I'm sorry if this has been done before, but I could find no indication this was the case in the unix archive itself or in any of the months I checked in the mailing list. I have figured out what the first 50176 bytes of s1-bits are. It is an "INIT Tape" as described in Dennis_v1 Boot Procedures(VII) and Dennis_v3 bproc.8. It is apparently contemporary with s2 [all of the files on it /etc/getty /bin/ls and so on match up exactly with their counterparts on s2], and this would seem to make s2 the "/bin-/etc-/lib tape" described in bproc.8. Also - is there any other known copy of the "bos" bootloader? I'm partway through hand-disassembling the one on the tape. Anyone know how to get SIMH to send ^J for return? Anyway - with the KE-11A enabled you need to use "d system sr" to set the switch register [which must be set to 1 to cold boot, 73700 to come up in single user mode, and any random value other than the special ones 0 57500 10 20 40 1 2 to come up normally] The RF disk is not even large enough to contain the whole s2 tape, and while even v1 supported mountable filesystems, there is no mkfs or mount on the tapes.