Why are these SGI boxes double-high?

It turns out all this SGI gear is coming from Boeing. That means the Onyx 2 Reality Monster is likely to have a nice multi-head configuration :-). Woo hoo! So my question is... why is this Onyx and Challenge pictured in a double-high cabinet? <http://www.dovebid.com/assets/display.asp?ItemID=cpt58902> <http://www.dovebid.com/assets/display.asp?ItemID=cpt58877> Usually when I see a Challenge or Onyx in a photo I see a cabinet that is half the height of these and that includes space for all the boards and drives. So what would you need the extra cabinet space for? More boards and drives or just more drives? -- "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/>