According to Richard Miller, "The First Unix Port" The first port began in 1976, at Wollongong, on an Interdata 7/32, 192k-core/2x5Mb disk drives.
In April 28, 1977, Unix version 6 was booting. When Bell Labs was contacted:
In fact there was a surprise on both sides: a team at Bell Labs was in the midst of doing their own port of UNIX to an Interdata 8/32 (a slightly more powerful 32-bit mini-computer). They had begun work at the beginning of 1977 in anticipation of the delivery of their machine in April and had a kernel working by June less than two months after the Wollongong kernel first ran on the bare 7/32.
The Interdata 7/32 and 8/32 were the first 32-bit machines to both run Unix version 6, which had the Interdata 8/32 port becoming the basis for UNIX 7th Edition.
Oddly enough, real information about this machine is near nonexistent, short of the SIMH simulator.
The Interdata 7/32 and 8/32 were Plug Compatible Mainframes/Minis of the System 360, differing both in character sets, architecture and of course machine code.