The author describes how Version 7 UNIX was ported to a Data General Eclipse Minicomputer. The Eclipse is similar to the PDP-11, on which UNIX was developed, in that it uses 16 bit logical addresses alongside memory management. On the other hand, the architecture of the Eclipse, in particular its memory management unit, is very different from that of the PDP-11. The main problem faced was in porting the UNIX kernel, which is too large to fit in the Eclipse’s 64K logical address space. The solution chosen was to dynamically remap the kernel; a large part of the paper describes how this was organized. Also described are a number of other PDP-11/Eclipse incompatabilities and the ways they were circumvented.

What is missing from the paper is any discussion of the performance of the ported UNIX, other than the statement that it is “quite adequate.” Even some crude comparisons with the original PDP-11 would have been welcome.

The project described would seem to have been overtaken by advances in hardware. It is difficult to see why anybody should want to port UNIX to a machine with such an unsuitable architecture as that of the Eclipse. There are inexpensive microprocessors available, like the Motorola 68000, which are capable of directly addressing several megabytes of memory.