Which size 790? There are 4 diff model 790's.
Do a search in the Optiplex forum. This question is answered lots of times (by Speedstep.) See this one
Speedstep is delusional, he thinks anything other than an EVGA 700Watt BR is "insufficient" and even that evga 700br is "bare minimum"
IDK what he is smoking, but a 700watt PSU is a bit overkill to replace a 265w PSU
Looks like it works
|DC output||+3.3V / +5V / +12V / -12V / +5Vsb / Total
24A (140W) / 22A / 58.3A (700W) / 0.3A / 3A / 700W
|Main||(1) 24(20+4) Pins|
|CPU||(2) 8(4+4) Pins|
|Peripherals||(3) 4 Pins|
|S-ATA||(8) 5 Pins|
|PCI-E8||(4) (6+2) Pins|
|Dimension||160 x 150 x 86 (mm)|