max001

macrumors newbie
Original poster
Feb 13, 2017
17
0
Say for instance I decide to put a triple slot height graphics card in my 2009 Mac Pro, the second 16x slot would be blocked. Could I use a 3m PCI-E extension cable to make use of the second 16x slot? I appreciate any PCI-E device wouldn't have a 'secure slot' but it could be secured in the case by other means.

Basically right now i have GTX 770 4gb in my mac and 5770. GTX is powered by external 500w power supply my idea is to get 3m PCIe x16 riser cable and connect another 770 that would be attache outside via another power supply. I see people doing this in PC and it works i wonder i it will work with mac

Here is the cable i will use
https://www.digikey.com/product-detail/en/3m/8KC3-0726-0500/3M12026-ND/3641403

Thanks
 

h9826790

macrumors P6
Apr 3, 2014
15,267
7,559
Hong Kong
It's possible, at least one guy here reported successfully doing that. However, also at least another member reported that even he get the low profile cable, still can't fit that into the slot (blocked by the GPU heatsink). So, I think it really depends on your graphic card and cable.
 
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William_si

macrumors regular
Apr 4, 2016
188
55
Croatia
Depends on cable, i did this on slot 3 at some time with x4 for a pcie ssd and a GPU each in 1 and 2.

A 270X was fine in height, some Asus 280X was not.

The 3m cables are much better and for x16 absolutely better than the ebay stuff i had for x4.

Pics:
http://m.imgur.com/a/81NVk
 

William_si

macrumors regular
Apr 4, 2016
188
55
Croatia
There are a bunch, some by higher cooler covering half a slot and some as design due to TDP (eg. 390X2 variants).
 

h9826790

macrumors P6
Apr 3, 2014
15,267
7,559
Hong Kong
This is from Nvidia website

Screen Shot 2017-02-15 at 14.15.37.jpg


So, obviously, the card in this way.
Screen Shot 2017-02-15 at 14.14.38.jpg
 

esatamacmodular

macrumors member
Nov 27, 2014
82
33
I thought it was better to get risers with a capacitor and molex power on it... or is that only for eGPU? In any case, where is a good place to get pci-e 2.0 16x riser cables? or is 3m the only way to go?

...I'm looking to make a thinner desktop case and the GPU is sticking out. I thought a riser cable would help me move the card to a more suitable position.
 

Dr. Stealth

macrumors 6502a
Sep 14, 2004
812
724
SoCal-Surf City USA
You can get very powerful 2-Slot wide cards. I'm running two factory overclocked EVGA 1080 TI FTW3's that are two slots wide. I would avoid any card over the two slot width. They are cheaper to manufacture because they don't involve as much engineering. It's the easy way out for card manufactures but puts the burden on you to make them fit.
 

William_si

macrumors regular
Apr 4, 2016
188
55
Croatia
I present you the ASUS DCII 6950. Old and by now useless but 3 full slots. The comment above me is also not true; in some configurations 3 slot absolutely makes sense - See the Titan Z fiasco which would have been easily avoided this way or by liquid. Or the extreme high TDP 48xx AMD variants. Or, yes, in fact, the 7970 Ghz edition which even as Rev2 R9 270X will *easily* cross into 90C with a normal dual slot 2 fan config (eg. XFX, Sapphire), only a 3 fan config or 3 slot deeper config can hold them lower (eg. the ToxiC variants up to the 390X).

I also now use a Thermaltake riser to external which seems to work perfectly fine, to a M.2 splitter external, to an RX 480 and an RX 460 plus a 10G Myricom adapter.

Second thermaltake riser arrives tomorrow and splits slot 4 into 4x x1 for USB 3, SATA RAID and few other things.
 

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Synchro3

macrumors 68000
Jan 12, 2014
1,983
841
I present you the ASUS DCII 6950. Old and by now useless but 3 full slots. The comment above me is also not true; in some configurations 3 slot absolutely makes sense - See the Titan Z fiasco which would have been easily avoided this way or by liquid. Or the extreme high TDP 48xx AMD variants. Or, yes, in fact, the 7970 Ghz edition which even as Rev2 R9 270X will *easily* cross into 90C with a normal dual slot 2 fan config (eg. XFX, Sapphire), only a 3 fan config or 3 slot deeper config can hold them lower (eg. the ToxiC variants up to the 390X).

I also now use a Thermaltake riser to external which seems to work perfectly fine, to a M.2 splitter external, to an RX 480 and an RX 460 plus a 10G Myricom adapter.

Second thermaltake riser arrives tomorrow and splits slot 4 into 4x x1 for USB 3, SATA RAID and few other things.

Which adapter are you using to connect to PCI-E in the Mac Pro?
 

William_si

macrumors regular
Apr 4, 2016
188
55
Croatia
https://geizhals.eu/thermaltake-premium-pcie-x16-riser-cable-600mm-ac-050-co1otn-c1-a1646734.html

Available as 30, 60 and 100cm - not cheap but still WAY below what eg. 3M offers on the 'Pro' side, or the external OCULink/similar solutions. I trial this next though, components become cheap these days and external SAS is a nice standard for wiring, or at least better than bulky PCIe extenders as this + specifically designed/shielded to be routed external/bundled with other cables/etc.
 

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