You can connect it to a serial terminal or USB to serial on your laptop - at 9600/8/n/e and boot without keyboard or video connected. You can hit ESC and in the PROM menu that appears you can enter the Command Monitor and do a 'hinv' command to print out what is in there.
System Maintenance Menu
1) Start System
2) Install System Software
3) Run Diagnostics
4) Recover System
5) Enter Command Monitor
Option? 5
Command Monitor. Type "exit" to return to the menu.
>> hinv -v
IP27 Node Board, Module 1, Slot n1
ASIC HUB Rev 6, 100 MHz, (nasid 0)
Processor A: 350 MHz R12000, Rev 3.5, 4M 233MHz secondary cache, (cpu 0)
R10000FPC Rev 0
Processor B: 350 MHz R12000, Rev 3.5, 4M 233MHz secondary cache, (cpu 1)
R10000FPC Rev 0
Memory on board, 4096 MBytes (Standard)
Bank 0, 512 MBytes (Standard) <-- (Software Bank 0)
Bank 1, 512 MBytes (Standard)
Bank 2, 512 MBytes (Standard)
Bank 3, 512 MBytes (Standard)
Bank 4, 512 MBytes (Standard)
...
like that.