Update (10/17/06): I have created a static page with more detail for this issue since the post was generating quite a few hits.
Just got Ubuntu 6.06 running on a Sun Blade 150. Besides some RAM related weirdness – I had to remove one of the sticks of RAM to get it to boot and install – it went pretty smoothly. In fact it worked better than the Solaris 10 installation I had tried a couple of days ago. In the end I gave up on Solaris, it just wasn’t worth the hassle, though I will say that I did eventually get it into a semi-working state on the Desktop – it just took too long to get it there.
The Ubuntu server install booted without an issue. I then installed gnome, kde and the X font server – that was when things went wrong. The X Server (Xorg) would start but my monitor (a Dell 1905FP) would tell me that it couldn’t display that video mode. Despite trying every resolution and bit depth I could think of, this behavior persisted. It was then that I came across a post on the Ubuntu forums, it was for a Sun Blade 100 but the PGX64 card (which is ATI Rage based) was the same. The post contained the crucial information needed to remedy the problem, a line had to be added to the Device section of the xorg.conf config:
Option “ReferenceClock” “29.500MHz”
Once that had been added, the X Server came up and displayed without a hitch. Given how hard it was to find the solution, I figured I’d add my entry to try to boost the Google entries 
Every day I get more and more impressed with Ubuntu. It still has some way to go in terms of Enterprise tools, but for every day use it is starting to come into its own, and that is from someone with an RHCE
Technorati Tags: Sun Blade 150, Ubuntu, Linux, xorg, Sun
Thanks for posting this. It is one of the vital components of what I need for my ubuntu install on my sb 150. Any other issues since?
None at all – the box has been running just fine 24/7, no crashes, no other problems
How did you install x11 on sunblade150
can I get some guidance
Hi Adam
How did you install X11 on this box, I have been trying to compile and install , Can you put some lines here .
Hi other Adam – you did not leave an e-mail address, so I can only hope you check back here for a response. I installed X.org using Ubuntu’s apt-get package manager, and this page is about getting that to work correctly. I did not compile X or install in any other way. I no longer have the Sunblade 150 as I have changed jobs and offices and left it behind – sorry I can’t be more help – good luck!
Adam