AT&T Unix PC

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3B1 / PC7300 / Unix PC
Atandt unix pc.jpg
AT&T Unix PC
Manufacturer Convergent Technologies
Type Professional Computer
Release date 1985 (1985)
Media 5¼-inch floppy disks, optional quarter-inch cartridge tapes
Operating system AT&T Unix v3.51
CPU Motorola MC68010 with custom Memory management unit clocked at 10Mhz
Memory 512KB to 4MB RAM
Storage Optional 10MB, 20MB, 40MB, and 67MB hard drives
Display 720x348 pixel resolution
Input Keyboard, 3-button Mouse

The 3B1 (also known as the PC7300, or Unix PC) was a Unix workstation computer originally developed by Convergent Technologies (later acquired by Unisys), and marketed by AT&T in the mid- to late-1980s. Despite the name, the 3B1 had little in common with AT&T's other 3B-series computers.

Hardware configuration[edit]

Exterior of the AT&T 3B1
  • 10 MHz Motorola MC68010 (16 bit external bus, 32 bit internal) with custom, discrete MMU
  • Internal MFM hard drive, originally 5 MB, later models with up to 67 MB
  • At least 512K RAM on main board, expandable via expansion cards
  • 3 expansion slots
  • Monochrome green phosphor 10-inch (250 mm) monitor
  • Internal 300/1200 bit/s modem


The initial PC7300 model offered a modest 512 KiB of memory and a small, low performance 5 MB hard drive. 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 was innovative, and in fact the machine gained notoriety appearing in many movies as the token "computer."[citation needed]

AT&T 3B1[edit]

A later enhanced model was renamed "3B1". The cover was redesigned to accommodate a full-height 67 MB hard drive. 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.

Operating system[edit]

Video of an AT&T PC7300 booting
AT&T PC7300 compiling and running a C program

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

Programming languages[edit]

Application software[edit]

Word processors[edit]



The Store[edit]

The Store is a public domain software repository which was available for all 3B1 users.[4]

Expansion Cards[edit]

  • DOS-73 8086 co-processor card running MS-DOS, which could be fitted with an 8087 math co-processor chip. This board was designed and built for AT&T by Alloy Computer Products of Framingham MA.
  • RAM card could be added using 1 or 2 MB RAM cards (up to a maximum of 4 MB)
  • EIA/RAM combo cards contained extra RAM and two RS-232 serial ports.
  • Dual EIA port card
  • StarLAN 1Mbit/s LAN card
  • Ethernet 10 Mbit/s LAN card
  • VoicePower card allowed for the capture and digital recording of voice conversations.
  • Tape drive card provided interface for 23 MB MFM Tape Cartridge Drive.
  • Expansion chassis card was hard-wired to Expansion Chassis (with five added slots)


See also[edit]

External links[edit]