Designing the MAGIC power cable SATA – GPU

Discussion in 'Mac Pro' started by Pentaxer, Mar 16, 2019.

?

Which variant is the best – the short one or the long?

  1. The short (additional 6 pin extender is needed)

    25.0%
  2. The long

    75.0%
  1. Pentaxer, Mar 16, 2019
    Last edited: Mar 16, 2019

    Pentaxer macrumors member

    Pentaxer

    Joined:
    Oct 25, 2018
    Location:
    Russia
    #1
    Greetings!
    Need help in designing of useful item for MacProOwners – efficient power cable for GPU.

    Short reading
    I am designing the MAGIC cable to power GPU from SATA effectively. Need help. Anybody will be able to buy it from the workshop directly.

    Long reading
    High performance GPUs need a lot of power. PCIE and onboard dual 6 pins power is not enough. We make PIXLAS mod or use SATA power. Let’s speak on SATA to GPU cables.
    I, for example, use the following scheme: SATA –> short SATA to 6 pin cable –> 6 pin extender (in my case even 2 short extenders). It is not optimal because:
    1) power goes from motherboard to DVD-bay and then returns back to GPU. In my case the summary length of cables is about 1,1 m! There is energy lose;
    2) it is VERY hard to find a good «SATA-power – 6 pin» cable. For example: every 6 pin extender can provide 75 watts, but «SATA-power – 6 pin» cable - only 30 watts (several of them had been tested; maybe you can find a better one);
    3) it is not simple to insert in MacPro additional cables from DVD-bay to GPU;
    4) it is ugly (on MacPro background).

    The idea
    MacPro's motherboard has 4 pin connector (see picture 1 below) to power DVDs. Let's make MAGIC cable to directly power GPU from that connector. I have communicated with several Chinese workshops – they are ready to make it for us and then sell it to everybody. But to start production we must: make a scheme, order 20+ items. The estimate price is 10$ - depends on materials and etc.

    The design
    I have drawn 2 variants of MAGIC cable (picture 2 below; the scheme in PowerPoint for editing).

    The questions
    1) Which variant is the best – the short one or the long one?
    2) What are the official names of connectors?
    3) What length of "appendix" should be used in the long variant?
    4) What pinout must be used?

    Pictures:

    MB.jpg

    MC.jpg
     
  2. Macschrauber macrumors 6502

    Macschrauber

    Joined:
    Dec 27, 2015
    Location:
    Germany
    #2
    Question 7: can this power port deliver stable 75W without damage ?
     
  3. Pentaxer thread starter macrumors member

    Pentaxer

    Joined:
    Oct 25, 2018
    Location:
    Russia
    #3
    The result of additional investigation

    1. The optimal "appendix" length is 45-50 cm. It is >2x times shorter than summary cables length without MAGIC cable.

    2. 6 pin connector in "long variant" is better to change to 6+2 pin connector.

    3. Highly likely (1) and (3) connectors belong to that series.

    The right question is HOW MUCH power this connector can provide. I'll be happy if it is 40+ watts. It will be enough for many GPU like 7970, 280x, RX 580 Nitro+ and other OC cards such as RX 56.
    A few thoughts:
    4.1. Apple makes this connector to power 2x DVD. The upper power limit of each DVD writer consumption is 30 watts - i.e. 60 watts in summary.
    4.2. The connectors rated for 6.5A. 6.5 x 12 = 78 watts.
    4.3. SATA power connectors are rated for 4.5A. 4.5 x 12 = 54 watts
    So we may expect for 50+ watts and believe for 50-75 watts.
     
  4. Macschrauber macrumors 6502

    Macschrauber

    Joined:
    Dec 27, 2015
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    Germany
    #4
    I would absolutley NOT make a 6 plus 2 cable. So you are not responsible for overloading this power port.
     
  5. Pentaxer thread starter macrumors member

    Pentaxer

    Joined:
    Oct 25, 2018
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    Russia
    #5
    I heard about several cards that don’t work when dual 8 pin connectors are powered with 8 and 6 pin cables. Even if they don’t need so many power.

    Or such situation is exception?
     
  6. Macschrauber macrumors 6502

    Macschrauber

    Joined:
    Dec 27, 2015
    Location:
    Germany
    #6
    If the user adds a 6 pin to 8 pin adapter its his own fault. Yes, thats an exception.

    I like the idea of the ODD power plug adapter. For 6 Pin.

    8 Pin should be taken from the "standard" Double Mini PCI Power to single 8 Pin cables. Those are on the market. Sold in eBay and Amazon.
     
