It is really a challenge to find such important information in the Intel web site ... I would like to know the number of registers in the Intel Xeon X7542 architecture.
ark.intel.com is the usual initial source for CPU model identification. As it is a Nehalem family CPU, the registers are the same as any Nehalem. That site gives you links to plenty of technical reading.
>>... plenty of technical reading...
Also take a look at: