We have two identical systems here, each one consisting of:
1x 5016I-MTF
1x Xeon 3450
2x 4GiB DDR3-1333
4x Seagate 500GB HDD
One system has a "SNK-P0046P" while the other system has a "SNK-P0046P (rev B)". The system with "SNK-P0046P" hits the TJunction temperature easily under load.
I've swapped the heatsinks between those two systems -> now the other system gets to hot. So I would say that the "SNK-P0046P" is not capable to keep a Xeon 3450 cool enough...
"SNK-P0046P (rev B.)" is ~20 degree colder (compared to "SNK-P0046P"), tested with both systems.
SNK-P0046P without a revision is engineering sample. Please discard engineering sample and use mass production SNK-P0046P Rev. B.