I don't know of anyone using big endian with Alchemy at this point.
There may be some and I'd like to hear from them.
The OSS tree is actually not that far out of date now. I have been
submitting patches and the basics work now (at least on my board).
I am currently working on the 36-bit support. The 36-bit support only
works for little endian currently afaics. I'm working to solve the endian
Check out the howto at http://www.linux-mips.org/. There are 3 of
us doing Alchemy work who hang out on the #mipslinux irc channel
on irc.openprojects.net you're welcome to join us.