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UNIX PC / PC 7300 / 3B1[1]
ManufacturerConvergent Technologies[2]
TypeProfessional Computer
Release dateMarch 26, 1985 (1985-03-26)[3]
Introductory priceUS$5,095 (equivalent to $14,400 in 2023) - US$7,290 (equivalent to $20,700 in 2023)[3][4]
Media5¼-inch floppy disks, optional QIC tapes
Operating systemAT&T UNIX v3.51[1] (Based on SVR2)
CPUMotorola 68010 with custom MMU clocked at 10 MHz
Memory512 KB to 4 MB RAM
Storage10 MB, Optional 20 MB, 40 MB,[2] and 67 MB hard drives[1]
Display12 inches (30 cm), 720 x 348
InputKeyboard, 3-button Mouse
ConnectivityRS-232 port, Parallel port, 3 phone jacks
Mass40 lb (18 kg)

The AT&T UNIX PC is a Unix desktop computer originally developed by Convergent Technologies[2] (later acquired by Unisys),[5][1] and marketed by AT&T Information Systems in the mid- to late-1980s. The system was codenamed "Safari 4"[6] and is also known as the PC 7300, and often dubbed the "3B1". Despite the latter name, the system had little in common with AT&T's line of 3B series computers. The system was tailored for use as a productivity tool in office environments and as an electronic communication center.[7]

Hardware configuration[edit]

Exterior of the AT&T 3B1
Motorola 68010 in an AT&T 7300 UNIX PC
  • 10 MHz Motorola 68010 (16-bit external bus, 32-bit internal) with custom, discrete MMU[2]
  • Internal MFM hard drive, originally 10 MB,[3] later models with up to 67 MB[1]
  • Internal 5-1/4" floppy drive[2]
  • At least 512 KB RAM on main board (1 MB or 2 MB were also options), expandable up to an additional 2 MB via expansion cards (4 MB max total)[2]
  • 32 KB VRAM
  • 16 KB ROM (up to 32 KB ROM supported using 2x 27128 EPROMs)
  • 2 KB SRAM (for MMU page table)
  • Monochrome green phosphor 12-inch (300 mm) monitor[2]
  • Internal 300/1200 bit/s modem[2]
  • RS-232 serial port[2]
  • Centronics parallel port[2]
  • 3 S4BUS expansion slots[2]
  • 3 phone jacks[2]

PC 7300[edit]

The initial PC 7300 model offered a modest 512 KB[2] of memory and a small, low performance 10 MB hard drive.[3] This model, although progressive in offering a Unix system for desktop office operation, was underpowered and produced considerable fan and drive bearing noise even when idling. The modern-looking "wedge" design by Mike Nuttall was innovative, and the machine gained notoriety appearing in numerous movies and TV shows as the token "computer".[8]

AT&T 3B/1[edit]

An enhanced model, "3B/1", was introduced in October 1985 starting at US$8,495 (equivalent to $24,100 in 2023).[9][1] The cover was redesigned to accommodate a full-height 67 MB hard drive.[1] This cover change added a 'hump' to the case, expanded onboard memory to 1 or 2 MB, as well as added a better power supply.[1]


Convergent Technologies offered an S/50 which was a re-badged PC 7300.[10]

Olivetti AT&T 3B1[edit]

Olivetti released the "Olivetti AT&T 3B1 Computer" in Europe.[11]

Operating system[edit]

Video of an AT&T PC 7300 booting
AT&T PC 7300 compiling and running a C program

The operating system is based on Unix System V Release 2,[2] with extensions from 4.1 and 4.2 BSD, System V Release 3 and Convergent Technologies.[1] The last release was 3.51.[1]

Windowing software (xt/layers) from SVR3 was provided to allow connection to a DMD 5620 graphics terminal.

