Depending on the model of the machine (the processor is less important than other parts):
OpenBSD
NetBSD
FreeBSD
Linux
OpenVMS
It might be an issue if the machine doesn't have SRM, but instead AlphaBIOS/ARC firmware. But you can supposedly replace the ARM Firmware with SRM, so maybe it won't be an issue. And it's possible Linux doesn't have an issue with ARC, I don't know.