For those who have more memory than the direct-mapped DMA window can address (this is usually ">1G" or ">2G"). then you can now use all that memory. This is because Jason has implemented mbuf support in the SGMAP routines. Along with this, the SGMAPS routines have been made a bit more efficient.
A binary snapshot of NetBSD/alpha -current, including these changes, will be available shortly.
All the code to make this work has been committed to NetBSD-current, and testing so far has been on an AlphaServer 1200. This is the same systype as the AlphaServer 4100, so MP configurations of that should also work well.
Systems that should work in an MP configuration:
The AlphaServer 8200/8400 won't work yet. There are a couple fixes which will need to be done before the 8200 and 8400 will work in an MP configuration.
More information, including dmesg output from Jason's system, is available in his announcement in the tech-smp mail archive.
NetBSD 1.5 is the latest formal release of NetBSD, which includes many significant new features and enhancements. You can try NetBSD/alpha 1.5 running on an AlphaServer DS-10L and see if NetBSD supports your software, or if it's something you'd like on your own system.
Update: This has been pulled into the netbsd-1-5 branch, so it will be available in NetBSD 1.5.1.