I have a similar story; hopefully, somebody can give me some pointers on what I did wrong. Apologies for the long post--I'd rather be too detailed than waste anybody's time with suggesting things I've already done.
I have a recently-acquired Octane, with Xbow 1.3, Cherokee power supply, and IRIX 6.5.22 (and the corresponding PROM patch). The system came with SE graphics (which left me underwhelmed), so I Googled a bit, was led to this and other useful pages (including the installation guide mentioned by recondas), checked to make sure I met the requirements, found a V6 for sale, ordered it, and put it in. I stopped the boot at "Starting Up The System", went into Command Monitor, and saw GRAPHICS: ODYSSEY. Great! I booted IRIX 6.5.22 across the network from my Indigo (note: using 10base to serve your boot images is probably not the way to go), "open"ed the other three parts of 6.5.22 and every 6.5 CD I could think of, did "keep *", "install fresh", "conflicts" (no conflicts) and "go". Some time (and surprisingly, only about 3 CDs) later, it claimed to be done. I proceeded to "quit", restarted, and got to the wonders of:
"The system is coming up." And nothing further.
I left it that way for about half an hour in case it was doing something clever. No luck. Just to double-check that everything seemed correct, I booted into Install System Software across the network again, opened up everything it had asked for before, checked to make sure it saw the Odyssey graphics, did "keep *" and "install fresh", and "list"ed what files it wanted to install. It didn't want to install any, presumably because it thought they were already correct for the V6. This is the same problem I had when I upgraded my Indigo from Entry to Elan graphics, but I sidestepped that problem by upgrading to 6.5. This time, I'd rather not wipe the disk and reinstall, since I know I shouldn't have to and that there has to be something I'm just missing.
So, what am I doing wrong here? Would somebody who has done this successfully tell me if there's an extra step I wasn't aware of? Is there a way to see exactly what's happening during the boot process, rather than just "The system is coming up"? Alternatively, is there a way to completely reinstall the system without losing what's in /etc (other than tarring up /etc, saving it elsewhere, and untarring once I've rebuilt the system)? I'm pretty new to IRIX, so maybe these are the kinds of things that you "just know" from using it for a while.
Thanks for any help!