【Fujitsu】 USAC 820 , FACOM Bm

This was an ultra-small computer developed and manufactured by the USAC Electronic Industrial Co. The USAC 820 was announced by Uchida Yoko in September 1975 as the successor of USAC 720 Series, and the FACOM Bm was announced by Fujitsu in December 1975 as a lower computer of the FACOM V0Series (FACOM V0/V0S). Both computers were developed for comparatively small-scale enterprises whose main work was billing. In May 1977, 3 types were added, with shape designed to suit the type of printer used primarily for billing, and these formed the FACOM Bm Series and USAC 820 Series. These Series had the following features:

(1) They employed a standard floppy disk based system for the first time in the industry, thereby enabling data compatibility with upper models and different models.
(2) They were the first ultra-small computers to incorporate OS concepts.
(3) Operation was simple, and did not require a dedicated operator. (One-touch program startup using a program selection key, direct interaction with the computer using a display unit and journal printer etc.)
(4) Outstanding entry performance, and easy form design.
(5) Structure and design enabling installation in an ordinary office (The main unit was a desk-type locker, and expansion peripherals were installed in a rack.)
(6) They required no special construction of air-conditioning or power supply equipment (standardized at AC100V).
(7) They could be connected with the same peripheral devices as the FACOM V Series of small machines.

Many other enhanced models were announced later, but here we give the specifications of typical models from the early period.

(Note) The above specifications are from the time of announcement, and may have been changed due to later improvement.

Main Specifications of Typical Models in the FACOM Bm Series and USAC 820 Series
Model name FACOM Bm
USAC 820
FACOM Bm D type, USAC 820V FACOM Bm P type, USAC 820C FACOM Bm W type, USAC 820L
Announcement date FACOM Bm:
December 1975
USAC 820:
September 1975
USAC 820V/C/L: Announcement date is unknown. Completion date was December 1976 for the USAC 820V/C, and July 1977 for the USAC 820L.
Processor Microprogram control system, variable length word system, variable length instructions (2, 4, 6 bytes)
Operations: Binary, decimal, arithmetic, logic, conditions, edit
Main memory unit Memory element 4Kbit MOS-LSI memory
Capacity 20-2KB 32,40,48KB 24,32,40,48KB 32,40,48KB
Printer unit Printing system 7x9dot 7x9dot font 9x9dot
Print speed 120char/s 120char/s Average
Characters per line: 136char
/line (pica)
/line (pica)
/line (pica)
Built-in floppy disk unit Memory capacity
(8inch, single-sided)
Memory capacity
(8inch, single-sided),
Number of connected I/O units 6 (of which one was a communication line)
Other Early models of the FACOM Bm and USAC 820 Series were primarily for billing.
First standard floppy disk office computer
Standard model equipped with 640char display and dot printer Mass-market model with 15 numeric character display and font type library High-end model with 640char display and dot printer with a wide platen and two paper feed mechanisms