Page 16 of the Technical Product Specification guide;
3.1.1 Processor Support
"The Intel Server Board SE7505VB2 supports one or two processors in the 604-pin FCPGA package."
-> Socket 604,http://en.wikipedia.org/wiki/Socket_604
-> Intel XEON processors ONLY
"When two processors are installed, all Processors MUST be of identical revision, core voltage, and bus/core speed."
-> Means you really should use two IDENTICAL processors.
"When only one Processor is installed, it should be in the socket labeled CPU1, and the other socket must be empty."
That's the processor socket furthest away from the black AGP graphics expansion slot, and closest to the outside edge of the motherboard.
(Page 104, and 105)
ONLY supports Intel Xeon processors with a 400MHz, or 533MHz FSB.
Dual-Core Xeon's start at 667MHz, and wouldn't work anyway; due to different Core architecture, and Instruction Sets.
667MHz, 800MHz, 1066MHz, and 1333MHz, for dual core Xeon's,http://en.wikipedia.org/wiki/List_of_Intel_Xeon_microprocessors#Xeon_.28UP.2FDP.29.2C_Dual_Core_2
(Scroll down just a touch, to get the Wikipedia 'banner' out of the way, or click on it's X)
Scroll down the page, look at the charts. Starts with 800MHz FSB for Dual Core, then goes 667MHz, 800MHz, 1066MHz, and 1333MHz, Front Side Bus.
Use Dual Core processors?
Two Single-Core processors.
Product Guide for the Intel Server Board SE7505VB2,
The above is a direct link to the PDF file, motherboard manual.
If it doesn't work just by clicking on it, then copy it; and paste it in your browser address bar. Press the Enter key.
(This is a PDF file. The computer you are using now has Adobe Reader on it, which uses PDF files.
After you click on the above link, or press the Enter key; it may take up to 30 seconds before the first page comes up.
Didn't want you to wait a few seconds, and think nothing is happening)
For additional questions please post in a Comment.