Biggest Onyx 2 rack configuration?

It seems that these Onyx 2 rack systems are pretty available. If I wanted to max out the system configuration, what's the theoretical max? I didn't even know they could gang 4 racks like the one I have. As I understand it, they subdivide a rack into "bricks" and then components (disk drives, graphics cards, etc.) plug into the brick. I believe the bricks are identified by a single letter code. Does anyone know of a reference for this sort of SGI stuff? I know SGI has manuals online, but it helps to know the specific manual to use as a starting point. The racks have an integrated power supply, so maybe they identify the amount of equipment per rack based on power consumption? -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>