I think so. Almost all documentation on the Tahoe has been lost in the mists of time (if ANYONE retains ANY hardcopies of ANY hardware documentation for the Tahoe, PLEASE let me know), but I recently managed to work out a bit about it from the instruction decoding/printing routines in the debuggers from 4.3 BSD Tahoe: https://gunkies.org/wiki/Power_6/32 and it seems to be fairly different from the Interdata: http://bitsavers.org/pdf/interdata/32bit/29-365R01_32BitRefMan_Jun74.pdf Also, 'CCI' is 'Computer Consoles Incorporated', not "Concurrent Computer Corp". Noel