If the problem is reproducible with SS-10, I'd definitely go with the
SS-10 ones, because SS-10 is a sun4m machine. Sun4c was never properly
supported in QEMU, and actually its support is completely removed from
the recent versions.
>My IPC has 2.4, I just verified.
I think it's worth saving it anyway. I don't expect it's support would
appear in QEMU (unless there was software which run on sun4c, but not
on sun4m. If such software existed I'd definitely try to resurrect
emulation of sun4c in QEMU), but it may work with some other
emulators, like TME.