Where to find more detailed specs about wattage from different ports on Mid 2010 MP?

Discussion in 'Mac Pro' started by RobertSix, Feb 22, 2014.

  1. RobertSix, Feb 22, 2014
    Last edited: Feb 22, 2014

    RobertSix macrumors member

    Sep 21, 2012
    I have found http://support.apple.com/kb/sp589 and http://www.everymac.com/systems/app...pro-quad-core-2.8-mid-2010-nehalem-specs.html but still lacking the info I need.

    Specifically I'd like to know what wattage and ampage SATA provides.

    I have seen a few of these cables which turn 2 x SATA connections into an 8-PIN PCI-e power. e.g. http://eu.startech.com/Cables/Compu...s-Video-Card-Power-Cable-Adapter~SATPCIEX8ADP and therefor negating the need for a addon PSU.

    But I have also read to be careful about ampage from SATA, but I believe this comment was in reference to somebody only using 1 x SATA port for the power, not 2 like the above link.

    Anybody know more about this or where I can look?
  2. RobertSix thread starter macrumors member

    Sep 21, 2012
    I found this page detailing different power cable connections. http://www.moddiy.com/pages/Power-Supply-Connectors-&-Pinouts.html

    To the bottom of the page it has SATA and says that there are 3 lines at 12volts with a max of 4.5 amps each. Does this mean that 1 SATA can actually provide 162 watts? (3 lines of 54watts each?)
  3. olegunnar macrumors member

    Oct 29, 2013
    I'll admit to not really knowing anything, but I'm pretty sure the 3x12V lines can provide 4.5 A total, not 3 x 4.5 A. To move 162 W (and the 3 and 5 V lines, I suppose) through light wires is a lot.

    As mentioned I don't know SATA, the MAC PRO 2010 or even the cables, so take it for what it's worth. 162 W sounds like a lot to me. The page you linked to also adds the 12x4.5 to 54W in their table. I guess they would do 12x4.5x3 if that was really the case.

    EDIT: MAC PRO 2010, not 2012.


    To further my theory, there's this page from Toms hardware:

    Specifically this section:
  4. RobertSix thread starter macrumors member

    Sep 21, 2012
    Well you don't have to be an expert but it sounds like you know more than me olegunnar!

    4.5 A total does make more sense looking at the chart again.

    So how does it add up to deliver the equivalent of an 8 PIN PCIe? I guess you would definitely need to be using 2 x SATA's to achieve this 150w of an 8 PIN.

    The chart says the sata cable has:

    +3.3 volts 3 lines, 4.5 amps, 14.85 watts
    +5 volts 3 lines, 4.5 amps, 22.5 watts
    +12 volts 3 lines, 4.5 amps, 54 watts

    So I'm guessing it must combine all these watts together to get 91watts per cable. Does that sound right? 2 cables therefor able to supply 182w?

    I'm no electrician or engineer so I don't know how different volts work. Is the graphics card just going to pull juice down from one of these lines or pull them all together to get what it needs?
  5. olegunnar macrumors member

    Oct 29, 2013
    No, it doesn't work like that.

    Looking at your link to the converter cable (which I missed the first time), my guess would be that they're combining the 3 12V pins from each SATA connector into the two yellow wires going to the PCI-E connector. From doing a quick read, it seems an 8-pin PCI-E power connector has three 12V lines and five ground lines, which seems to be consistent with the image shown for the converter cable: It has two 12 V lines from the SATA connectors, one of these being shorted to the third pin; two gnd lines from the SATA connectors, with three extra shorts on the PCI-E cable.

    To sum up, I think it's a fairly safe bet that the PCI-E connector uses the 12 V lines from the SATA connectors, for a (guaranteed to be within specification) power draw of up to 108 W. Maybe the PCI-E board you consider doesn't require more power than that. Maybe your PSU can deliver more (assuming the wires are thick enough to handle it safely).

    This is all speculation on my part, though. As mentioned I don't know anything SATA or PCI-e, except for what I've just googled.
  6. RobertSix thread starter macrumors member

    Sep 21, 2012
    I see - thanks for clearing that up. It is likely I am lame at both google and interpreting the language of electrical engineers. Grateful for your help!

    My card is a 7970 which is rated at a max draw of 300w. So 75w from the PCIe slot, + 75w from the 6 pin, leaving the 150w to get from elsewhere. If the 2 can only draw 108w then I am short about 42w.

