My current config is: Sempron 3000 939, 6600GT, 4 memory sticks 512 DDR, 2 HDD, 1 DVDRW + 1 CD, floppy, soundblaster, Lan card, Gigabyte k8nf9 all powered by Fortron 350W THA-P. Now i wanna change CPU to X2 4200 and the question is if this Fortron will be enough? According to extreme calculator current consumption is about 300w but with new cpu it rises to about 350w. I wonder why the difference is that much if power requirement of sempron technically is 62W and this dualcore 4200 - 89W? This power supply is said to be very strong and has good 12v lines. However someone adviced me i should change to more powerful. I also wanna change graphic card to something llike 8600gt at least. But as i saw power consumption of this is even lower than 6600gt. All these facts make me so confused. Should i stay with this fortron or buy more powerful? Im not planning any OC at the moment.
When you used the PSU calculator, did you select a single processor? Even though the X2 4200 has two cores, it is still considered a single processor. When I ran it, I got 335W - 364W depending on things like capacitor aging. This suggests that you may want to get a bigger PSU, but it may not be absolutely necessary. Check your PSU label though; that Fortron might be 350W PEAK, but 300W Continuous. If you decide to get another PSU, choose one from tier-3 or better from the list at http://www.tomswiki.com/page/Tiered+PSU+Listings?t=anon.
You can risk it, but chances are high it will not be powerful enough.
My single core A64 s939 2x512MB DDR, 6600GT, with 4hdds (2xSATA, 2xPATA) and a SATA dvdrewriter (no extra addon cards) was not happy with 350W. But it was not the a quality PSU. (I had to remove the PATA drives) until I got a 450W unit.
I think you should upgrade the PSU just to be on the safe side.