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Need some power supply help

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Posted · Original PosterOP

So i got a MT form factor Optiplex 3020 for free, it uses a core i5-4570 which holds up fairly well for low spec games but I recently got a GTX 1060 3gb OC edition for like 120$ on ebay and decided it was time to upgrade. Obviously the low watt psu's that dells ship with won't fit the bill, they don't even have a 6 pin PCIe connector. One small problem though, it seems that this motherboard doesn't use the now standard 24 pin power connector, instead it uses a different 8 pin power connector. I've found a EVGA 400w power supply at my local Best Buy but it's listed to have a 24 pin power connector. I've never built a computer before so I'm not to sure but does the 24 pin split (something like 16 + 8.) if it does split then would it work if I left the 16 pin out of the equation? The power supply has 2 PCIe connectors (one 6 pin and the other one 8 pin) so do they serve the same functionality, as in could I use the 8 pin PCIe instead of the 24 pin. Never done any computer building and I'm really low on money so I can't fork out for an adapter. I also have a couple Optiplex 390's that use the standard 24 pin connectors so if I just have to move to that than oh well, I'd really rather not though since they use a core i3-2100, I'm not even sure if their PCIe slots will be compatible with my gpu.

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The EVGA 400W is just a piece of shit. Just don't buy it full stop.


And Yeah, you cannot do a lot with that optilex 3020, since it doesn't have a standard motherboard layout and (more importantly), power connectors. You'll have to stick with the included PSU, or replace basically everything in the system (motherboard, case PSU, GPU, and probably add an SSD).


With the optilex 390's, have a look at the PSU and take some photos of it. I assume you've got a micro tower, and not a small form factor, or slim tower. PSUs in actual branded pre-builts are actually decent, (especially HP, DELL, ACER and Lenovo's business line of PCs).




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In terms of wattage, your 290W dell power supply would borderline run your system. But obviously it doesn't have the required PCIe 6-pin connector.


First we need to be clear on some of the basics.

A power supply takes the AC power from the grid, and converts it into different output voltages in DC. Generally, it delivers 3.3V, 5V, 12V, 5Vsb, and -12V. 

The wires are usually colour-coded, yellow = 12V, red = 5V, orange = 3.3V, blue = -12V, purple is for 5Vsb, and of course black is for ground.


A standard 24-pin connector looks like this




Your Dell computer is a bit different to the consumer-standards. It only delivers 12V and 12Vsb (standby). It also uses a proprietary motherboard connector.

Here's my attempt of a pinout diagram



It is crucial that each pin is correctly positioned.

You cannot simply split your 24-pin connector to an 8-pin one.

You cannot use a PCIe connector or CPU connector in there. Not only would it not fit, it would fry your parts.

You need to buy an adapter (24-pin, and sometimes a molex connector,  to 8-pin). They cost like $5. Or make your own, but preferably not.


The downside is there's no 12Vsb in the power supplies you buy. So the adapter uses a regular 12V. You may miss out on some standby features, (eg. some peripherals being powered while your computer is turned off).


I also advise against that EVGA 400w. It is not made to handle well with your system. Try look for a Corsair CX or CXM 450 or 550.


When trying to upgrade your GPU in a prebuilt system, not only should you be wary of PCIe connectors, but the PCIe slots are sometimes limited in the wattage they can deliver. According the technical guidebook for your system the PCIe x16 slot can deliver the full 75w. But the 3020 SF version is limited to 50W.

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