The systemboard design is/was only for UltraSPARC-IIIi modules.
The processor socket form factor is incompatible. The underlying design (comparable to the chipset functionality in an x86 box) is incompatible.
If you own a SB2500 and are hoping for some sort of upgrade path, it may be less expensive to go get an Ultra45 Workstation on eBay.
The following is a link to a diagram of the SB2500 systemboard.
It is from a web site that mirrors an ancient copy of Sun's "Sun System Handbook".
It's not an Oracle-hosted web site. I sometimes find it of use for basic information.
Cool! That will definitely come in handy. Also, I haven't got my 2500 yet so I'm wondering how well it does for stuff such as matlab and possibly hd video playback/encoding etc. Would you have any insight?
UltraSPARC-III era cpu modules compare very favorably with Intel processors of the same era.
So if you are familiar with Pentium-4 processors running at approximately 1.3GHz, then you'll be able to anticipate what your Sunblade 2500 and its US-III modules will do for you.
You can spend a bit of time spent with Google for further information.