MP 1,1-5,1 MacPro 4,1 / 5,1 Adequate Wattage / Wiring: 980 Ti or 1080 Ti GPU

[TrumanLA]

SOLVED via 'Pisla's Mod"

It doesn't appear as difficult as it looked at first glance:

It consists of using simple taps on 8 long wires, which are routed from the DVD area through the HDD shelf, to the GPU. I'll post any extra details or pictures after I do it ... as I'm sure I"ll find areas in which the phrasing wasn't to my liking ... (personal preference). I'll try to clarify any ambiguities I run in to with supplemental info, here.







ORIGINAL POST, BEFORE DECIDING WHAT TO USE:

Are the 2x SATA Power from ODD connectors the same channel..?
Or are there actually 2 independent power lines to draw off..?
I need two distinct SATA power 'channels' ...

Previously, it ran perfectly off the
• 2x mini 6pin PCI
• 2x 15p SATA from the 2 unused HDD slots (unless one came loose)



What I need:
Adequate wattage & clean wiring for GPUs with the power-draw of a 980 Ti or 1080 Ti that's relatively inexpensive, robust (as in, can withstand retards like the USPS or UPS doing "drop tests" for me) ... looks professional & clean ... to the point it's doesn't intimidate or make a customer think: "Merde. I can't put this GT120 in; I have no idea what the hell this guy was thinking to wire this. I'm screwed."


Adequate Wattage:
Need to power: nVidia 980 Ti -- 2x 8p PCI power inputs
Previously source: 2x SATA 15p power (unused HDD slots)
Intended source: 2x SATA 15p power (both ODD 15p SATA)
The 2 optical (DVD) drives stem off of one large cable, so I don't know what it's comprised of...

 

[mikas]

I'm not quite sure if I understood all your intensions, but personally I would not let the GPU draw 150 watts from 2x SATA power source. Though not asked, I just had to let you know this.

Still, I do know there is a 4-pin connector on the motherboard, which is designed to feed power to two potential optical bay SATA devices. I use a spare optical cable myself to feed power to 6-pin connector of my Vega 56 (card is set to low bios mode to lessen the power draw dramatically).

What I don't know is wheather there are actually 12V feed only, or is there 5V too with that connector. If there are both 5V and 12V feed to the ODD bay, all the amperage is pulled from, and will stream through only one pair of pins to both of those SATA power connectors.

With this optical cable and another 2x sata power to PCIe power (6-pin or 8-pin) you can have a more straigforward feed to the GPU.

For this 150W is way too much though. You will burn something eventually.
1x SATA power is specced at max 54W, so theoretically you would calculate it like 2x54=108W max. I would not want to draw that much continuously from there.

You can use the existing ODD cable, but will have to disassemle the Mac to get it out. Or you could buy one from e-sellers. I believe I bought a couple of those cables from thebookyard if I remember it right. That way I did not have to tear apart the Mac Pro. Just plug out the ODD cable and leave there. Plug in the new one and route according to your needs.

Please see pics.

 

[TrumanLA]

Actually, yes, those SATA (whether Molex or 15p) carry 5v and 12v, because that's what hard drives need.

2.5" drives need 5v and
3.5" drives need 12v ...

(There's also 3.3v, ... but that I don't know 'why' exactly: The 5v and 12v however are compulsory for HDDs)

We're talking about the same thing. ODD is the Optical Disk Drive ...

I'm just trying to figure out if those two SATA connections on the large cable in the ODD area are each their own channel or if tapping off both of them is 'redundant' ...


75w -- PCI slot itself
75w -- (x2) Each 6pin mini PCIe Power near the GPU
75w -- (x2) Is what I believe 4pin Molex or SATA 15p...

Should provide 375 watts total, again, IF there are 2 channels. Even though they supposedly only draw 250-300, I also believe they peak to higher draws...

Thank you very very much for your attempt to decode my gibberish ... and even more so for the in-depth reply.

 

[tsialex]

Actually, yes, those SATA (whether Molex or 15p) carry 5v and 12v, because that's what hard drives need.

2.5" drives need 5v and
3.5" drives need 12v ...

