Thank you for contacting Intel.
The main difference between the Intel® PRO/1000 MT and PT Server Adapter is the form factor. The Intel® PRO/1000 MT Server Adapter 32 and 64-bit PCI-X slot, while the Intel® PRO/1000 PT Server Adapter support PCIe v1.0a slot. The M and P stands for the series model while T stands for the type of port which is copper (1000Base-T).
I would also like to inform you that these two models have been discontinued. For more information, please refer to our websites:
1. Compare Intel® PRO/1000 MT and PT Server Adapter - ARK | Compare Intel® Products
2. List of Intel Network Adapters - ARK | Intel® Networking Products
I hope I was able to address your concerns. In case you have other questions, please feel free to write back.