How can i do that on a HP z400 with windows10 the bios does not provide any settings regarding overclock. Can i do this via software on windows ? XTU and ThrottleStop dont work i tried them
The HP Z400 can be overclocked using Throttlestop software.I don't know which software tools are to be used, since I've never used a Nehalem CPU. However, I think you should better ask in a true overclocking forum.
The thread starts here.
Throttlestop overclocking Desktop PCs
You do need to have one of the unlocked Xeons. Which one will work in your Z400 depends on which MB you have.
The older ones suppport W3570, W3580 Nehalem based Xeons these have 4 RAM slots. The newer ones with 6 RAM slots use the the W3680,W3690 Westmere based Xeons.
Itseems that TS is the best choice for software OC up to X58 systems, but XTU is better with later CPUs. It's just that's when it was developed.
Here's a newer Xeon overclock in a Dell T3610 workstation using Intel XTU from page 35 in that thread.
I found a way to overclock Dell Precision T3610 + E5 1650 v2!
Installed XTU, TS 8.7. Set up all to unlimited in XTU or 4095 in TS.
Disable C states in Bios, enable speedstep, but in TS you have to disable it!
The only remaining is that you have to do a sleep in Windows, than turn on pc, woalla, your multiplier unlocked!
You need some heatsinks for the VRM to do 4400-4500 MHz(of course you need a decent chip), but with stock cooling the temps peaked at 78 C.
Dell computers (ex mine M4800) can step over TDP limitations, or weak PSU problems , aftermarket batteries when you do a sleep in Windows."
Dell Precision T3610 Performance Results - UserBenchmark