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CPU for Dell Optiplex 780 DT (400+ watts) Please help me

Last response: in Components
February 15, 2013 7:52:34 PM

I've probably spent days researching different PSU's and graphics cards copatible with this computer.. I would sure appreciate any advice.

Here's what I'm working with:

Dell Optiplex 780 DT (not Mini Tower or SFF one - its kind of a cross between the two and the case size presents problems with PSU - Also the mini Dell motherboard connector - wont work with most PSU.

I am trying to A) find a 400 or 450 watt PSU that will connect to motherboard (fitting in case would be nice however I am open to having the PSU outside the case if need be B) will a Sapphire Radeon HD 7750 1GB DDR5 Micro HDMI/DVI-I/Mini DP Low Profile PCI-Express work with the motherboard - i know hyperspin doesnt require a high end vid card however i wanted to see if PS2 roms would play smoother and possibly some games - primary use is for XBMC and Hyperspin

(see below specs)


Intel® Core™ 2 Duo E7500/2.93GHz, 3M, 1066FSB <-- DT is the case size (i have this mb see specs)

The PSU is killing me. I know they make ATX 24/20 pin big to mini adapters but Dell has dif pin settings etc. .

Any help would be greatfully appreciated.

a b ) Power supply
February 16, 2013 11:44:33 PM

Not all but some Dell models have a power supply with a different pin setup. On those models, if you plug in a standard atx psu it will start a fire. You have to check out the pc power and cooling PSU recommendation for Dell systems at to find out.
a b ) Power supply
February 22, 2013 8:33:40 PM

My deepest condolences man, this PSU doesn't look good and not easy to find.

I will find the way to post unresponsive links - Dell just removed a lot of documents from its servers....

This is the PSU Removal Guide so you can see more details

This is 255 watt PSU. Lets see if we really need to look for an upgrade according to the Extreme Power Supply Calculator, I used your approximate data

System Type: 1 physical CPU
Motherboard: Regular - Desktop
CPU Socket: Not Sure - Show All CPUs
CPU: Intel Core 2 Duo E7500 2933 MHz Wolfdale-3M
CPU Utilization (TDP): 90% TDP

RAM: 4 Sticks DDR3 SDRAM
Video Card 1: AMD Radeon HD 7750


Regular SATA: 2 HDDs

DVD-RW/DVD+RW Drive: 1 Drive

USB: 2 Devices

Regular: 2 Fans 92mm;

Keyboard and mouse: Yes

System Load: 90 %

Minimum PSU Wattage: 198 Watts
Recommended Wattage: 248 Watts

Even this way you are passing with your original 255 watt PSU, also consider the fact that generally Dell PSUs are under rated!

You saved, just get your card and enjoy your life, no worries.
Related resources
February 25, 2013 6:00:01 PM

AMD Radeon HD 7750

3DMark GPU Score:







45 3DMarks / W

I am going to try putting this in my 780DT when I get home, not sure why i thought i would need 400Watts minimum for this card.

i bought a Dell 400W psu that people have used with other optiplex models - im hoping since its dell it will have the mini motherboard connection.

If im using 2 extenal hard drives with the computer does that affect the PSU needs
a b ) Power supply
February 26, 2013 12:46:36 AM

I used 2 SATA hard drives in calculation, so you are ok, which PSU model you got? Would it fit?
March 6, 2013 6:04:04 PM

Kisianik said:
I used 2 SATA hard drives in calculation, so you are ok, which PSU model you got? Would it fit?

The Radeon HD7750 works fine with the origional psu (and yes I did unplug the cd rom and put a sata hdd in - so 2 hdds in comp) Got a disk failure warning and i imagine it is due to the psu load. I also want to eventually upgrade the cpu to a quad core which i would imagine would take a higher watt psu.

So heres where i am (wiring pinout above for both clips to MB)

F5114-350W - Dell F5114 400 Watt Power Supply Upgrade

Product Description:
This 400 watt power supply was retrofitted to fit in place of your original F5114 power supply. It mounts in the same place as your original power supply and uses two screws to hold it in place. This power supply is required to replace power supplies in Dell Optiplex GX280 SD (Small Desktop) computers and others. This power supply has all of the special dell connectors needed to get your GX280 SD back up and running. Plus this power supply was specially designed with a PCI Express plug just for that new video graphics card you may be installing.

