SHARE | 
            |
 
                      
                   Scientific Data Systems 420 | 
              by Bill Degnan - 10/22/2020 15:51 | 
 
                
                 
                
                 
                
                 
                 
                
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                 
                
                 
                  ![]() The SDS 420 computer is a 6502 CPU computer with Persci model 277 dual 8" disk drives and proprietary operating system. Click image for larger view. 
More pictures I received the computer in pieces. The CPU board and RAM expansion board have a 1977 date on them but the actual machine was produced or last upgraded in 1979 (?). I worked with one of the engineers who built the computer, Bill Scheding, to re-assemble it. The Persci drives require repairs but overall everything looks good and should be fully restorable. I have a lot of notes and will post asap. Next - Rehab the drives and boot up the system. Document the memory map and archive the software. Reply  | 
            |
 
                      
                   Not Good | 
              by Bill Degnan - 04/19/2023 21:50 | 
 
                
                 
                
                 
                
                 
                 
                
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                
                  
                  
                  
                  
                  
                  
                  
                  
                  
                  
                 
                
                 
                  ![]() SDS 420 front 
Too many points of possible failure and no reference/schematic to reference. More pics Reply  | 
            |