• Category Archives TRS-80
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  • Micro Computer Devices – Selectra-Print


    Source: 80-US – January 1979 

    Apparently, 1979 was literally pre-history as far as home printers were concerned. Here we have an ad for a “Selectra-Print” system by a company called Micro Computer Devices (mcd). The Selectra-Print was not a printer exactly, it was a Selectric II typewriter modified to interface with a computer and automatically type your documents. This ad appeared in the January 1979 issue of US-80 which was a TRS-80 publication. The TRS-80 (Model I as it would later be known) had been released in 1979 and its successor, the Model III, was not yet available.

    This “printer” was not specific to the TRS-80 but it was one of the computers it was available for. It only cost a mere $1925 which adjusted for inflation would be about $6900 today. The TRS-80 version was a little more expensive than the $1850 standard price, I suspect because of the interface. Though an RS-232 interface was an extra $195 so I’m not sure what you could hook it to with no extras. However, it is advertised as being compatible with a bunch of computers including the Apple II, Commodore PET, Heath H8, IMSAI (Matthew Broderick’s computer from Wargames), Cromenco, Alpha Microsystems, Space Byte, North Star Horizon, SWTP, Vector Graphic, Sol, Plymorphic, Digital Group, Ohio Scientific, Altair, Sorcerer, Xitran, Rex, KIM, EXORcisor, etc.

    I guess one benefit of such a setup is that getting “letter quality” printouts wouldn’t be a problem.

  • TRS-80 Model II

    State of Technology, 1982

    TRS-80 Model II Computer with 8-Inch Floppy Disk


    The TRS-80 Model II was not a successor to the original TRS-80 as the name might suggest (that privilege would go to the Model III). I don’t know why they named their computers in this manner but I can certainly imagine that it was potentially confusing to prospective customers.

    The Model II, unlike the Model I, was designed from the ground up to be a business oriented machine. It was introduced a couple of years after the Model I (but before the Model III so at least the sequencing was consistent) and in many regards is a much more high end machine that either the Model I or Model III which came a year later.

    It featured a faster processor (4.00 MHz Z-80A as opposed to the < 2 MHz Model I), an 8-inch 500k floppy (as opposed to a cassette or 5.25-inch 180k floppy if you were lucky), an 80-column screen (as opposed to the 64 columns screen of the Model I/III), and more memory (32-64K vs. 4-48K). It also had a number of ports built-in that were not included on the Model I/III without additional costly expansion (RS-232 and Parallel). One further advantage it had was that it could run CP/M out of the box without additional modification. The mainstream TRS-80 line would eventually get some of these features with the Model 4 and 4D. In general, the Model II, in addition to having more features, was a higher quality machine.

    However, the one big disadvantage of the Model II was that it was not compatible with the mainstream TRS-80 line. As a result, there was far less software available for it natively though there was plenty of CP/M software readily available. Price would have also been a factor, at least for the average person looking for a computer. It cost well over double the most expensive Model I/III starting at $3450.

    The Model II was followed up with the Model 12 (at least they moved the numbering away from the mainstream TRS-80 line) and later the Model 16 and 16B/Tandy 6000 which became the most popular Unix based computer in 1984.

  • TRS-80 Model 4 (1984)

    Detail from 1984 Advertisement for the TRS-80 Model 4 Computer


    Radio Shack released the TRS-80 Model 4 as a follow-up to the Model III three years later in 1983. It looked essentially the same as the Model III except that it was an off-white color instead of grey/silver. Internally, there were some fairly significant upgrades, including:

    • CPU: Z80A @ 4 MHz (compared to the ~2 MHz model III)
    • Display: 80×24 (compared to the 64 columns of the Model III)
    • Available 64KB model (Upgradeable to 128KB of RAM)
    • Full support for CP/M without modification

    It also included an expanded keyboard and TRSDOS 6. For this version of TRSDOS, Radio Shack contracted with the maker of LS-DOS/LDOS, a popular and generally more capable 3rd party DOS produced for the TRS-80 line. They continued to market LS-DOS separately but it and TRSDOS were now essentially the same. The Model 4 was also 100% compatible with the Model III whereas the III had some incompatibilities with the original TRS-80.

    The following configurations were available:

    • A diskless version with 16KB RAM (cassette only): $999
    • A single disk version (180K single sided, double density) with 64KB RAM: $1699
    • A dual disk version with 64KB RAM: $1999

    There was also an upgrade available for Model IIIs that essentially turned it into a Model 4. It included a new motherboard and keyboard and cost $799.

    The Model 4 was the last major revision the the TRS-80 line though there would be a somewhat enhanced Model 4D released in 1985 that would be sold through at least 1991.

    As I mentioned in a previous post, my high school still had TRS-80 Model IIs and 4s in 1989-1990 that were used for programming (BASIC) classes. I’m not sure how much longer they were there though I think they were being used at least one more year after that and possibly longer.