I unearthed some old TU58 tapes that luckily was readable (after carefully replacing the tension band)
It resulted in two RT11 V4 images with two versions of the formatter program. One is bootable and the other not. http://storage.datormuseum.se/u/96935524/Datormusuem/Dilog/DQ604/sq604c.dsk http://storage.datormuseum.se/u/96935524/Datormusuem/Dilog/DQ604/sq604d.dsk I tried to run the formatter program in Simh: .run sq604C.sav TEST AND FORMAT DQ604 DISK SYSTEM (REV C.) DRIVE FORMATS AS RL01 UNIT (5.24 MB) SWITCH 3 CLOSED ENABLES BOOTSTRAP THERE ARE 17 PHYSICAL SECTORS PER TRACK (2) ALTERNATE CYLINDERS MAY BE ASSIGNED PER UNIT THE INTERLACE FACTORS ARE TWO OR THREE TO ONE DATA BUFFER ERROR USE PROCEED (P) TO REPEAT TEST HALT instruction, PC: 006312 (BR 6202) .RUN SQ604D TEST AND FORMAT DQ604 DISK SYSTEM (REV C.) DRIVE FORMATS AS RL02 UNIT (10.48 MB) SWITCH 3 CLOSED ENABLES BOOTSTRAP THERE ARE 17 PHYSICAL SECTORS PER TRACK (4) ALTERNATE CYLINDERS MAY BE ASSIGNED PER UNIT THE INTERLACE FACTORS ARE TWO OR THREE TO ONE DATA BUFFER ERROR USE PROCEED (P) TO REPEAT TEST HALT instruction, PC: 006312 (BR 6202) So it appears to be runnable. I also found the manual for the board and scanned it: http://storage.datormuseum.se/u/96935524/Datormusuem/Dilog/DQ604/DQ604.pdf Now the next step is to see if this can make the DQ604 board I have working with David Gessweins MFM emulator.