    If your interpretation is correct that it is only going to draw 2 x 54w, I wonder why many sites who sell these 2 SATA -> 8 PIN cables say it is perfect for those who don't have a place to plugin in an 8 PIN. Is it because they understand that typically the things are given a rating that is far far under the real capacity? e.g. it could be rated at 54w, but really could go twice as much?

    Just the math doesn't add up, hence why I posted here.

    I know some people here are even just plugging their 8pin straight into a 6pin with a adapter and have no issues!

    Would love to know whether it is safer using a 2 x Sata split -> 8 PIN, or doing a 8 PIN -> 6 PIN adapter. When I saw these sata splits my immediate thought was that this would share the load a bit easier then the latter.


    I can see in the specs that 300w is split across the 4 PCIe slots, but does anybody know what has been split across the 4 SATA slots?

    I understand that HD's use very little wattage, like 10w or something tiny like this for a typical drive.
  7. Robert Davies macrumors 6502

    Robert Davies

    Jul 28, 2011
    People's Republic of Wrexham
    Sorry for a quick divert, but I was on Tom's Hardware site last week looking at specs for cards comparative to a 7950.

    The interesting section, that I now cannot seem to find my way back to (d'OH!), showed several cards under many different loads, but in excess of 95% of the time (my best estimate from reading the data) the cards were nowhere near their rated power, even under some quite complex game benchmarks.

    In application use, vid editing, photo editing etc, the cards were rarely much above a third loading.

    So, I am just taking a long way around to agreeing with you. I strongly suspect that TDP ratings for cards and power supply ratings for the MP are biased generously in your favour.

    That is all - I'll get me coat…

  8. olegunnar macrumors member

    Oct 29, 2013
    I would guess (a wild guess - don't try this on account of me) that PSUs will generally deliver 75 W per SATA connector, even though the specification is less. I I were in your situation, my primary concern would be cable heat (or even melt), but that's because I have no idea about the wire thicknesses. It probably won't be a problem (but again, trust your own judgement instead of mine).

    It's probably tiring to read all my disclaimers. I just want to make sure the context of my posts are understood.
  9. RobertSix thread starter macrumors member

    Sep 21, 2012
    Appreciate the divert Robert. I suspect they are rated way under what is really possible as well.

    The disclaimers are definitely valued olegunnar! I would hate to fry something. I'm guessing all cables are not created equal either? Some brands are cutting corners? Any tips on what brands to avoid?

    If each SATA does provide 75w each, that is great news and brings it all in the range of 2 x Sata's providing just shy of 150w. Would be great to get some verification from this. If it is possible to power an 8 PIN from 2 x Sata to get that 150w, and it is safer than trying to get the juice from a 8 PIN -> 6 PIN in the motherboard, I think a lot of MP users might save themselves some cost from the need for an extra external PSU to get a more greedy GFX card.
  10. Robert Davies macrumors 6502

    Robert Davies

    Jul 28, 2011
    People's Republic of Wrexham
  11. olegunnar macrumors member

    Oct 29, 2013
    I think I was a bit unclear. I didn't mean to imply that SATA power connectors deliver precisely 75 W, but rather that I would imagine most PSUs would happily deliver more than the 54 W the specification states.

    Also, when I talk about wire thickness, I'm talking about the existing SATA wires, not the adapter cable. There's different quality of everything, and while I wouldn't buy the cheapest stuff, I don't think there's a big risk involved in an adapter cable of this kind.

    If you determine the SATA power wires to be fairly thick (they probably are), I don't think there's much to be concerned about there. If you're a belt and suspenders kind of guy (does that term exist in english?), you could always touch the cable to see if it runs hot when powering your gfx board. It shouldn't.
  12. ActionableMango macrumors G3


    Sep 21, 2010
    It looks like everyone using a 7970 is simply using the existing two PCIe power ports. As they are having experimental success for quite a long time now, that would seem to be the logical choice over trying to use SATA. It also has the merit of being much easier to wire.

    MACVIDCARDS has pointed out that not all 6pin-to-8pin adapters are equal, so if you go this route, get a proper one.
  13. RobertSix thread starter macrumors member

    Sep 21, 2012
    That is true. What I am trying to work out though is which method would serve the power with greater ease. As far as I know, these 2 x Sata -> 6 Pin or 8 Pin are a relatively new addition to the cable world so they weren't around when the pioneers were testing these more power hungry cards.

