ThinkSecret has what they claim are photos of the machine being shipped by Apple for Apple Developer Connection members; the Apple Development Platform ADP2,1. The machine’s case is similar to the G5, but the cooling fans inside are arranged differently, and in place of the standard G5 processor it has 3.6GHz Pentium 4 processors, 2MB of L2 cache, an 800MHz bus, and 1GB of RAM (no mention of whether it’s a single or dual processor machine.)
Apparently it’s possible to install & run Windows XP on the same machine, but it’s unable to make use of the entire screen. They also say that the OS X for Intel installer disk won’t work on Dell hardware. Too bad.