Programming languages[edit]

Application software[edit]

  • Business Graphics (produces chart graphics from 20/20 spreadsheet data)
  • dBASE III (DBM)[3]
  • Informix (DBM)
  • Oracle (DBM)
  • Paint Power (drawing package)
  • Samna/AT&T Write Power 2 (word processor/spreadsheet)
  • Samna Plus (word processor/spreadsheet)[12]
  • SMART System (Office Suite)
  • Sound Presentations (presentation graphics)[13]

Spreadsheet software[edit]

Word processors[edit]



Expansion cards[edit]

The UNIX PC has three proprietary S4BUS slots for expansion cards:

  • DOS-73 8086 co-processor card running at 8 MHz, Hercules graphics-compatible, with 512 KB RAM, an RS-232 COM2 port and optional 8087 math co-processor. Mouse, floppy, modem (on COM1), and printer are shared in a DOS session. MS-DOS 3.1 was included. This board was designed and built for AT&T by Alloy Computer Products of Framingham, MA.
  • RAM could be added using 512 KB RAM or 2 MB RAM cards, up to a maximum of 4 MB (2 MB on the motherboard and 2 MB on expansion cards).
  • EIA/RAM combo cards contained extra RAM (512 KB, 1 MB, or 1.5 MB) and two RS-232 serial ports.
  • Dual EIA port card (same card as the EIA/RAM but without the RAM sockets)
  • StarLAN 1 Mbit/s (1BASE5) network over twisted-pair wire local area network typically used in star format
  • Ethernet 10 Mbit/s LAN card (AMD Lance-based) using AUI connector and Wollongong TCP/IP stack/drivers
  • AUDIX Voice Power (“Speech Processor”) card allowed for the capture and digital recording of voice conversations. This was an option of the "Integrated Solution" package for the AT&T System 25 PBX where the UNIX PC served as the "Master Controller".[17]
  • PC/PBX Connection Package 4 for AT&T PBX System 75 or System 85
  • Floppy Tape card provided interface for 23 MB MFM Tape Cartridge Drive (e.g. Cipher FloppyTape 525)
  • QIC-02 card for tape backup
  • Expansion chassis card was hard-wired to the externally-powered Expansion Unit with five additional S4BUS slots (manufactured by Alloy Computer Products)
  • Piiceon Model SR-2048 (2 MB) RAM expansion card

Public domain software[edit]

The STORE! was a public domain software repository provided by AT&T and accessible via dialup UUCP.[1][18]


The FreeBee emulator is available at FreeBee on GitHub.

Cancelled successor[edit]

Three prototypes of a follow-on "P6" model were alleged to have been built[19][1] with the specifications claimed to be:

See also[edit]


  1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac "3b1 FAQ". unixpc.org. Retrieved 1 August 2019.
  2. ^ a b c d e f g h i j k l m n Mayer, Alastair J. W. "System Review: The AT&T UNIX PC" (PDF). Byte. No. May 1986. pp. 254–262. Retrieved 2019-08-01.
  3. ^ a b c d e f g h i j k l m n Howitt, Doran (1984-04-08). "At Last, AT&T's 7300/Unix PC". Infoworld. p. 17. Retrieved 2019-08-01.
  4. ^ "AT&T Introduces Computer Gear Aimed at IBM-Led Office Market".
  5. ^ CBR Staff Writer (December 13, 1988). "UNISYS Corp Puts Ely in Charge of $2,000m UNIX Group". Tech Monitor. New Statesman Media Group Ltd. Retrieved November 29, 2021.
  6. ^ "NEW AT&T COMPUTER OFFICE GEAR". Chicago Tribune. March 27, 1985.
  7. ^ AT&T, Select Code 999-601-311IS, AT&T UNIX PC Owner's Manual (1986)
  8. ^ "AT&T PC 7300". Starring the Computer.
  9. ^ Petrosky, Mary (October 14, 1985). "6300 Plus Launched By AT&T". InfoWorld. Vol. 7, no. 41. p. 8.
  10. ^ "Vendors of Multiuser Microcomputer Products". Infoworld. 1986-10-13.
  11. ^ "Olivetti Technical Specifications". Olivetti.
  12. ^ "Samna Plans Unix-based Product Line". InfoWorld. June 16, 1986. p. 17.
  13. ^ a b c d e Satchell, Stephen (1985-09-23). "A Look at Software for AT&T's Unix PC". Infoworld. pp. 32–33. Retrieved 2019-07-30.
  14. ^ "Games".
  15. ^ "Comp.sources.3b1 Archive Volume 1".
  16. ^ "Miscellaneous Software".
  17. ^ AT&T System 25 Reference Manual. September 1989.
  18. ^ "The STORE".
  19. ^ "SVR3.5 + source code".

External links[edit]