XPS 8940, PSU upgrade to 850W that fits inside the case

8940 stock psu is a modified TFX with dimensions 85x65x225 mm.  (standard TFX is 85x65x175mm)

D500E005P H500EPM-00 0Y7R0X 8.5*6.5*22.5cm https://www.ebay.com/itm/For-Dell-500W-Power-Supply-D500E005P-H500EPM-00-0Y7R0X-8-5-6-5-22-5cm-/392901055982

looking at 8940 case, it is not mandatory that psu upgrade has to be TFX in order to fit inside the case. when looking at stock psu, the narrowest dimension of 65 mm wide is the actual physical restriction due to motherboard in proximity, but there is no restriction of a psu to be 85 mm high. In fact it can be quite a bit taller than 85 mm (up to the width of case,169 mm). There is no other component in the case restricting this dimension.  


8940
In comes 850 W SFX psu by cooler master, V850 SFX Gold. DIMENSIONS (L X W X H)100 x 125 x 63.5 mm
not only is its width of 63.5 mm compatible with 8940 case (< 65 mm), its other two dimensions can fit inside the case with ease.  you just cannot screw mount it.
https://www.coolermaster.com/catalog/power-supplies/v-series/v850-sfx-gold/

Silver stone SFX 1000W

125 mm (W) x 63.5 mm (H) x 130 mm (D)

https://www.silverstonetek.com/product.php?pid=965&area=en

Silverstone Technology 800W SFX-L

Corsair SF750

Seasonic Focus SGX-650

Corsair SF600

Installing Cooler Master in XPS 8940 case.  Power plug access is not blocked.

V850 SFXXPS 8940

Not clear if you are thinking of replacing the 500W power supply you have, but if so, why? are you having issues with your XPS? If so, what issues? Is the PSU running hot? shutting down? Are you running max RAM, top end GPU, added more SSD ? what's the thinking of replacing a 500W unit? It won't make the system run cooler.. 

thanks

Scott

This discussion topic is for general community users who may be interested in psu upgrade for higher power gpu but fettered by TFX form factor of stock psu.

Has anybody actually made the swap? Could a bracket be 3D printed to secure the PSU? 

I purchased an XPS with the i9 k and 3060ti. Nvidia says recommended 550w for GPU. Why would dell even offer this if it doesn’t meet recommended specs of GPU sold stock with the PC? I added 2 92mm Noctua fans, 1 replaced the case fan and 1 is mounted in the front of the case below the HD. Keeps it pretty cool. I got a good deal and cheaper than building my own since GPU prices are so out of whack. Thinking of buying a better cooling case and new motherboard in the future that can really let the i9 shine. Any suggestions would be great.

Re: I purchased an XPS with the i9 k and 3060ti. Nvidia says recommended 550w for GPU. 

Nvidia recommendation is often overestimated.  online psu calculator estimates 424W.

So most Psu’s can fit but I’m more concerned with the 6 pin connection that powers the motherboard. Specifically is this the same as a 6 pin PCI-e cable or do I need to but a 24 pin to 6 pin adapter? (Does this make sense?) I can’t find any difference between a 6 pin PCI-e and a 6 pin atx power cable (The one that goes into the motherboard) but that doesn’t mean there isn’t one. What cable are you plugging into the motherboard?

8940 psu 6 pin power connector pinout

pinout (flip the connector plug to face you with latch on right side, pin left 123, right 456)

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

8940 motherboard 6 pin socket (right 123, left 456) is keyed

1 square.      4 bevel.
2 bevel.        5 square.
3 bevel.        6 square.

compare to 6 pin PCIe socket (right 123, left 456) pin 5 key is different

1 square.       4 bevel.
2 bevel.         5 bevel.
3 bevel.         6 square.

A 6 pin PCIe power connector can in theory be plugged in 8940 6 pin ATX socket because its pin 5 is beveled which can fit a square socket hole.  Electrical pinouts are completely incongruent.  Luckily the 6 pin PCIe will have no power because the 24 pin of psu has no where to plug in, thus psu is not turned on.

There are ZERO options for upgrade AND the MODDIY Adapter is not validated to work.

The G5 and 8940 power supply are not upgrade-able

The six pin connection is completely proprietary as are the dual 4 pin connectors.

@redxps630  there are zero confirmed updates for this.

The supplies are NOT TFX they are proprietary.

@DELL-Chris M  you should weigh in on this because telling users they can upgrade is completely false.

@Dell-BradL giving false hope to users should be a rule that is prevented on the forum.

Using Buzz words like ATX or TFX or any other standard is very bad advice in regards to the proprietary Dell Design.

Thanks for all the info guys! I knew there was something different and didn't find the correct thread (https://www.dell.com/community/XPS-Desktops/XPS-8940-VRM-question/m-p/7819596#M58322) until after posting. Sorry for taking a week to respond as I kept changing things.

As for most psu's "fitting", I was wrong as ATX size psu's are too tall. Sfx size psu can sit inside the case but only dell's psu's "work" with the case without modifications and using the original screw holes. You will also have cooling issues if it is against the back of the case so I am working on 3d printing a "funnel" to hopefully not limit the psu cooling (as much, nothings perfect) and allow the psu to sit in the middle-bottom of the case (still need a mounting system).

Having it sit in the middle-bottom of the case would also keep my GPU (a short gtx 1660 supper) and the sfx psu from drawing air from the exact same location. I am also hoping on keeping the load on the psu low enough that psu cooling isn't a major deal anyway. 

I am also trying to do this without modifying the case and will try to update this thread as I make process/ find round blocks.

Here is a picture of the prototype funnel (will shorten it so it sits under the motherboard and fix some other dimensions) and the SFX should completely fit the funnel opening. I will update once I finished installing a SFX psu once my psu arrives and I get the funnel updated.

@Onefunkydude   What SFX PSU are you buying and which of the various SFX form factors is it?  I gather that SFX power supplies can be standard profile, low profile and PS3 profile.  Also, how are you managing access to the power connector and on/off switch?