    Many people have also suggested a potential of burning of the traces on the logic board by trying to plug the 8 PIN's into the 6 PIN's via adapter. Since the SATA's look to me like they are powered via an alternative route, I figure this could balance the load some.

    Since I put in a PCIe SSD drive, I now have 3 SATA slots being wasted. I don't know the numbers yet of what is possible, but with 3 SATA's and 2 x 6 PIN's on the logic board, that might actually even be enough to power 2 GFX cards without an external PSU.

    With the nMP now having 2 x GFX cards, crossfire is clearly in the works. And perhaps on my cMP, I could still have an elegant and powerful solution for many years to come.
  14. RobertSix thread starter macrumors member

    Sep 21, 2012
    This is great. One user says there:

    That is in reference to a 2 x SATA -> 6 PIN PCIe.

    I chatted to Startech technical support yesterday and nobody could actually give me any numbers about wattage!

    I want to know also if a 2 x SATA -> 8 PIN is going to draw more than a 2 x SATA -> 6 PIN. Obviously an 8 PIN one is rated twice as much in wattage, but what is a SATA output rated for?
  15. RobertSix, Mar 19, 2014
    Last edited: Mar 19, 2014

    RobertSix thread starter macrumors member

    Sep 21, 2012
    Following up this thread I have some real world results now after trying this solution.

    I have plugged in a Sapphire 7970 Vapor X which comes with 2 x 8 Pin connectors. This is quite a power hungry card and comes already clocked at 1050/1500.

    Using a Startech 2 x Sata split -> 8 Pin, I theorised each sata could provide 4.5 amps each based on typical data I found about what is normally provided down sata power connections, giving a total 9amps or 100watts for 1 of the 8 pins. In reality, monitoring with iStat menus doing a GPU stress test each sata pulled a maximum of 2.66a, providing only a total of 45.11w from 2 combined sata's!

    3.03a (36.78w) was pulled directly from the PCIe slot.

    7.98a (96.87w) was pulled from the PCIe Slot Boost 1.

    In total drawing about 178 watts.

    The point of concern is how little those 2 Sata's pulled. That was a real surprise to me as I thought I might have found a way to safely provide ample power to a power hungry card like this without the need for external power, or without overloading the PCIe boosters.

    So far, things have been completely stable in Mac. But I believe the drivers in Osx are stifling the card and it doesn't push the potential of the card enough to create a freeze. In windows however, when I push the card, it does freeze like toes in the winter.

    I'm going to switch around some of the cables and run some more tests and see if the data remains the same.

    Below is a screen grab of the power usage while running a stress test:

    Attached Files:

  16. RobertSix thread starter macrumors member

    Sep 21, 2012
    Just wanted to see if PCIe Boost 1 was any different to #2 since I heard a users report in another thread that they had different results and it only worked when plugged into one of the connections, however on my 5'1MP both PCIe boosters are identical and pull 7.98a.
  17. WildBB macrumors member


    Mar 13, 2014

    If you want a good 6-8pin adaptor, I purchased one Amazon and it is of very high quality. Search: Manhattan 8-Inch 6-Pin PCI-E to 8-Pin PCI-E 2.0 Cable. It is a braded cable, though the images does not show.

    Also, you may be interested in a few tests I ran using a GTX680 6+8pin card on my macpro as may help your decision with choosing the best configuration to power this card.

  18. RobertSix thread starter macrumors member

    Sep 21, 2012
    Thanks for that cable recommendation.

    Looks like your MP has the same power draw from the 2 x Sata's as what I achieved.

    These 2 x Sata cables are sold as 8 pin alternatives for people who don't have a spare 8 pin on the board. This definitely doesn't seem to be the case with how the power is shared on MP Sata's. With that being said, the MP Sata connection is not standard, and I had to mod my sata cable to be able to connect. Did you do the same? The MP sata connection also has an additional set of pins, and I'm wondering if power is also provided through those.
  19. WildBB macrumors member


    Mar 13, 2014
    Yes, I had to slightly modify the cable; just cut off one of the exterior clips on each connector.

    Correct me if I am wrong, but this is how I understand the SATA power capabilities for the 12V system:

    Each SATA cable has three 12V pins that are rated at 1.5A. (12*1.5*3= 54W per cable) Two cables will provide up to 108W of 12V power which is still much less than an 8pin Molex can request (150W). This was my hesitation in using a two SATA to 8pin Molex adaptor; Did not want my card to write a check that the SATA MB connections could not cash.

