The problem though may be in the DX9 emulation layer, possibly even Winblows own x86 thunking in general. Not sure if those runtimes will work well if you exceed the expected address space limits of the older x86 environments. Not entirely up to speed on whether the x86 implementation OS limits are still enforced somehow even within the x64 OS either. There could be some wonkiness in there where you still run up against the 2GB (or tweaked 3GB) user space cap like we did in 32-bit.

Microsoft has been f-cking with programmers for as long as I can remember. So glad I ran away from networking when Vista launched. Such a shame *nix and OGL never got the momentum it deserved.