I'm looking to upgrade a GPU in a dell studio slim 540s from a HD 3450 to a HD 7750 Low Profile.
The thing that concerns is that the computer uses a 250 watt PSU.
The eXtreme Power Supply Calculator recommended a 259 watt (and minimum of 209) PSU with the new graphics. I was wondering if this is accurate and if i can stretch the PSU 9 watts and use this graphics card without a new PSU.
Intel Core Duo E7200 @ 2.53 GHz
4 x 1gb ddr3 ram
ATI Radeon HD 3450--changing to-->SAPPHIRE Radeon HD 7750 1GB Low Profile
Blu-ray Reader Drive
250 watt generic PSU
I just about 99% sure you will have no issue with the upgrade most psu over calulate the power draw. If your really concerned you probably can pick up a cheap watt metter at say home depot and see how much power your PC actually draws.
Total Power Supply Wattage is NOT the crucial factor in determining power supply adequacy!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most critical factor.
Since most of the systems power consumption is from the power supply's +12V rail you need to make sure that you don't exceed what that 250 Watt PSU is capable of supplying.
The 250 Watt TFX form factor PSU in the Dell Studio 540s should have a maximum combined +12 Volt continuous current rating of 17 Amps.
The Radeon HD 7750 should draw less than 4 Amps from the +12V rail. That would leave 13 Amps for the rest of the system which should be sufficient based on your 65W TDP CPU.