The cpu must be supported by the BIOS/EFI of your laptop also. So you need to check what is the list of suppoted cpu of your laptor model.
Sometimes you only need to update the BIOS to the last version to get last processor support.

More research done. On intel page it says that T7250 is PPGA478, while P8400 is PGA478. So although it fits on socket like own, it could be incompatible electrically.

Finding information on my laptop model is impossible, it's was a obscure producer than doesn't exist anymore.

What are my safest options for low power cpu for my laptop?

If cpu-world list incorrect, I don't know if I can trust other websites.

Yet more research, on wikipedia page:
https://en.m.wikipedia.org/wiki/List_of_Intel … re_2_processors

T7250 is socketP it says, I have SLA49
P8400 that I bought is also socketP it says, I have SLB3R.

Maybe this new cpu is dead?
Pressing power button, P8400 gets hot much faster than T7250, and shuts down. Nothing shows on screen.

Try looking up the manufacturer (of your laptop) specification for supported processors.
If the maker of your laptop never released a product in that series with support for the chip in question, then they had zero reason to ever write a BIOS to provide support for it.

You can't use P series cpus if the motherboard chipset is pm965, It only works with pm45 chipsets.
run cpu-z and check what chipset you got under the mainboard tab.

Karbist wrote on 2023-03-29, 17:19:

You can't use P series cpus if the motherboard chipset is pm965, It only works with pm45 chipsets.
run cpu-z and check what chipset you got under the mainboard tab.

Ran cpu-z, it's pm965.

Karbist, what is lowest tdp cpu that I can run then? I don't care about performance, just low watts of heat.

I don't think it exists in T series.

Never really been into "modern" hardware modding etc, but this is too bad.

I thought it would be easy to replace T7250(35W) with a lower power compatible(~25W).

*demoralized*

PlaneVuki wrote on 2023-03-29, 16:24:

More research done. On intel page it says that T7250 is PPGA478, while P8400 is PGA478. So although it fits on socket like own, it could be incompatible electrically.

Even if CPU and motherboard have the same socket electrically doesn't necesserily mean they are compatible with each other. BIOS and chipsets are important factors.

Example: I've got quite a few CPU and boards using LGA 775, the socket of longest lifespan. Among them, the oldest is Asus P5GDC-V Deluxe (with DDR/DDR2 dual memory slots) using P4-520, while the "newest" is Asus P5G41T-M LX (using DDR3) with Q8300. Both boards support late 90 nm "Prescott" CPU e.g. P4-670, but you simply can't install Q8300 on P5GDC-V Deluxe, or P5-520 on P5G41T-M LX. Furthermore, neither motherboards support Core 2 Extreme processors, but I've got another Gigabyte GA-P31-ES3G that supports QX9650 (although I don't have one).

Of course I gave up on P8400. Iı also was somehow an "upgrade", it's Penryn series instead of my T7250 Merom.

But trying to find another cpu that could work, while having lower tdp.

Now I am checking 3 websites for each cpu: cpu-upgrade, cpu-world, intel.

Looking at https://www.cpu-upgrade.com/CPUs/Intel/ ... et_P).html

I can see that there are 27W celerons can be a possibility.

Looking at celeron m 530 specifically:
https://www.cpu-world.com/CPUs/Celeron_ ... 30SR).html
and
https://www.intel.com/content/www/us/en/produ … ifications.html

Cpu-world says 27W / 31W
Intel page says 30W.

30W and 31W are not significantly low compared my current 35W (T7250).

But 27W could be of some interest.

What can you suggest me?
Why are there different values for tdp, 27/30/31W?
and how can I identify a 27W cpu from sales?

AFAIK, every mobile Intel CPU since Mobile Pentium III supports Speedstep. You can use a software utility to lower the CPU speed / voltage and reduce heat. I would think that is better than replacing the CPU.

bakemono wrote on 2023-03-30, 09:33:

AFAIK, every mobile Intel CPU since Mobile Pentium III supports Speedstep. You can use a software utility to lower the CPU speed / voltage and reduce heat. I would think that is better than replacing the CPU.

bakemono, thank you for advice. In this topic I am aiming at replacing my T7250 with lower tdp compatible cpu, not to achieve lower heat through software. But I was planning to have a separate topic for that at some time later, will be glad to read your posts. (I took note of your speedstep suggestion.)