 Dimensions of an ATX power supply are 150 mm width, 86 mm height, and typically 140 mm depth, although the depth can vary from brand to brand. Dell has not published the dimensions of its proprietary psu (8 pin) for 3910.  Dell uses psu of same 8 pin for optiplex 3000/5000/7000.  It also uses same psu in XPS 8950, for which there is option to upgrade to 750/1000w.  the higher power oem psu are of same height as the 180w psu, but are wider. vendor published data of 750w (10 pin) psu is 185*150*62mm.  It is 150 mm wide and 62 mm tall (and 185 mm deep).  [IMAGE]   [IMAGE] therefore, it is a low profile psu, only 62 mm tall.  A standard 86 mm tall psu would not fit in the space between chassis floor and motherboard. [IMAGE]   The real problem of using ATX psu however is that we still do not have a verified pinout of the Dell 8 pin (a subset of 10 pin for Intel 12th gen oem mobo).  so a standard psu 24 pin has no adapter for the Dell motherboard. for now your option is to use the top 300w oem psu for 3910 which is still good for many gaming video cards.  Those 460w/500w psu for 8950/7000 may not be compatible with 3910 because they have two 4 pin.      
Hi there, I am thinking about purchasing an Inspiron 3910 and upgrade it for gaming on my own.  Most parts such as memory and video card are standard.  However, I have a question about the PSU.  I know that Dell's OEM PSUs are "slim" or Mini ITX (blue box) and they are not powerful enough.  I want to replace with standard ATX PSUs (over 500w).  Is this doable?  I do see that there is space (red box).  Thank you.   [IMAGE]
Upgrade the PSU for Inspiron 3910