From 1984, a third-party second processor for the BBC Micro, with a 68000 and running a Unix (System III):
Photo from this review in Acorn User.
There’s a Z80 in there too, to run CPN and to boot the (8MHz) 68000. And with a 20MB hard drive and 256k RAM or more, you won’t be surprised to hear it cost £3000 in basic configuration.
When the Acorn 16032 second processor comes out, ostensibly providing Xenix at around the £1000 mark, Unicorn will no longer be the cheapest [route to Unix].
As the hard drive was connected to the 8-bit host, I/O was not fast:
The power of Unix carries a cost, in terms of memory requirements and speed, that the Unicorn is barely capable of meeting.
And don’t hit the prominent Break key, as the machine takes 4 minutes to boot, and the filesystem might even be corrupted.
As an interesting note, the Torch second processors do use the Tube connector to the Beeb, but merely as a 2MHz peripheral bus: they use a 6522 to talk to their subsystem, not a Tube chip.
A note from the review about the future:
Now [Unix] is becoming available on microcomputers. In ten years’ time, the megabyte micros we all hope to have will almost certainly provide Unix or a descendant of it.
Here’s a brochure with some technical information:
More here, of course: