The problem is that the PDP-10 is really unsuited to running C. It doesn't use 8-bit bytes and doesn't have a native "byte" datatype, just words and halfwords. There are byte instructions, but you have to construct a "byte pointer" to use them, which is a control word describing bytes of arbitrary size. The PDP-10 also has no single dedicated stack pointer, any AC except for the program counter can be used as a stack pointer, to its own independent stack if you want.
Isn't stack direction an ABI convention rather than language or processor limit? I mean if you are trying to run existing PDP-10 binaries (I don't know of any that are publicly available), sure. But just to get to the point that you are running bash and serving and HTML Hello World from Apache, it shouldn't be an issue.
> 8-bit bytes
Doesn't the C standard just specify the minimum range of datatypes, and the max? Don't know if you can tell the size of actual bit without triggering UBI. (obviously not a C programmer)
The standard specifies that you must have an independently addressable unit of storage that corresponds to the basic character set. The PDP-10 does not have this.
Oh, there is/was a C compiler for the -10 (KCC), but it wouldn't support the modern dialects that the *BSD kernels are written in. Just having the language isn't enough, you have to be able to support the build chain of a modern kernel.
