I've worked on a machine with 9-bit bytes (and 81-bit instructions) and others with 6-bit ones - nether has a C compiler
The Nintendo64 had 9-bit RAM. But, C viewed it as 8 bit. The 9th bit was only there for the RSP (GPU).
I think the pdp-10 could have 9 bit bytes, depending on decisions you made in the compiler. I notice it's hard to Google information about this though. People say lots of confusing, conflicting things. When I google pdp-10 byte size it says a c++ compiler chose to represent char as 36 bits.
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