Based on what I found, I would conclude the following.
There are only 2 hardware revisions of the board:
501-505 are all the same original hardware rev, just different BIOS revs.
506-507 is the newer hardware rev, again with different versions of BIOS between the two versions.

I searched the intel.pcnalert.com website and
Here a little more information about revision 506.
(Other than what I highlighed in bold, I don't think the other changes are really that useful.)

1. Updating the BIOS to revision 2507.
2. Adding the option to use both Maxim parts and the existing Pericom
parts in PCIe x8/x8 switching circuit.
3. Adding an enhanced revision of the ADI voltage regulator controller.

Additional items for retail desktop boards:
a. China RoHS documentation enhancements.
b. Updated printed product guide.
c. Updated the driver CD.

http://intel.pcnalert.com/content/eo...N107244-00.pdf

If you conclude differently, please let me know.
Thanks.


Quote Originally Posted by screwtech02 View Post
I'm thinkin this is super secret "Intel" only info... Cause i have never seen it DISPLAYED ANYWHERE.....