From the Optiplex 790 Tech Guide:  [IMAGE] Max spec CPU is the I7-2600 .  According to userbenchmark, that also looks like the max CPU others are using also.  
So I am using a Dell OptiPlex 790 Series. Pre-Installed with Windows 7 Professional, Upgraded to Windows 10 Pro, & upgraded to Windows 11   Computer Specs: Processor: Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz   3.10 GHz (2nd Generation) Installed RAM: 8 GB (7.88 Usable) Operating System: Windows 11 Pro Architecture: 64-bit operating system, x64-based processor   I have three questions to ask about this desktop. Is there any maximum intel processor it can reach? I am on the BIOS A18. But it doesn't support Secure Boot, & TPM 2.0 is not available since it only has a TPM 1.2 Module. Is there any way to get Secure Boot Enabled, TPM 2.0, & an Intel processor that can reach the maximum it can go?
Dell Optiplex 790 Maximum CPU