We missed an article in OS/2 Ezine from last September but do think it's worth a read, given the long delay in Mikerosoft releasing Windows for AMD64.
The article says that OS/2 runs very well on AMD Opterons apart from a memory problem for DOSCALL1.
It also suggests that possibly 64-bit OS/2 plugins might become available or even a 64-bit OS/2 kernel.
We know that Big Blue had a version of OS/2 for the PowerPC platform but presume this is also sleeping in some corner of IBM, just like Windows for Alpha slumbers at Mikerosoft's HQ.
The article is here. ยต