I've been trying to get various distros onto a Sunblade 150 over the last few weeks. There's a couple of things I've found that might help you:
1) Upgrade your OBP: You'll need an OS on the machine to do this (I used Solaris 10). Then you just grab the firmware, put it into the root directory and run this command from the ok prompt:
ok boot disk /<directory>/<file name>
in my case this was:
ok boot disk /flash/flash-update-Sunblade100-Sunblade150-latest
This should take care of the memory issues that you're having and may also help with the hardware detection.
Please note that if your hard disk has existing BSD or Linux partitions, Solaris may not be able to format the drive. I had to zero mine after FreeBSD locked it down.
2) Pass the ide=nodma argument to the SILO boot prompt
Sunblade 100'sand 150's seem to crash if you don't pass the ide=nodma argument to them. I tried a Gentoo install and it recommended using this option. Ubuntu server needs it too as it'll crash regularly otherwise.
Depending on what install you want to run (press Tab at the boot prompt to see the options) just append ide=nodma afterwards.
I used: Linux ide=nodma and it worked flawlessly.
You'll also need to add the 'append' string to your /boot/silo.conf
image=/vmlinuz
label=Linux
append="ide=nodma"
initrd=/initrd.img
Hope this helps,
Mark