rjek's right. I've an R140 and RISC iX was supplied on the hard drive. There's a RISC OS !RISCiX application that will boot into RISC iX, replacing RISC OS. Given that the 50-oddMB Rodime ST506 hard drive the machine shipped with was nearly completely filled with RISC iX, with a tiny RISC OS partition, and using squashed binaries at that, it was never shipped in ROM instead.
A 66MB hard drive? Given ST506 only went up to 56MB I guess that's SCSI.