Hello I have a toshiba satellite c855 laptop which was factory equipped with an intel b960 processor and now I have replaced it with an intel core i5 3230m processor and it is working for a while but then suddenly you can help me with some information
it came with 4gb ram, 750 hdd, intel 960 processor. at the moment i put 8gb ram 128 ssd + 750hdd in place of optics and i5 3230m processor. after a while he turns himself off.did not stop with the intel b960 processor
Install the original processor back in and see if the problem stops. If so, bad processor or something related to the processor upgrade. If not, remove the drives and see if that helps. If it does, it's related to the drive. If it doesn't, put back in the original ram. If it fixes it, something wrong with the 8gb ram.
there is nothing wrong with memory and drives because it worked perfectly with the original processor. I also tried i7 2gen and 3gen processors but it didn't work properly with them either, and I bought this i5 3230m because according to the description it is compatible
Good. So you didn't damage anything while trying the upgrade.
The only thing I can see that might be the root cause of this is that while the TDP of both your original processor and the i5 is 35w, because the i5 is a 4 core and because it has a higher max temp, the cooling is probably insufficient.
One potential way around this (or to confirm the hypothesis) is to set all the fans for 100% all the time. If this extends the time before it shuts off, then it definitely is a cooling issue, and if it allows it to not shut off, then cooling is the problem.
Check the service manual for cpu replacement procedures and follow that precisely, especially on the application of thermal paste.