Supported CPU not working 3 long 6 short

[Matjager]

Hello,

I have a i7-9700 HP Z2 Mini laying around. I used the CPU for my sons PC and found an i3-8100 SR3N5 CPU. According to this PDF  and this page this should work. But after installing the CPU and clearing the CMOS I get 3 long beeps and 6 short beeps telling me that the CPU in unsupported. Am I doing something wrong? I would like to revive this PC.
If I need to buy another CPU I don't want to have the same issue again. So please advice.

[BeemerBiker]

Try resetting the CMOS

Unplug from wall, tap the power on  switch a few times to discharge residual electricity then hold down the CMOS reset switch for 15 seconds.

Before reaching into the motherboard area, touch your finger to the metal case to discharge any static electricity.

[Matjager]

Thank you for your advice.

I tried what you said. Unplug power, do some power cycles and clear the CMOS. 

I already did that before, but can't hurt to do it again.

Still when I boot up the machine I get 3long beeps and 6 short beeps.

Is there anybody who experienced this before and got this fixed?

[BeemerBiker]

Take out the CPU and look for any bent pins in the socket.  Look for corrosion on the CPU contacts also.. You will need a light source and a magnifier, preferable one on a stand with the light source built in.

The above looks like the author accidently dropped the CPU on the socket.  The above can be repaired but it is difficult and requires a really steady hand in addition to a few tools.  Sometimes the damage is not obvious and you have to hold the socket at an angle so that the light shows a change in the reflection pattern.

Coolant leaks and HS compound stuck in the pins usually renders it unrepairable IMHO.

P:ossibly reseating the CPU after cleaning the gold contacts on the CPU may fix the problem. 

[Matjager]

I checked the pins on the motherboard and they are all inline. I also cleaned the CPU with IPA. I think that if there was a bent pin the CPU would not be recognized and then the PC should beep 3-4  in my opinion. A 3-6 means unsupported CPU so the machine can identify the CPU.

[BeemerBiker]

CPU should look like the one below, easily readable no other marking

Does the CPU get warm when you turn the PC on?  Press your fingers against the surface and press the power on button. Be prepared to unplug the power cord quickly.  It should feel warm immediately and get hot within 3 seconds like a 60 watt incandescent bulb.

The latest BIOS update for your Z2 G4 is dated March 2024.  You could put the original i7 back in and try updating the bios

https://ftp.hp.com/pub/softpaq/sp151501-152000/sp151866.exe

You could try removing the CMOS battery in the unlikely event that switch was defective.