So the X2200M2 has an upgraded firmware that updates both the BIOS and the SP. Updating is a good thing, as there are a number of known problems with old version (open relay, amongst others).
For those updating, it's important to be aware of a few issues that you might run into.
When I tried this, I essentially lost all serial access to both the BIOS and the running instance of Solaris.
If you're running something older than the tools and drivers CD 1.3, then go to the 1.3 version first, and do the newer versions in a separate step. If you don't, you'll get a CMOS checksum error and will need to clear it. I found a physical power-cycle worked.
You might have to go into the BIOS and reset to optimized defaults.
Once you've updated to the current version, then you might have to go into the BIOS (under Advanced/Remote Access) and change the serial port from COM1 to COM2. Doh!
They default baud rate has changed back to 9600. You know all the customizations (including building a modified boot image on your jumpstart server) we've had to do to set the baud rate to 115200? Don't do those bits, they now cause more harm than good. (The other customizations are still necessary, it's just the baud rate.)
So after that I do get both BIOS access and can see Solaris booting up. I don't see grub coming up as it boots, though.