Hello PRATAP, thanks for joining the Processor community.
I would like to inform you that the I5-3450 is not found on the compatible list of the DH61AG motherboard. Compatible Processors
It is important to tell you that if you are using the Standard Low Profile Intel Boxed Thermal Solution for Thin Mini-ITX HTS 1155LP, and the processor reaches the maximum TDP, you may experience some overheating issues.
Please check this link for additional information on this heat sink. Check point #3 on the System Requirements. http://cache-www.intel.com/cd/00/00/49/20/492064_492064.pdf
If you want to continue using this processor, I would recommend you using another heat sink, a Noctua for example.
I have gone through the link reg. Intel Thermal Solution HTS1155 LP. But i am using a chassis called Mini-Box.
It cant accommodate. On the other hand Noctua is very heavy.
I have got i3-3220 processor with ASUS mother board (can take upto 77W) in another system. So i will change both these.
ASUS H61-M-CS with i5-3450 and DH61AG with i3-3220.
I am very much confused why many models are there in one kind of processor?
I have Gigabyte Mother Board GA-H97N-wifi with i7-4770.
Can you explain please which one should i select low TDP or high TDP and what are the factors?
According to GIGABYTE, this is the list of supported processors http://www.gigabyte.com/support-downloads/cpu-support-popup.aspx?pid=4992
This board is totally different Pratap, since it supports all i7-4770 versions. Therefore a processor with low or high TDP will work just fine.