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This extremely rare computer is Portable PC (IBM compatible) conceived in the same plastic case as the Pied Piper, released by the same company in 1983. This computer incorporates a lot of features in a compact case, which was quite innovative at the time: built-in LCD display, printer, modem, phone and disk drives !

The STM PC is based on an Intel 80186 processor and two quadruple-density disk drives. The processor is faster than the one used in the IBM PC, and the disk drives are twice as capacious as the PC’s. It has a built-in modem, a thermal printer, and the first LCD screen on the market (in 1984) with a full 25 lines by 80 characters. A nice touch is a hands-free telephone with directory and dialing software, which you can use even as you compute. STM was promoting its Personal Computer as an office-in-a-box that fulfills all your needs; the STM PC certainly came closer to this ideal than any of the machines that were at the time briefcase-size.

STM’s design was quite creative. The STM PC is a single unit about the size and shape of a small attache case (20 inches wide, 11 inches deep, 4 inches high). On the right are two half-height floppy disk drives. On the left is a sloped LCD screen. The keyboard fits into a plastic shell that you flip upside down and snap over the screen for transporting. The built-in printer is apparent only as two thin slots, one in the back and one in the top of the computer, through which roll paper passes. When closed up, and with its roll of printer paper and its power cord removed, the STM PC is a clean, rectangular box. Packing it up is easy, although fitting the coiled keyboard cord back into its little compartment is as difficult as refolding a roadmap.

At the back of the machine are a multitude of connectors: two RS-232 serial ports, a telephone miniplug socket, a socket through which an acoustical coupler can be attached to the built-in modem, a parallel printer port, a standard video jack, a color monitor jack, a connector for an expansion chassis (any IBM chassis, apparently, will do, as will IBM-standard cards), and an SCSI (small computer systems interface) connector to which several makes of hard disk could be attached.

Under its hood the STM is tightly packed. It has a couple of small fans. The machine is not meant to be probed by the user, a reasonable design principle since it has no internal space for board expansions, except for a slot holding an extra 256K of memory. (Early versions of the STM PC could be upgraded only by replacing their 64K chips with 256K chips.). Expansion boards can be added in an expansion chassis that is connected through the I/O expansion socket on the back. The STM has no slot for an 80187 coprocessor.

The STM PC portable model sold for $3,449 in october 1984. A desktop model with only one serial port and without an LCD screen, modem, printer, or telephone did cost $2,499. Both models include STM’s version of MS-DOS, and NewWord, a word processing program that imitates the popular WordStar. BASIC is not included.


The 80 x 25 LCD screen, made by Epson, can display just about everything an IBM PC screen can, although only in regular and reverse video; it had no equivalent to the bright and dim characters available on most CRT screens at the time. The LCD will display standard IBM graphics as well as text (640 by 200 pixels), but because it is proportionately much wider and shorter than a standard screen, your pie charts will come out as egg charts. A knob labeled Contrast lets you adjust the screen for viewing angle, and a backlight makes the screen glow a light-blue color.

The screen’s display area is 3"1/4 by 9"1/4 inches — large enough for use from a normal working position at a standard desk. However, its smooth, glass front panel seems to find some glare to reflect no matter what angle you view it from. The LCD screen is more comfortable to read by using the backlight in a somewhat darkened room.

An external monitor can also be connected to the PC via a RGB connector or Composite plug.


The STM PC uses Canon quadruple-density disk drives, which, in some of early advertising, STM claimed have a capacity of 2 megabytes. In the fine print, the company acknowledged it was quoting an unformatted capacity. STM’s formatted, usable capacity is in fact 712K per disk.

The disks are “sort of’ IBM-compatible. The STM PC can read IBM disks, so you can copy data from IBM to STM disks. You can load programs into the STM from IBM disks. But the STM cannot write information onto IBM disks, nor can the PC read STM disks. So disk compatibility between the two machines is a one-way street, from IBM to STM. The only way to get information out of an STM PC and into an IBM PC is through a wired communications connection. Because this incompatibility causes it some problems in the marketplace, STM also sold a version with 360K disk capacity.


STM has equipped its PC with an 80186 processor, an advanced version of the 8088 used by the IBM PC. The advantages of the 80186 include greater speed, more circuits on the main chip (which means fewer are needed in the rest of the computer), and a true, full-fledged 16-bit address bus. The disadvantage is that the different chip makes true PC-compatibility more difficult to achieve.

Accompanying the fast processor is a standard 2S6KB of RAM, expandable to 512KB for $500 (in 1984). The 256KB is not quite as usable as 2S6KB on an IBM PC because 38KB is occupied by special STM device drivers and other housekeepers, leaving 218KB of usable memory.

STM has engineered a system that runs an impressive array of IBM software even though it uses a different processor. And besides standard computer features, STM has thrown in a number of interesting and useful extras. Unfortunately, none of them quite lives up to its promise.


A thermal printer is handy while away from home. It prints on a 4-inch-wide roll of that nasty, tacky paper that discolors in your files, but for a quick printout, you’d think it should be fine. However, the printer can only be driven by the DOS PRINT command or by the PrtSc key. You cannot use it as an ordinary printer driven in the normal way from a program. For a program such as WordStar, which lacks a proper print-to-disk feature, using the STM built-in printer is a real problem.

In principle, the DOS PRINT program should be able to run in the background; you should be able to load another program and use it while the printing is going on. In fact, STM’s DOS allows you to load the other program, but doing so brings printing to a halt; the printer resumes when you exit back to DOS.

Unfortunately, the printer is so slow that background printing is essential. A page-long file took nearly 5 minutes to print. STM could have made its thermal printer more useful by buffering it.

The printer normally prints a 40-character line. It can print 80-character material as well, but only sideways, in 24-line chunks. Happy gluing! Sideways printing completely freezes the computer and takes even longer than 40-character printing — more than 10 minutes for a one-page file and 3 minutes for a screen dump. STM could have made its thermal printer more useful by buffering it, allowing the printer to proceed in the background while the computer moved on.


The STM PC has a built 300/1200 baud modem as well as a built-in hand free phone ! You can make or answer a call any time while using the computer.

We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.
Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).


Iwas the guy who designed the graphics to control LCDand extenal monitor. There were no off the shelf component at the time. So Idesigned from scrutch! I was told by marketing team that IBM and Apple engineers showed strong interest at Comdex. Our life has changed since then.

Tuesday 11th July 2023
Satoshi (Japan)


TYPE  Professional Computer
YEAR  1984
KEYBOARD  full-size detachable low profile keyboard. 83 key with numeric keypad and 10 function keys
CPU  Intel 80186
RAM  256 KB (up to 512 KB)
TEXT MODES  Monitor: 25 lines x 80 / 132 characters
built-in LCD display: 16 lines x 80 characters
GRAPHIC MODES  Monitor: 320 x 200 (color graphics mode), 640 x 400 (monochrome graphics mode)
built-in LCD display: 512 x 128
SIZE / WEIGHT  515 x 275 x 100 cm / 8 Kg
I/O PORTS  1 x parallel port (Centronics compatible), 2 x serial RS232C ports, SCSI hard disk interface, IBM PC I/O bus expansion connector, RGB video output, Composite video output
BUILT IN MEDIA  2 x double sided, double density, 96 TPI disk drives. Capacity of each: 1 MB unformatted, 800 KB formatted

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Ready prompt
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