XPS 8940, ATX 6 pinout

To upgrade to standard 24 pin psu, use moddiy 24 to 6 pin adapter for optiplex 3050/5050/7050 (same 6 pinout), or mod 24 pin DIY.

https://www.moddiy.com/products/Dell-OptiPlex-3040-3050-3060-Main-Power-24-Pin-to-6-Pin-Adapter-Cable.html

• 2 yellow wires (24 pin) –> 2 blue wires (6 pin)
• 2 black wires (24 pin) –> 2 black wires (6 pin)
• 1 grey wire (24 pin) –> 1 grey wire (6 pin)
•  Short green and black wire (24 pins)

6 pin plug

flip the plug to face you.

1 +5V PS_ON Blue.     4 +5V PWR_OK Gray
2 COM Black.              5 +12VBDC Purple
3 COM Black.              6 +12VBDC Purple

CPU 4 pin x 2 socket on 8940 motherboard, use psu 4 pin connectors (2 brown +12V, 2 black Gnd)

1. processor power-cable connector (ATX CPU1)
2. processor power-cable connector (ATX CPU)

the two connectors are identical in beveled key, both ATX 12V. 

When using aftermarket psu for G5 CPU and CPU1 connectors, one needs to connect two cpu cables to both cpu1 and cpu2 ports on psu side.  connect only one split 4 pin ATX 12V connector of each cable on motherboard side.

8 pin EPS to 4+4 pin ATX-12V adapter.  this allow psu EPS 8 pin to connect to 4 + 4 pin CPU on 8940 motherboard.

EPS 8 pin to 4+4 ATX 12V

note this Y adapter is different from split EPS 8 pin to 2x4 pin.

a true ATX 12V connector has beveled pin 2/3 and square pin1/4.

ATX-12V

https://www.coolerguys.com/products/8-pin-eps-molex-power-male-y-to-2-4-pin-pentium-power-eps

It seems possible to plug unsplit EPS 8-pin connectors from standard modular psu directly into 4-pin CPU sockets on 8940 motherboard.  This is made possible because 8940 board is designed to have some empty real estate space around the 4-pin.  This is definitely true for the right sided 4 pin.  For the left sided 4 pin, there is tight space between it and hard drive cage, thus not sure.

It is verified that unsplit 8-pin EPS connector can plug into 4-pin socket using pin1,2,5,6, leaving pin3,4,7,8 hanging in air not connected.

8940 4-pin CPU

more evidence that XPS 8940 and optiplex 3050 psu are compatible.  Therefore feel confident that 24pin-to-6pin adapter for 3050 will work for 8940.

Dell-Chris M posted FAQ XPS 8940

PSU
2VD0G 360w Liteon

google this DP/N 2VD0G

02VD0G 360W Power Supply Unit For Optiplex 3050 7050 3668 MT

of note, the 360W psu has 6+4 pin: it has only one 4-pin connector which can plug in CPU1 socket in XPS 8940.  This is compatible with its 360W rating.  In other words, when you do not need to push cpu power consumption in 8940, you can leave cpu2 empty and only plug in CPU1.  This is a known optional practice.  For example, high end ASUS or EVGA x58 board has two 8 pin EPS sockets, but you are not required to plug power into both.

Gday RedXPS630 I was wondering if you could just run 4 pins on the 6 pin connection (the 2x 12v and the 2x Com)??? I am trying to modify a 1200w psu to utilise this connection and am unsure what to run to pins 1 (PS_ON#) and 6 (PWR_OK).

Any assistant would be grateful. 

If you have a 1200 w ATX 24 pin psu just use Amazon 24 to 6 pin adapter. It will take care of the PS ON and PWR ok in the 6 pins for you.  You must have all 6 pin in Dell proprietary connector wired.  Skipping some wire connection will likely render pc no post.

https://www.amazon.com/gp/product/B08M5BZ6P8/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

for the dual cpu 4 pin, some psu already provide such pair.  If your psu has only EPS 8 pin you can use an EPS 8 pin female socket to dual cpu 4 pin male connector adapter.