[wtallis]

Xeon has implied ECC support for as long as Xeons have had integrated memory controllers, which is just a generation or two further back than the first Xeon E3 product line. Before that, ECC support was a function of the northbridge.

[binarycrusader]

Hmm, perhaps this is a quirk of ark.intel.com then; it shows that (as an example) that the Xeon X5690 supported ECC, but the Xeon L5638 did not.

The list on WikiPedia also seems to imply that not all models did historically, perhaps this reflects the northbridge change?