Here is a comparison of the two CPU's.    https://ark.intel.com/compare/88176,97129

This is the Precision 3620 Spec sheet:  https://www.dell.com/support/manuals/pr/en/prdhs1/precision-t3620-workstation/prec_t3620_om_pub/specifications?guid=guid-0a90134e-599f-4abc-b76b-4bbf7c540321&lang=en-us

Thanks grysql.

So, finally the CPU socket can be operational with the Xeon as well as the Core i7, for the same motherboard.

Sorry for this insistence ^^'

No.  Socket compatibility is just the beginning - the system will not boot with an i7 CPU.

Ok ejn63, thanks.

Then, I must buy this workstation initially with a Core i7.

Thanks to everyone.