Yeah but - 10W all getting radiated inside a single 12x12mm BGA package? Isn't that a lot? It sounds to me like that'd be running very hot...
I had a project with a Raspberry Pi2 which was only drawing ~2.5W all up (including the wifi dongle), and it got flaky when the sun shone on the case and got it a bit warm.
Fwiw my 486dx2-66 had a fan, and when that fan died we noticed because of corrupted memory crashing the system. Compared to modern CPU coolers it was downright tiny, but required.
From memory though, they were closer to 20mm or 30mm square though, right? (At least the outside package which I'm assuming is what the 12x12mm spec is referring to)
I had a project with a Raspberry Pi2 which was only drawing ~2.5W all up (including the wifi dongle), and it got flaky when the sun shone on the case and got it a bit warm.