Does Cortex-A12 not supprt AMBA4 ACE protocol?
The figure and description of the Cortex-A12 product page(http://www.arm.com/products/processors/cortex-a/cortex-a12-processor.php) shows as if it only supports "AMBA4 AXI Bus" is available bus interface.
So, CA12 not support ACE means:
CA12 could not be used with CA7 in a big.LITTLE design?
Correct - the big.LITTLE equivalent of this would be a pairing of Cortex-A17 with Cortex-A7.
HTH, Pete