This a daughterboard available for Sun UltraSPARC workstations that is basically a PC. It includes a CPU (AMD 233 or Celeron 733), RAM (from 64 MB to 1 GB), video card, and sound card. The Solaris software for accessing this card will load one or two disk images stored on the Unix filesystem. In addition, with the correct drivers, the loaded OS can access the Solaris filesystem with the permissions of the user running the software. Once booted, the OS is run in a X-Windows window sized to its own resolution and using its own colour maps.
A fresh disk image has Sun's OpenDOS and includes scripts for installing various versions of Windows from a CD (without boot disks). I've read that through trickery one can install Linux but it involves compiling a 2.4.x kernel on a seperate Linux box, etc.1
The first generation of SunPCi cards used the same NIC as Solaris but needed a different IP address2. The second generation has its own NIC built-in. Also, you may wish to install drivers called NIS-gina to allow Windows NT to authenticate users via NIS3.
1: ie: I haven't tried it (not having a pressing need for Linux with native Solaris).
2: Both can't use DHCP!
3: There's no way to get Windows to authenticate using /etc/passwd.