Technical Specs:

5" Wide X 2.5" Tall X 4.75" Deep
One ATX Connector (20/24 pin)
One P4 Connector
Two PCI Express Connectors (6-pin)
Four Molex Connectors
Three Sata Connectors
One HP video Connector
One 6-Pin AUX Connector
One Floppy Connector
One Dell 6 pin Connector
Weight: 3.0000 lbs
Output Max. Load
+3.3V 12A
-12V 0.8A
+12V 20A
+5V 21A
-5V 0.5A
+5Vsb 3A

I cut the wires from the origional PSU bc of the smaller connector to motherboard. I am carefully looking at the pin layout for both psu's and i am going to splice the wires together.

The thing that throws me off is that the brown and orange wire are in the same pin on the larger atx clip, on he Dell optiplex small one the brown one has its own pin. Also the seperate 4 pin part on the larger atx clip has orange yellow red black, this is not mentioned on the above pin out.

Another question: if I connect a red wire to a red wire (provided its all equal) does it matter which red wire to which red wire etc or is it specific? I am trying to avoid destroying the motherboard and more importantly creating a small fire in my 2 bedroom condo - I do have a little experience with similar tasks. I put a wire with a black one in my light unit a week ago and the light blew and the box near it - embers everywhere and complete blackout :ouch:  - I realize that was stupid, so im asking now before i fiddle with things..
March 6, 2013 6:14:43 PM

Kisianik said:
I used 2 SATA hard drives in calculation, so you are ok, which PSU model you got? Would it fit?

Here is a larger picture of the pin layouts - the top being the clip that i am attaching to the 400w psu (top is layout for optiplex 780dt, bottom is diagram for the 400 watt dell psu i bought that had a standard atx sized clip)

a b ) Power supply
March 7, 2013 3:18:17 AM

First impression of you - :pt1cable:  WHOAAAA :pt1cable:  , you going nuts with power supply, well my deepest respect for you for doing this, no joking this time. :sol: 

I would probably look for 24 to 20 pin adapter in this case, but it is too late now, good luck!
November 18, 2013 7:57:49 PM

I'm running a SAPPHIRE ATI Radeon HD 7750 1GB GDDR5 LOW PROFILE which was advertised on ebay for AUD $154. I got it because the onboard Intel GMA 4500 MultiMedia Accelerator chip isn't adequate for some games. The 7750 is 10-29 x faster than the GMA 4500. The 7750 maximum power draw is 55W. This is well within the PCI-E slot limit of 75W.

The computer is a Dell Optiplex 780 3.3 GHz Core 2 Duo with 2 x 2 Gb DDR3 RAM. Windows 7 Pro 64 bit. I bought it ex-lease for $220. The 265W power supply doesn't even have a PCI-E 4 pin or 6 pin connector. So the graphics card has to draw all of its power from the PCI-E slot. That's why I chose the 7750.

The 7770 is 30% more powerful, but it requires up to 80W. Also it says it needs a power connector. I decided not to spend even more money on a new PS. My electricity bill is already too high. Plus the 7770 requires two slots for the metal bracket. I could modify the bracket and case to make things fit, but it would be messy.

I play games at 1024 x 768 or 1280 x 960. The 7750 is claimed to struggle at resolutions like 1920 on games like the latest Battlefield or Call of Duty. But I don't play those games. I turn off Anti-Aliasing and Anistropic filtering. I can't see any point in these functions at higher resolutions.

I used GPU Caps Viewer from
I tried the GL 2.1 Furry Cube benchmark to max out the card. The GPU Utilisation is 99%. The card temp goes up to 73C with the fan at 50% speed. Fan noise was quiet. Power drain of the computer is only 144W. The average FPS is 110 in windowed display. This is way above the 30-50 fps I expect. When playing games, the temp doesn't seems to go above 60C.

For the 3DMark06 GPU test, it manages SM3.0 Score of 7009 compared to the GMA 4500 score of 475, 29 x faster.

For a low power, low profile card, the 7750 is good. It works fine with less than 300 W power supplies.

An alternative is the Zotac GTX 650:
But I can't get it in my country.