(There's also 3.3v, ... but that I don't know 'why' exactly: The 5v and 12v however are compulsory for HDDs)

We're talking about the same thing. ODD is the Optical Disk Drive ...

I'm just trying to figure out if those two SATA connections on the large cable in the ODD area are each their own channel or if tapping off both of them is 'redundant' ...


75w -- PCI slot itself
75w -- (x2) Each 6pin mini PCIe Power near the GPU
75w -- (x2) Is what I believe 4pin Molex or SATA 15p...

Should provide 375 watts total, again, IF there are 2 channels. Even though they supposedly only draw 250-300, I also believe they peak to higher draws...

Thank you very very much for your attempt to decode my gibberish ... and even more so for the in-depth reply.

While the PCIe slot can provide up to 75W to the GPU, most cards use around 40W or less.

The only high end recent card that fully use the PCIe slot power is the RX 480 reference model and this caused a lot of problems when the RX 480 was released, with PCIe slots being burned. All GPUs since then use a lot less power from the PCIe slot and are designed to be feed from the PCIe auxiliary power connectors.

 

[TrumanLA]

While the PCIe slot can provide up to 75W to the GPU, most cards use around 40W or less.

Good info, I'll calculate assuming 40w from the slot itself ...

Do you happen to know if those two SATA ports for the 2 potential ODDs in the MacPro are each an independent channel..? As in, do they provide 150w combined..? Or are they 1 channel split in two.. and only worth 75w..?


In fact, will my over all plan work:

40w -- From the PCIe slot
75w -- 2x PCIe mini 6 pin power ports...
75w -- 2x from the 2x ODD SATA connections by the ODD ... ?

~340 watts ...? Or is this wrong...?


Thanks


PS: Just remembered you; you're who first provided the info re: MacPro 5,1 and the new EFI which supports booting from NVMe SSD drives, yeah...?

 

[tsialex]

SATA spec defines up to 54W for a SATA power connector. I wouldn't expect to double it using both ODD SATA connectors, since both are connected to the same power lines.

Look at a Pixla's mod, the way you are doing it will certainly cause damage to the power lines of the backplane.

 

[TrumanLA]

SATA spec defines up to 54W for SATA power connector. I wouldn't expect to double it using both ODD SATA connectors, since both are connected to the same power lines.Look at a Pixla's mod, the way you are doing it will certainly cause damage to the power lines of the backplane.

"Pixla's mod" LOOKS liked like more of a PITA than it actually is upon careful examination. After the first one it'll probably seem easy.

Anyway, again, thank you for the good advice and pushing me over the edge. I was going to argue against it, but, it'd just be the 'inertia' of laziness. You're right. Again.



"...damaging the backplane" sounds tenuous, politely.
We've sold 100s of Mac Pros... 50+ % with 250w+ GPUs that required gerry-rigging power. Employees prepped half... but I've done dozens of 980/1080 Ti. I've seen a few weird issues but can't recall [one case] that seemed caused by a 250w GPU culprit. GPUs that died? Sure. And, I'm sure it's POSSIBLE...just can't be too common.

 

[mikas]

Yes, of course there's 5V too, how stupid of me. You can put hard drives in there. No 3,3V though as in spec, because as you can see from my picture, the cable that feeds the power to the ODD compartment has got only 4 pins in it.

And doesn't that mean all of the (12V) current comes through "one channel" aka two pins (and traces) only.

I pull max 32W from there, and would not want to draw much more than that. So me too am gonna order some taps for Pixlas mod really soon.

 

[TrumanLA]

Yes, of course there's 5V too, how stupid of me. You can put hard drives in there. No 3,3V though as in spec, because as you can see from my picture, the cable that feeds the power to the ODD compartment has got only 4 pins in it.

And doesn't that mean all of the (12V) current comes through "one channel" aka two pins (and traces) only.

I pull max 32W from there, and would not want to draw much more than that. So me too am gonna order some taps for Pixlas mod really soon.

Yup; I was going off memory and just looked at it today ... and once I did it was pretty obvious. I agree with you.

Maybe we should conspire about our process together in PM or email...?


If so: TrumanHW@gmail.com


Thanks