【Toshiba】 TOSBAC-1150 System VI Sheet File System

This was Japan's first true floppy disk drive (FDD) based small business computer -- Marketed in 1974 by Toshiba. At the time, magnetic disk units had already begun to be used in small business computers, but their use was limited to high-end small business computers due to their high price, and magnetic cassette tapes were the main device used for low-end small business computers. Diskettes were originally introduced by IBM as a replacement for edge cards. (The name "diskette" was a trademark of IBM, but later people began to call this new media the "floppy disk" or simply "floppy".) Toshiba began to study the possibility of using these diskettes as an external memory device in low-end small business computers, but there were almost no examples of true use of a FDD as a file unit, so first they had to conduct tests to determine reliability. As a result of repetitive evaluation, it was confirmed that the disks could withstand 500,000 accesses, and Toshiba decided to use the drives, but originally they were used only for reading. Later, it was verified that write reliability was adequate, and the system became the pioneer of subsequent low-end small business computer design. According to documents at the time, the word "floppy disk" was not used. The media was called a "sheet file". The specifications of the sheet files used at the time were as follows:

Media size: 8-inch
Capacity/disk: 256 kilobyte
Data transfer speed: 250Kbps
Rotation speed: 360rpm

The TOSBAC-1150 System VI Sheet File System, which supported a FDD, was a model in the TOSBAC-1150 Series which was first marketed in the previous year (1973). The System I, II, III, IV and V were already available in this series. The System I and II were paper tape based systems, and the System III was a cassette magnetic tape based system. The System IV and V enabled online processing with an additional communication controller and network controller.

TOSBAC-1150 Series Arithmetic/Logic Control Unit
Logic element LSI, MSI, SSI (TTL element)
Memory unit Element MOS IC
Number of bits 8bit 1bit (parity)
Cycle time 800nsec/B
Capacity 1KB, 2KB, 4KB, 8KB, 12KB, 16KB
Arithmetic/logic control Instruction length 2B(16bit)
Number of instructions 65
Arithmetic system Decimal, binary parallel and fixed point
Address system Single address system
Address modification Direct or indirect indices (4 registers)
Control system Microprogram system
Interrupts 2 types
Controllable input/output devices Max. 16

TOSBAC-1150 System VI Sheet File System