"low cost time sharing system" was almost an oxymoron in the 60's and early 70's Both the cost of core, and for mass storage devices kept computer configurations capable of timesharing pretty expensive. TSS-8 was probably the first timesharing system for $50,000. As I recall, the final configuration of the TSS/8 system I used at the University of Wisconsin - Milwaukee was closer to $100K by the time we added the KL8/E's and RK05's. Early RSTS (originally called Edusystem-100) was somewhat less expensive, but the pre RSTS/E systems were pretty limited. There are a few other timesharing systems from the 60s for which software has been found that I'm aware of: Some bits of CTSS at Paul Pierce's web site Some of the MIT PDP-1 timesharing system The SDS-940 GENIE timesharing system The BCC-500 timesharing system. (I just received permission to release this) The Oregon State University OS-3 CDC 3300 timesharing system. CAL-TSS for the CDC 6400 may be on some 7 track tapes that were just given to Paul Pierce to read. There is also the software available for Hercules (TSS-360, for example)