There have been rumors floating around that Xbox One dev kits may have specs and features different from those of the actual retail units. According to Microsoft's Director of Product Planning Albert Penello that simply isn't true, and the hardware on the dev kits and the retail boxes is identical, as he clarified across multiple posts on Neogaf.

Not true.

First of all, our Dev kits and Retail kits are exactly the same. The only difference is the SW (Software) running on it.

Second, developers cannot turn off/on CU's (Compute Units). Some of our internal engineers have been able to do that for testing purposes, but it's not something available to developers.

He also explained the presence of an additional port on some dev kits:

Yes. There is a diagnostic port on some dev kits. Still functionally the same as the retail units and made on the same line. To be even more specific, there are several versions of SW for kits based on what's being run. And many of them are literally the same boxes.

In addition to that Penello  specified that he's talking about the current dev kits, and not older ones he's not familiar with.

I'm talking about the current, retail-form factor dev kits. Anything shown on one of the black kits, or white zebra kits. There were very early PC-based dev kits with specs I'm not familiar with, lest I get caught in semantics discussion.

Finally, as a bonus, he threw in a personal guess on why most third parties aren't showing their games  running on actual Xbox One hardware.

You know, I'm not sure. You'd have to ask the 3rd Parties. I was hoping to see more myself.

If I had to make a GUESS (please note the highlighted "guess" as the following statement is made by me personally and not as a representative of the Microsoft (R) corporation), and it's probably because everyone is busy trying to ship in two months. Taking time off to make playable demos may be too time consuming. You've got two new console launches on top of likely 4+ existing platforms.

There you have it, straight from the lion's mouth: If you're inclined to disbelieve what you see at an industry event or convention thinking that it runs on a dev kit, so things may be different with a retail Xbox One, that just isn't the case.

The final guess on third parties is actually very interesting, as it gives a quite believable explanation on what we've seen a lot lately, and caused quite a few concerns on the state of readiness of those third party games.