[CPU Upgrade] HP ProDesk 400 G1 MT problem

[Terminator90]

Hi everyone, I'm new here.

I have an HP ProDesk 400 G1 MT with an Intel i3-4130. In order to get a performance improvement, I decided to change the original CPU with an i7-4790. After the CPU change, the computer runs fine... until I reboot it.

During the reboot process, the computer seems to be blocked and the only way to shutdown is to press the power button. Searching the web, I found other people have the this strange behaviour:

https://h30434.www3.hp.com/t5/Desktop-Ha...-p/6055225

https://h30434.www3.hp.com/t5/Desktop-Bo...-p/6620378

https://h30434.www3.hp.com/t5/Desktops-A...-p/5316292

https://linustechtips.com/main/topic/534...otrestart/

Obviously I have installed the latest BIOS version (02.56 Rev.A). You can find it HERE.

The same CPU in another machine works well. I've tried also an i5-4590 but the problem is the same.

This problem is OS indipendent because if I press Ctrl+Alt+Del in the BIOS in order to restart the computer, the problem persist.

It's very hard to believe because this computer is sell with this two processor (i7-4790 and i5-4590). So why there is this problem ? Is it a BIOS lock feature ? Is it possible to have a new BIOS with support both of the CPUs ?

[DeathBringer]

Can you enter in BIOS in your i7-4790?
Post screenshots of first (CPU) & third (Mainboard) tabs of CPU-Z with supported CPU.
Make a photo of this motherboard near a socket.

[Terminator90]

Hi @DeathBringer,

first of all thanks for the answer. Yes, I can enter the BIOS with the i7-4790. Attached a photo take when I had installed the CPU for first time. Also, the power supply is the original HP equipment (300W) and I think is enough considering that this computer have only the integrated graphics.

[DeathBringer]

Can you disable Turbo Boost in BIOS?
Remove heatsink and make photos again.
Have you any discrete graphics card for test?

[Terminator90]

Hi,

no, I can't disable the turbo boost from the BIOS (the options available are in the photo below). I've also tried to disable some of them with no luck. The i7-4790 is working great in another computer with the integrated GPU. Anyway yes, the graphics card slot is working (tried some weeks ago just for test with a discrete graphics card).

[DeathBringer]

You need to test your system with i7-4790 and any discrete graphics card.

[Terminator90]

I've installed the i7-4790 again paired with an AMD 5450 HD. This discrete graphics card have a low TDP, so I don't need to change the PSU. Unfortunately, the problem persist. The computer boots up, recognize the processor, enter in the BIOS and when I try to reboot with the combination Ctrl+Alt+Del the screen became black and nothing happen. I think it should be some BIOS lock feature.

[DeathBringer]

OK. Enter in BIOS with new CPU, then go to Save & Exit and do Restore Defaults, then Save Changes and Exit.

[Terminator90]

After that procedure, the issue is still present. Also, in order to reset the CMOS values, I've tried to remove and reinsert after a minute the CMOS battery and then press the yellow button on the motherboard. Nothing. It's incredible that only the reboot fail and for the rest it work perfectly.

[DeathBringer]

So I have no more ideas.