    I have attached a pin breakdown.

    Attached Files:

    • SATA.JPG
      File size:
      29.9 KB
  20. WildBB macrumors member


    Mar 13, 2014
    What tests did you perform to stress the card?

    Also, the video card does not evenly pull power from each of its available locations (PCIe, 8-pin molex 1 and 8-pin molex 2). Each system on the card is assigned to pull from a specific location. If you have two 8 pin molex connections, the loaded power draw for each port is greater than 75 and less than 150W.

    I also found, as you did, that the power draw from the PCIe slot was minimal. This is again another reason why you have 2x 8pin molex to power your card and not two 6-pin molex.

    Why do you think your card locks up in Windows bootcamp? Drivers? Have you installed any hardware monitor to look at this in windows?
  21. WildBB, Mar 21, 2014
    Last edited: Mar 21, 2014

    WildBB macrumors member


    Mar 13, 2014
    Thought I would ask, what application are you using to monitor the hardware sensors on your mac. I use iStat or HWMonitor and they do not provide any power information on the hard drive bays that I can see.

    I have a Mac 3,1 which may explain the fewer sensors. Would be nice to hear if someone has ran into a chart detailing all the MacPro sensors and which models have which sensors.
  22. RobertSix thread starter macrumors member

    Sep 21, 2012
    I'm using iStat, the same as you but I can see that ours is different. Yours doesn't appear to be reporting the Sata power, but on mine I can see both Volts and Amps for all 4 drives. What version are you using? I'm still on 3.2.
  23. WildBB macrumors member


    Mar 13, 2014
    I am using 4.2, but I don't remember seeing them even on version 3 when I was using it. My thoughts are that your newer Mac Pro has more sensors than mine...
  24. RobertSix thread starter macrumors member

    Sep 21, 2012
    To test in Mac, I'm running Geek3D's GPU Test doing the stress test at 1920 x 1280.

    I have yet to find a program in Windows which will report the usage of power consumption of anything other than CPU and fan speeds. Do you know of one for windows?

    Just going on the assumption that the bottleneck is these 2 x Sata's only giving out 2.66a when running a stress test in Mac. I'm not an electrician, but my calculations (12 * 2.66 * 2 = 63.84w) mean this isn't even substituting a 6 pin's 75w. I think you could get away with using 2 x Sata's to substitute a 6 pin, even though it is under spec, but definitely not for an 8 Pin.

    A lot of assumptions here on my end because a) I don't know if Mac is even pushing the card to the limits so b) I don't know if this 2.66a is the max of what the each Sata output can provide and c) This is all new to me, I'm not using any special mac drivers for the card or flashed rom as I can't seem to work out if there is any benefit to this.

    If I had some monitoring software on the bootcamp I think it would help a lot to debug this but as it stands I'm in the dark going on guesses.
  25. electonic macrumors member

    Mar 18, 2014
    My post on Netkas.org was about the use of 2 x SATA to 1 x 6 pin.
    From specs SATA can provide up to 4.5 Amps from each port.
    So 2 SATA would give you 9 amps in theory.

    2 x SATA to 1 x 6 PIN = up to 9 amps / ca. 100 Watts.
    Never NEVER go 2 x SATA to 1 x 8 Pin.

    So running a 7970 I would go for 2 x SATA to 6 pin from Mainboard, not DVD cable and 2 x 6 pin to 8 pin from Mainboard.

    That combines to:
    75 Watt from Slot
    2 x 6 pin to 1 x 8 pin = up to 150 watts
    2 x SATA to 1 x 6 pin = up to 100 Watts (from spec for SATA).

    This is the safest configuration for running these cards from internal power.
    I would not go for heavily over clocked cards, but for 7970 cards with the regular TDP of about 250 Watts, to be on the safe side. Don't buy cards that need 2 x 8 pin!

    There have been a lot of reports of people running cards like this without issue.
    But I don't run a configuration like that and you have to make the choice, It's you risk, although from specs this configuration should work without a problem!



    My current project is dual GPU on internal Power only.
    For that I will under clock 2 x Radeon 270x to get them to TDP < 150 Watts.

    I will report on this forum if I'm successful.

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