If not, what was the earliest generation of Intel Core to support memory rank interleaving?
Is there any performance difference between using single-rank or dual-rank memory with the i7-960?
I think you are jumping ahead of yourself. If the processor is upgradeable at all, the manufacturer of the board still defines what memory can be used. So, you must use what the board specifies.
Now, upgrading the processor? You must ask the motherboard or system manufacturer what processors are compatible with THEIR BIOS. Then, you can select from those.
Personally, for an 11-year old system, I would not bother with such an upgrade. It is not going to do anything for you, and will not be supported by Windows 10.
I am not looking to upgrade the processor. I would like to get the extra RAM (going from 12 GB to 24 GB) to support larger data-sets in engineering simulations. The 4 GB DIMMs (to replace the six 2 GB DIMMs) come in single-rank and dual-rank configurations, but are otherwise the same. I get that the performance difference is probably small between SR and DR DIMMs, but it got me thinking. Are single-rank or dual-rank modules better from a performance standpoint? Since the i7-960 has an integrated memory controller, I figured this is a processor question more than a motherboard question. But, I haven't been able to find a clear answer either way regarding the performance trade-offs between SR and DR. I have a feeling any performance benefit of DR over SR is due to rank interleaving. Yet, I'm not sure the i7-960 does rank interleaving. Hence, the question.