The MISOSYS Hard Drive Kit

written by Matthew Reed

The MISOSYS Hard Drive Kit

MISOSYS Hard Drive Kit advertisement from the Summer/Fall 1992 issue of The MISOSYS Quarterly

The MISOSYS Hard Drive Kit was a hard drive interface for the TRS‑80 Model III, Model 4, and Lobo MAX‑80. (There was no version for the TRS‑80 Model I.) It was announced in the Spring/Summer 1989 issue of The MISOSYS Quarterly and began shipping in September 1989. It came in in two configurations: 20 MB and 40 MB.

Although Roy Soltoff described the MISOSYS Hard Drive Kit as a “pre-assembled kit,” it came fully assembled, tested, and ready to connect to the TRS‑80. The only other item needed was the “host interface cable” which cost $20.00 extra originally but was later included in the package.

The complete unit was housed in a 5.5″ high, 7″ wide, and 15″ deep case, which had room for two half-height drives. The case contained a 60-watt power supply and fan. The shipping weight of the entire package was 20 pounds.

The MISOSYS Hard Drive Kit consisted of three parts:

  • A hard drive (a 20 MB Seagate ST225, 20 MB Kalok KL320, or a 40 MB Seagate ST251)
  • A hard drive controller (either the Adaptec 4000A or the Xebec S1410A)
  • A 3.6″ by 6.3″ host adapter (designed and manufactured by MISOSYS) to interface the controller to the TRS‑80

When it was introduced in 1989, the 20 MB package for the Model III and Model 4 cost $495.00 and the 40 MB package cost $645.00. The 20 MB package for the Lobo MAX‑80 cost $450.00 and the 40 MB package cost $600.00. (The reason the Lobo MAX‑80 version cost less was because the MAX‑80 already had an Adaptec 4000 hard drive controller built-in.)

Also available was a hardware real-time clock option (which cost $30.00) and a joystick option (which cost $20.00). The joystick option came with a Kraft Mazemaster joystick and was compatible with the Alpha Products joystick and the Big Five TRISSTICK. This meant that TRS‑80 joystick-compatible games would automatically work. The real-time clock was included in some later versions of the kit.


The MISOSYS Hard Drive Kit came with a 59-page manual and both Model III and Model 4 versions of the hard drive software. Some of the supplied programs1 included:

  • FSCSI4/CMD, a low-level formatter
  • MSCSIF4/CMD, a high-level formatter
  • HDCHECK4/CMD, a utility to test all sectors of the hard drive
  • MSCSI4/DCT, the hard disk driver
  • SDFORM, a “sub-disk partitioning utility” to create smaller logical partitions within a hardware partition2
  • ARCHIVE4/CMD, a utility to archive the contents of the hard drive to floppy disks
  • RESTORE4/CMD, a utility to restore archived files from floppy disks
  • MSCPARK4/CMD, a head parking utility
  • JSTICK4/FLT, a keyboard filter to allow the joystick to generate five key values
  • SETJS4/CMD, a utility to set those five key values
  • MCLOCK4/CMD, a utility to read and set the hardware real-time clock
  • MALARM4/CMD, a program to set the hardware real-time clock alarm

There were also patches to make LDOS and LS‑DOS automatically use the real-time clock.

Bundled software

For a time in late 1991, MISOSYS offered bundled software already installed on the hard drive. These bundles included:

  • “Model III Games Galore” for $40.00
  • “Model III Business Bonanza” for $50.00
  • “Model 4 Business Bonanza” for $50.00
  • “Model 4 Ultimate Utilities” for $50.00

Perhaps the most interesting bundle was the $50.00 “Programmer’s Powerpack” which contained:

  • MC C compiler
  • MRAS macro assembler
  • HartFORTH Forth compiler
  • DSMBLR Z80 disassembler
  • CON80Z, a utility to convert Intel 8080 source code to Zilog Z80 format
  • UNREL, a utility that “converts REL to ASM”
  • The Source, three-volume book set containing the complete source code of TRSDOS/LS‑DOS 63

Price reductions

In 1990, the prices for the MISOSYS Hard Drive Kit remained the same, but the host interface cable and the clock option were added to the packages for no extra cost.

In early 1991, the prices were reduced to $475.00 for the 20 MB version and $595.00 for the 40 MB version. In late 1991, the prices were further reduced to $450.00 for the 20 MB version and $575.00 for the 40 MB version.

The final price reduction was in 1992, when the prices were reduced to $395.00 for the 20 MB version and $495.00 for the 40 MB version (although the real-time clock was no longer included and only available as an option).

The MISOSYS Hard Drive Kit was one of the last products MISOSYS sold. As far as I know, it was still available for sale until MISOSYS closed down on March 1, 1994.

  1. The Model III versions of the programs had a 3 in the filename instead of a 4, for example HDCHECK3/CMD
  2. This was a customized version of the DiskDISK hard drive utility. 
  3. The Source three-volume set cost $297.00 when it was first published in 1982. 
Categories: Hardware

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