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SGI O2 Prom modification

Subject: SGI O2 Prom modification
From: Glenn Barry <>
Date: Wed, 08 Sep 2004 14:04:50 +1000
Original-recipient: rfc822;
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.2) Gecko/20040803
Hi There,

I have two questions related to MIPS which someone may be able to help with. Sorry for the long post.

Firstly I don't know if you've heard about the upgrading of the RM5200 300MHz CPU modules in SGI O2's with RM7000C 600MHz chips.

You can read about it at

My question is about the possibility of someone helping out with modifying the O2's PROM to recognise the RM7900 CPU from PMC-Sierra.

Currently the RM7000C running at 600Mhz is a working modification. The RM7900 runs at up to 900Mhz and would breathe new life into the little O2's.

Details from a post on as to what needs to be done:

This guy was the one who has pioneered all of the CPU upgrades currently going on with SGI machines.

"For the O2, when you start the computer the CPU board reads the data from the boot-mode PROM chip (the Xilinx chip) into specific registers on the CPU chip and does a Power On Self Test (POST). If the POST passes, the ip32PROM then reads that data from the specific CPU chip registers and checks that the CPU module is returning data values the ip32PROM recognizes and passes those data values on to IRIX for the system. The problem is that the data is in different registers and has different values for the RM7900 series of chips than the RM7000 series of chips. The RM7000 chips and the RM5270 chips use the same data registers so the ip32PROM sees the RM7000 chips just fine, not so with the RM7900 chips. When ip32PROM does not see a data value it recognizes (for whatever reason), it halts the system at that point.
So at least three things need to be done to get this project back on track:
1.) a way needs to be found to tell the ip32PROM the correct registers to look in for the data on the RM7900 CPU chip 2.) new values need to be added to the ip32PROM's list of possibe data values for a couple of items 3.) the setup for the L2 cache in the ip32PROM needs to be changed as the RM7900 chips start the cache memory at a different memory location than the RM7000 chips If there is someone out there who understands the ip32PROM and how to modify the bin file, I will help them any way I can but the software part of this is beyond my understanding."

If anyone can help out with this, or know someone who can help, it would be much apreciated.


Not having played with Linux on my O2, I don't know the details, but are you able to run dual monitors with a second video card in the PCI slot?

If so does anyone think it would be possible to port a video card driver to Irix to be able run a second screen. Unfortunately the dualhead monitor adaptor isn't really an option as they are very difficult to find and expensive.



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