SGI Indigo2 graphics options

Amongst other things, I picked up a SGI Indigo2 system yesterday. It turned out that it had the original packaging, and that it's an Impact 10000 machine. For graphics however it has a four-board set; does anyone know what this might be? Wikipedia talks about a three-board set for the Maximum Impact, and fewer cards for lesser options, but I've not seen mention anywhere of a machine using four (unless they're just not counting the analog output board as part of the three?) I'm not sure what it has for RAM; all of the sockets are filled. Someone had scribbled 32MB and 1GB of disk on the box, but it has 2 x 4GB drives fitted, so that's not necessarily correct. I need to clean the dust out before I try powering up, but does anyone know what a minimum config would be? Can I power up with no disks and framebuffer, and expect to get a serial console? I'd like to not stress the PSU (or risk the framebuffer cards) initially if possible - the previous owner said they never ran it, although it was supposedly working when they got it.