Anyone ever play around with adding external GPU's to your laptop via the mini-PCIE?

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Profile Jason Roner

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Message 1889782 - Posted: 14 Sep 2017, 19:13:43 UTC
Last modified: 14 Sep 2017, 19:14:07 UTC

Had some ideas and went searching eBay and found this:

I have a Dell M4500 laptop that has two unused internal mini-PCIE slots. I could technically use them to hook up two external GPU's to crunch SETI with. Just wondering if anyone's tried this already and how did it result?

My M4500's nvidia chip is a Quadro FX1800 and not so great since it is stuck using driver 342.
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Message 1889865 - Posted: 15 Sep 2017, 2:31:28 UTC

Not all mPCIe ports will work with this kind of adapter. Having these work with standard desktop MBs and a GPU seems to be about 50/50.
For $8 it is defiantly worth a shot to see if it works.
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Profile Richard Hagen

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Message 1889892 - Posted: 15 Sep 2017, 9:44:45 UTC - in response to Message 1889782.  

I have a some similar PCIe connectors for an external graphics card, but for a regular PC as opposed to a laptop. I have some concerns about the power supplied to the board for the video card.

A couple of things to check would be that the SATA specification calls for three +12V pins on one end of the connector. The pins have to be rated for a 1.5 amp minimum, but that is only 18 Watts per pin at 12V, if not all pins are connected it could be less on some inexpensive aftermarket parts as it seems a few do not connect the +12V precharge pin. Even with three +12V pins with the amperage split evenly, that is only 54 Watts. I suspect that you can probably get away with a bit more current before it melts down in real world conditions, but if the voltage to the card drops across the supply lines I would expect erratic results.
SATA specs are outlined here:

Now the 6 pin PCIe connector on the other end is supposed to be rated at 25 Watts or just over 2 amps per pin.
A source for the pinout and power specs is here:
The specification calls for there to be pins, connected to the two yellow wires, of +12V, although I have seen some with a connected third +12V wire in the not connected pin of the specification. If only two of the yellow +12V connectors are connected that would make the max about 50 Watts. If three of the pins are connected to +12V on BOTH the board connection and the cable then that would raise to 75 Watts. The kit your referenced appears to only have two +12V yellow wires. For 8 pin PCIe power connectors, the same amps per pin applies but you have three pins minimum, or 75 Watts.

So in short, it seems to me that there is a mis-match between the available power from the SATA end and the PCIE end. Depending upon the graphics card you employ, I am thinking you could easily exceed the power specification of the SATA end.

For example the GEForce GTX 980 Ti information linked through here indicates a power consumption of up to 250 Watts: The card I looked at has two 8 pin power plugs. If you were drawing 75 watts per PCIE connector you could pull in 150 Watts, through those connectors if properly wired. That would leave 75 watts to be pulled through that SATA power connector in your kit and/or the USB type cable.

There is that additional connection, the USB cable used between the two cards in your kit but I do not know the specifications for that in this application or if any of the lines are used to transfer power from the laptops PCIE rail to the rail on the board that the graphics card is plugged into it or if it is all data traffic.

For me, with a laptop, I would probably obtain an external +12V supply with the ability to put out the total wattage of the card and tie it into the board PCIE power and the cards PCIE connectors and placing the ground in common with the laptops for reference. I suspect that power problems may cause these kits as supplied to not work with many cards on the market.

Take all of this as just my two cents worth and double check my figures, as I have not rigged up mine yet either, but I would make sure that I have enough available for the card for it to operate, especially in such an intensive manner as this application.

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Message boards : Number crunching : Anyone ever play around with adding external GPU's to your laptop via the mini-PCIE?

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