http://www.cisco.com/en/US/docs/unified_computing/ucs/interoperability/matrix/r_hcl_B_rel1.42.pdf
This document can be used for Hardware and Software Compat.
I think they are referring to the base level of ESX/ESXi 4.0 and 4.0 Update 1
If you look at the interoperability matrix it states in note 20
"56xx processor family require Patch04 or later"
This note goes away after the 4.0 U1 listing.
If you look at the VMWARE site HCL it shows the following versions supported with 56xx. From here if you type in Cisco for keyword and choose the Intel 56xx processor you will get output for all B-Series servers.
http://tools.cisco.com/squish/88a388