Regarding the SE7520AF2, previous generations of the Intel Xeon processor are not supported. Some early revisions of the board did not correctly support the 2.80GHz 800MHz FSB processors. A link where you can the integration guide to determine if you have one of these early revision boards is http://www.intel.com/support/motherboards/server/sb/CS-021536.htm . For more information regarding the SE7520AF2 you may reference the link http://www.intel.com/support/motherboards/server/se7520af2/
A link with the information regarding the SE7320SP2 is http://www.intel.com/support/motherboards/server/se7320SP2/ . A .pdf file which shows the supported processors may be found at http://download.intel.com/support/motherboards/server/sb/se7320sp2_se7525gp2_tps_40.pdf In the document it does state that the Intel Xeon 533MHz processors running at 2.8GHz, 3.06GHz and 3.2GHz are not supported.
I hope this has been helpful.