The Microtek MT-32

written by Matthew Reed

By itself, the TRS-80 Model I was capable of only limited expansion. In order to add memory beyond 16K and support floppy disk drives, Radio Shack sold an external device they called an Expansion Interface.

The Expansion Interface could expand memory to 48K, add a parallel printer port, and add a disk controller for connecting floppy disk drives. But an Expansion Interface with 32K of memory cost $597.00, almost $100 more than a 4K Model I. What if a Model I owner didn’t want (or couldn’t afford) disk drives but still wanted to add memory and a printer port?

The MT-32 from Microtek, Inc.¹ of San Diego, California used a different approach from the Radio Shack Expansion Interface. The MT-32, introduced in mid-1980, offered only two features: the ability to add 32K of RAM (for a total of 48K) and a parallel printer port.

Configurations

The MT-32 was available in four configurations:

• the MT-32K, came as a kit without RAM² for $79.50
• the MT-32A, came fully assembled without RAM for $99.50
• the MT-32B, came fully assembled with 16K RAM for $159.50
• the MT-32C, came fully assembled with 32K RAM for $199.50

Those were substantial savings when compared to Radio Shack’s price for the Expansion Interface (at the time) of $299.00 without RAM and $597.00 with 32K RAM.

The MT-32 came in a grey aluminum case measuring 3" by 7" by 16 1/2". Like the Radio Shack Expansion Interface, the MT-32 was designed to sit underneath the Model I monitor. It attached to the Model I using a cable connected to the 40-pin expansion bus. The MT-32 manual estimated that installation should take only 60 seconds.

One unusual detail of the MT-32 was that it provided a socket on its case to plug in the Model I power cord. This meant that the Model I power switch always remained on and system power was controlled using the power switch on the front of the MT-32.

Unlike most other Expansion Interface alternatives, the MT-32 didn’t include an extender for the Model I 40-pin expansion bus. Any device that needed to connect to the Model I bus, such as the Exatron String Floppy or the MECA BETA-80, couldn’t be used at the same time as the MT-32.

Discontinuation

Microtek, and their division Microtek Peripherals, sold many products for the Apple II, Atari, TRS-80, and (later) the IBM PC. They were also well-known for their inexpensive and popular Bytewriter printers. However, problems with excessive returns of Bytewriter printers led Microtek to declare Chapter 11 bankruptcy in August 1982.

They appear to have stopped selling the MT-32 and their other TRS-80 products around that time. Microtek continued to sell Apple II and IBM PC products until at least 1985.

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1. Microtek Inc. of San Diego appears to have had no relationship to Microtek International, a well-known scanner manufacturer in the mid-1980’s that still exists today. ↩︎

2. The MT-32 models without RAM were fully socketed for 32K and could be expanded with standard (for the time) 4116 dynamic RAM chips. ↩︎