TSS-8

TSS-8 is a discontinued little time-sharing operating system co-written by Don Witcraft and John Everett at Digital Equipment Corporation in 1967. The operating system ran on the 12-bit PDP-8 computer and was released in 1968.

Authorship

TSS/8 was designed at Carnegie-Mellon University with graduate student Adrian van de Goor, in reaction to the cost, performance, reliability, and complexity of IBM's TSS/360 (for their Model 67). ^[2]

Don Witcraft wrote the TSS-8 scheduler, command decoder and UUO (Unimplemented User Operations) handler. John Everett wrote the disk handler, file system, TTY (teletypewriter) handler and 680-I service routine for TSS-8.

Roger Pyle and John Everett wrote the PDP-8 Disk Monitor System, and John Everett adapted PAL-III to make PAL-D for DMS. Bob Bowering, author of MACRO for the PDP-6 and PDP-10, wrote an expanded version, PAL-X, for TSS-8.^[3]

Architecture

This timesharing system:

was based on a protection architecture proposed by Adrian Van Der Goor, a grad student of Gordon Bell's at Carnegie-Mellon. It requires a minimum of 12K words of memory and a swapping device; on a 24K word machine, it could give good support for 17 users. ^[4]

Each user gets a virtual 4K PDP-8; many of the utilities users ran on these virtual machines were only slightly modified versions of utilities from the Disk Monitor System or paper-tape environments. Internally, TSS-8 consists of RMON, the resident monitor, DMON, the disk monitor (file system), and KMON, the keyboard monitor (command shell). BASIC was well supported, while restricted (4K) versions of FORTRAN D and Algol were available.^[5]

Historical notes

• TSS/8 sold about 100 copies

• Operating costs were about 1/20th of TSS/360. TSS/8 was also designed to be more cost-effective than the PDP-10 "for jobs with low computational requirements (like editing)." ^{[6] [7]}

• The RSTS-11 operating system is a descendant of TSS-8. ^[8]

References