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Tandy 600

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Tandy 600
Tandy 600 front view (Service Manual figure 1.1)
The Tandy 600 with its display closed, from Tandy's service manual (Tandy copyright)
Specifications
ManufacturerCustom manufactured for Radio Shack, a division of Tandy Corporation
TypeBattery-powered portable computer
ReleasedShown at Comdex/Fall 1985 (November 1985)
Intro priceUS$1,599
CPUMSM80C88, 3.07 MHz
Memory32 KB static RAM, expandable to 224 KB with 96 KB RAM cards
StorageBuilt-in 3.5-inch floppy disk drive (360 KB per the owner's manual)
DisplayLCD, 480 x 128 pixels, 80 characters by 16 lines
SoundPiezo buzzer
ROM160 KB in five 256 Kbit mask ROMs; the Multiplan ROM can be exchanged for the BASIC ROM
Ports / interfaceRS-232C (DB-25), Centronics printer (26-pin), telephone jack for the built-in 300 bit/s modem, 34-pin floppy connector
PowerRechargeable nickel-cadmium battery pack; 8 V DC adapter
DimensionsAbout 11½ x 12½ x 2½ in
WeightAbout 9½ lb
OS / FirmwareMicrosoft Works system manager in ROM
PredecessorTandy 200
Model no.26-3901

The Tandy 600 is a battery-powered portable computer sold by Radio Shack under catalogue number 26-3901, with a built-in 3.5-inch floppy disk drive, an 80-column by 16-line LCD and a 300 bit/s modem.[1] It runs an MSM80C88 processor, a low-power CMOS version of the 8088, at 3.07 MHz.[2][3] The 600 is not an IBM PC compatible: its applications run under a ROM-based operating system manager called Microsoft Works, and it does not run MS-DOS software.[2]

History

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80 Micro reported that Tandy showed the new Tandy 600 laptop alongside the Tandy 1000 and 3000 at Comdex/Fall 1985 in Las Vegas in November 1985.[4] The owner's manual carries a 1985 copyright from Tandy and Microsoft.[5] By March 1986 Radio Shack was advertising it at $1,599.[1]

80 Micro's review in the same issue called the 600 "the best combination yet of a functional, full-featured laptop" among Tandy's portables, but the reviewer could not "wholeheartedly recommend" it. The review praised the bundled software and criticised the 32K base memory, the proprietary operating system, the hard-to-read screen and the weight: 9½ lb, or 11 lb with the external power supply.[2]

Specifications

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Tandy 600 from Tandy's service manual
Item Detail
CPU MSM80C88, 3.07 MHz
RAM 32K bytes standard, 224K bytes maximum, 64 Kbit static RAMs; all RAM held by a backup battery while the power is off
ROM 160K bytes in 256 Kbit mask ROMs
Display 480 x 128 pixels, 230 x 61 mm, HD61830 controller with two 64 Kbit static RAMs; 80 characters by 16 lines in a 6 x 8 matrix
Keyboard 72 keys: 56 capacitive and 16 mechanical
Floppy drive 3.5-inch, 80 tracks at 135 tpi, MFM, 300 rpm, 500K bytes unformatted; WD2797 controller and µPD8257 DMA controller, powered down after 5 seconds without access
Modem 300 bit/s FSK, pulse and tone dialling, auto-answer; ring detection can switch the computer on
RS-232C 110 to 19,200 baud, configured as DTE
Clock HD146818 with alarm; an alarm can switch the computer on
Printer Centronics
Backup battery 51FT-P, 3.6 V 50 mAh, on the main board, charged from the main battery; keeps all RAM and the clock
Auto power off After 10 minutes without a key press

Source: the service manual.[3] The owner's manual and Radio Shack's advertisement give the diskette capacity as 360K, and 80 Micro describes the drive as single-sided.[6][1][2]

Optional equipment

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The owner's manual lists the BASIC ROM package (26-3904), 96K RAM upgrade kits (26-3910), a direct-connect modem cable (26-1410), a printer cable (26-1409), an acoustic coupler (26-3805), a null modem adapter (26-1496), DB-25 cables (26-4403 or 26-1408) and blank micro diskettes (26-0415).[6] 80 Micro gives the price of each 96K RAM board as $399.[2]

Hardware

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Tandy 600 main PCB OPMP silk-screen side (Service Manual section 9.1.1)
Silk-screen side of the OPMP main board from the service manual, with the five ROM sockets at the bottom, the RAM card connectors CN1 to CN3 in the middle and the backup battery BAT1 on the right.

Boards

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Tandy's service manual names four boards: OPMP, the main PCB; OPKK, the keyboard PCB; OPLF, the LCD controller; and OPRM, the RAM card.[7] The optional RAM card plugs into connector CN1 or CN2 on the main board, and the optional ROM chip fits under a cover at the rear of the case.[8] The parts list gives five 256K mask ROMs, HN613256P parts suffixed PS66, PS67, PS68, PS98 and PS99, and an IC chip carrier; the main board has five ROM sockets, ICN1 to ICN5.[9][10] The owner's manual describes the Plan ROM chip, which holds Multiplan, as interchangeable with the BASIC ROM chip, and both sit in a Molex carrier.[11] 80 Micro notes that BASIC can also be copied to disk, so that it and all the built-in applications can be used together.[2]

