Juanchioo :
hey i want to know what its better and why have a bottom mounted power supply or have a top mounted power suply
Funny... I was looking for the exact opposite (see
here). I've been looking for a good case which has Power Supply at the top. They are hard to find these days.
Advantages of top-mounted power supply:
* Hot air rises so the area at the top of the case gets warmer and warmer which leads to higher ambient temperature inside the case. This heat at the top needs to be throw out. Power supply is the best component to accomplish this task since it has a fan underneath it sucking the heat into itself and simultaneously another fan throwing the heat out of the case. Most of this heat comes from the CPU and Graphics card which are directly below it.
Disadvantages of bottom-mounted power supply:
* Need to add a fan near the top of the case to remove the accumulating heat at the top. Clearly one fan sucking air out is not better than two fans that were present had the power supply been there. Adding extra fans will also generate more noise to the system. Why add extra fans when power supply could have done this job without extra fans.
* Cable management can be difficult.
* Heat generated from the power supply rises and heats up the graphics card.
* Bottom-mounted power supplies have the fan facing down towards the floor. This will cause them to suck in dust and debris from the carpet and the surrounding, which will eventually clog the power supply up and thus generate more heat and lower efficiency.
* There isn't enough room at the bottom of the case (low ventilation) for the power supply to suck the air efficiently compared to the power supply being at the top. Air has to be sucked through tight spaces around the case into the power supply. This will also increase the suction of dust and debris from the outside due to increased pressure.
You might say that you could turn the power supply upside down at the bottom of the case. But some cases don't allow you to turn the power supply upside down due to the fix screws on the case. Also, turning it upside down wouldn't be as effect as throwing warm air out of the case had the power supply been mounted at the top because that's where the warm air is, which needs to be thrown out.
I would never buy a case with the power supply on the bottom. So why are most cases these days with power supplies at the bottom? Simple: customer demand - and thus sales.
Tomshardware had documented the disadvantages of a bottom-mounted power supply in an article here:
The Problem of Bottom-Mounted Power
and earlier discussion here:
Todays Hot Mod: Reverse PSU Cooling