good to know, wanted to know if i7 is a possibility.
you can get 6 core i7 cheaper on ebay. even used to make the saving significant.
what would the ECC loss do to the system and performance? would you have to to use non-ECC RAM as well?
Further to the comments above if you were to use an i7 you would have to use non ECC memory or the system will not boot.
Hyperthetically comparing the same speed RAM in ECC and none ECC formats you may see a small increase in performance by using the latter due to the reduction in overhead from the validation process. Likewise energy consumption may improve slightly as circuit wise non ECC memory is much simpler with less to do per chip.
The reason I say the above are hyperthetical is that any gains will be dependant upon how Apple have designed the system they are placed in and how the user deploys the chips in the system.
For most computing, except 3D and scientific computation (there will be other use cases I sure), the loss of ECC memory has no real side effect.
With regard the FirePro cards I'm sure I read, like the poster before me, about some quirk in how AMD deploy the ECC memory on the cards. 2 things I believe I have heard and I'm sure someone else can clarify a) AMD use a form of virtual ECC memory on the cards, it does the same thing but is not a true hardware solution on a per module basis b) the FirePro'esque cards used in the Mac Pro forego the ECC solution altogether (probably a cost saving).