  7. Pentaxer thread starter macrumors member

    Pentaxer

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    Russia
    #7
    Agree with you.
     
  8. Pentaxer thread starter macrumors member

    Pentaxer

    Joined:
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    #8
    Next part of investigation:

    1. Now we know the pinout of motherboard’s connector (link).

    2. Going to use 4.5A cables. It provides 50+ watts and prevents connector from being burned.

    3. More detailed scheme of the «long variant» is attached.


    And i can’t identify connectors (1) and (2) :(



    Magic 2.jpg
     
  9. zedex, Mar 18, 2019
    Last edited: Mar 20, 2019

    zedex macrumors member

    zedex

    Joined:
    Oct 21, 2018
    Location:
    Perth, WA
    #9
    As to your original proposal/pitch - I think it's an AWESOME idea and I'd put my hand up to take 3 - 5 units if you "greenlight" this initiative.

    Separately, but still COMPLETELY ON TOPIC..... I invented my own solution that I have tested and verified working!
    I've attached an image for further scrutiny by those MR members that are "electrical engineering types" - I need to know if it was a beautiful accident OR a dangerous and deeply flawed electrical assembly that would be dumb to implement permanently.

    Dual SATA Power TO 6-PIN PCIe WEB.JPG
    [FURTHER CONTEXT / BACKGROUND] I'm just a technically minded experimenter and all I can say is that this solution worked perfectly when I 'invented' it to power an RX 480 that was shipped to me without any PCIe power connectors (and I didn't have and mini-PCIe connectors lying around).

    When I put this together my rudimentary assumption was that I was drawing 2x SATA PORT POWER (i.e. 2x 40W = 80W) and re-routing it in to the one 6-PIN PCIe connector. Anyway - looking forward to the feedback :)

    QUICK EDIT -- TEXT ON THE DIAGRAM THAT READS "(1ST) SATA POWER 15-PIN cable [LIKE THIS] plugs in to Drive Bay 2" should read "(1ST) SATA POWER 15-PIN cable [LIKE THIS] plugs in to Drive Bay 1"
     
  10. Pressure macrumors 68040

    Pressure

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    Location:
    Denmark
    #10
    It's just a normal dual row 4-pin molex connector.
     
  11. Pentaxer thread starter macrumors member

    Pentaxer

    Joined:
    Oct 25, 2018
    Location:
    Russia
    #11
    Thanks!
    Let's make the idea come true.

    Good work!
    I am also using nearly the same solution now. But it is not optimal (see the first post).


    It is a bit smaller, looks like "mini-fit" or "nano-fit". But i am not sure.
    Going to disassembly my cMP and measure it.
     
  12. Pentaxer thread starter macrumors member

    Pentaxer

    Joined:
    Oct 25, 2018
    Location:
    Russia
    #12
    The news.

    1. Highly likely the "unknown" connectors are from MOLEX "micro-fit" series. Have just ordered one to test on my cMP.

    2. The information from the workshop: the optimal L1 length is 5 cm - it can be done by machines. The shorter one require "hand made" technique, the price will be much higher. I don't see any probles in 5 cm lenght.

    Stay tuned!
     
  13. Pentaxer, Mar 25, 2019
    Last edited: Mar 25, 2019

    Pentaxer thread starter macrumors member

    Pentaxer

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    #13
    The news. Part III.

    1. Confirmed! The unknown connectors are from Molex Micro-Fit 3.0 Connector System.

    2. The cables length is refined.

    3. Going to ordered the first prototype in the workshop.

    Magic 3.jpg
     
  14. Bynsms macrumors newbie

    Joined:
    Apr 8, 2019
    #14
    Any results? When can we buy one and from where?
     
  15. Pentaxer thread starter macrumors member

    Pentaxer

    Joined:
    Oct 25, 2018
    Location:
    Russia
    #15
    There is no good news.
    The workshops are not interested in making several items. They are ready to produce 100+ to sell at once.

    Several items need to be done by hands (with no machines) - it will be very expensive (~25$ for one item).
     
  16. Bynsms macrumors newbie

    Joined:
    Apr 8, 2019
    #16
    So make a poll about it. Let the people decide if the price is worth it for them.
     
  17. Pentaxer thread starter macrumors member

    Pentaxer

    Joined:
    Oct 25, 2018
    Location:
    Russia
    #17
    PIXLAS or PSU mods can be done for this price.
    I don’t think that it’s a good idea.
     

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