Power

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The computer runs from a rechargeable nickel-cadmium battery pack or an 8 V DC adapter, and the batteries recharge from the adapter.[6] The adapter socket is 5.5 mm, centre negative.[12] A DC/DC converter on the main board, a transistor driving pulse transformer TLA1 at 30 to 40 kHz, produces the +5 V, +12 V and −12 V rails; relay RL3 switches on the floppy drive's supplies only when the drive is accessed.[13] The owner's manual gives about 11 hours of use per charge with no input/output activity, 8 hours with 1 hour of printer, RS-232C or disk use and 6 hours with 1½ hours, and a full charge, with the computer switched off and the adapter connected, as about 14 hours.[14]

A small nickel-cadmium cell on the main board (BAT1) keeps the RAM and the clock alive while the computer is off. The Memory Power switch on the underside disconnects it; the owner's manual says to turn it off only for long storage or when a cold start does not work, and that doing so erases all data in RAM.[3][11][15]

Disk drive

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The drive is built in on the right-hand side and connects to the main board through a 34-way flat cable and a 4-way power lead.[16] The 600 came with a utilities diskette holding FORMAT, DISKCOPY, PRINTER.DVR, INSTALL and DBCALLS.LIB; FORMAT needs about 6.4K of free RAM to run.[17] Owners who no longer have that diskette load the utilities through the serial port.[18][19]

Documentation

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  • Tandy 600 Service Manual: Tandy's service manual, with disassembly, adjustments, troubleshooting flowcharts, parts lists and schematics
  • The owner's manual, the BASIC reference manual (26-3904) and the programmer's reference and BIOS specification are held at the Internet Archive.[5][20]
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References

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  1. ↑ 1.0 1.1 1.2 Radio Shack advertisement, "Meet the disk-based Tandy 600", 80 Micro, March 1986, inside front cover, scan at the Internet Archive (retrieved 2026-10-22). Catalogue number 26-3901, price $1,599, 32K RAM expandable to 224K, 3½-inch drive storing 360K, five resident applications, BASIC ROM 26-3904 at $129.95.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Bradford N. Dixon, "Tandy's Model 600: You Can Take It with You", 80 Micro, March 1986, pp. 27-28, scan at the Internet Archive (retrieved 2026-10-22).
  3. ↑ 3.0 3.1 3.2 Tandy Corporation, Tandy 600 Portable Computer Service Manual, catalogue no. 26-3901, hosted as File:Tandy 600 Service Manual (26-3901).pdf. Section 1, "Hardware Specifications" (PDF pages 17-20).
  4. ↑ Bradford N. Dixon, "Pulse Train: There's No Business Like Show Business", 80 Micro, March 1986, scan at the Internet Archive (retrieved 2026-10-22). Comdex/Fall 1985, Las Vegas, November; the Tandy 3000 and the new Tandy 600 laptop on the Tandy stand.
  5. ↑ 5.0 5.1 Tandy Corporation and Microsoft Corporation, Model 600 Owner's Manual, 1985, scan at the Internet Archive (retrieved 2026-10-22).
  6. ↑ 6.0 6.1 6.2 Model 600 Owner's Manual, "Introduction" (PDF page 13: RAM expansion, 360K diskettes, 8-volt adapter, nickel-cadmium batteries, optional equipment) and "The Equipment", p. 4 (PDF page 14: weight about 9½ lb, dimensions about 11½ x 12½ x 2½ in).
  7. ↑ Tandy 600 Service Manual (26-3901), preface (PDF page 5).
  8. ↑ Tandy 600 Service Manual (26-3901), Appendix D, "Installation of Optional RAM and ROM" (PDF pages 345-346).
  9. ↑ Tandy 600 Service Manual (26-3901), parts list, "Mechanical and Assembly Parts" (PDF page 201).
  10. ↑ Tandy 600 Service Manual (26-3901), section 9.1.1, main PCB silk-screen print side (PDF page 225).
  11. ↑ 11.0 11.1 Model 600 Owner's Manual, "The Equipment", Figure 4 (bottom view), items 13 to 16, p. 7 (PDF page 17).
  12. ↑ Tandy 600 Service Manual (26-3901), section 2, "Connectors, Switches and Controls" (PDF pages 23-24).
  13. ↑ Tandy 600 Service Manual (26-3901), section 5.13, "Power Supply Control and DC/DC Converter" (PDF pages 136-140).
  14. ↑ Model 600 Owner's Manual, "The Batteries", p. 19 (PDF page 29).
  15. ↑ Tandy 600 Service Manual (26-3901), section 5.12.1, real-time clock overview (PDF page 132): the battery backup is not active when the RAM backup switch is off.
  16. ↑ Tandy 600 Service Manual (26-3901), section 3.1, "Units and Boards" (PDF pages 27-34).
  17. ↑ Model 600 Owner's Manual, "The Disk Drive" (PDF page 26).
  18. ↑ "Model 600", Tandy Tech wiki, last edited 2 August 2026 (retrieved 2026-10-22). Utility Disk contents, main and memory batteries, RAM, option ROMs, cold and warm start.
  19. ↑ "Tandy 600 Battery", Vintage Computer Federation Forums, February 2019 (retrieved 2026-10-22). Running a 600 from a 7.5 V adapter, the Utility Disk, the memory backup cell.
  20. ↑ Tandy 600 Handheld BASIC Reference Manual (26-3904) and Tandy 600 26-3901 Programmers Reference and BIOS Specification, Internet Archive items (retrieved 2026-10-22).


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