02752 MHz
14K Rom including Basic, and Ram depends from model. There were 3 versions the 16K, 32K or 48K Ram versions. In order to use TRSDOS the machine had to be a 48K version.
Very heavy grey plastic case, with monitor drives and keyboard in one case. The 12 inch monitor has a very good resolution with brightness and contrast under the keyboard. Full QWERTY standard 65 keys keyboard, with reset button located on top left corner, ESC key and a numeric keypad.
Two Modes: Text Mode 64×48 Matrix and Graphics Mode 128×1024 Matrix with 2 colours monochrome. Displayable characters include the standard 96 text-characters with upper and lowercase alphabet, 64 graphics characters, and 160 special TRS-80 characters.
Simple Beeper driven by CPU.
1 x Bus expansion and 1 x Cassette port. Other modules could be fitted to expand the system such as RS 232C, printer ports, and External Disk Drives.
Two Internal Power supply one for Motherboard and peripherals and the other to power up the internal and external drives. Power supply output voltages are as follows +12V, -12V +5V, and -5V.
Dimensions 465mm x 520mm x 300mm (W x L x H) Weight Approx 20Kg
Around 60,000 units Worldwide

The Club currently owns one TRS80 Model I complete with manuals and various other peripherals such as ram and Floppy Drive Interface. The machine is not boxed but aesthetically is clean and free from scratches.


Cassette Port

5 Pin Din 180
at the computer

Pin Name Dir Desc
1 REM IN Remote Control
2 GND N/A Ground
3 REM OUT Remote Control
4 AIN IN Audio In
5 AOUT OUT Audio Out