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PCIe Standards

Discussion in 'Graphics Cards' started by Desert Eagle, Jul 6, 2012.

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  1. Desert Eagle

    Desert Eagle New Member

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    I have a ? that I hope someone can answer. Why is the PCIe set up like it is? A 6 pin connector has three 12 volt wires and three grounds and a 8 pin has three 12 volt wires and five grounds. It's just two additional grounds? I don't get it. Why not have one 12 volt wire and one ground. Saves production cost. Reduces clutter. In addition to this I have had to splice PCIe cables on one rig and I am amiss at the puny aluminum wires that the three 12 volt wires carry. I wouldn't trust a nightlite to carry that load. Why don't they just use one quality power wire and one quality ground? Why complicate things?
  2. MightyMission

    MightyMission

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    I'd imagine it's for power phases
  3. Steevo

    Steevo

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    Many cables make the load lite.

    More cables means the chance of a break in one wire and massive failure of the motherboard due to the high load shift is decreased to an acceptable degree.
    10 Million points folded for TPU
  4. 1freedude

    1freedude

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    Its actually about the contact on the connector. The individual wire can carry the load, the connection can't.
  5. Desert Eagle

    Desert Eagle New Member

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    Thank you for your varied responses and I'm sure this strikes some of you as a simple question but I enquire further because I want to know what you know. I can plug an appliance into a wall receptacle and it has a power wire and a ground wire. No need for 3 power wires and 5 ground wires.

    "More cables means the chance of a break in one wire and massive failure of the motherboard due to the high load shift is decreased to an acceptable degree."

    But wouldn't one appropriate sized wire be better than 3 flimsy wires? I don't understand what you mean by a high load shift.

    "Its actually about the contact on the connector. The individual wire can carry the load, the connection can't."

    This is puzzling as a high end GPU can use 100's of watts on a small chip. The connections there are solid, even microscopic if you want to get down to the basic architecture.
  6. 1freedude

    1freedude

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    Sure, but when was the last time you needed a heatsink on your connection?

    As a side note...I'm welding right now on a constant current machine. The wire, or lead, going to the torch is roughly 8 gauge, and can handle 250 amps, varying in voltage from 8 to 24 DC. That's a a lot. The connection is screwed together at each junction...and it's water cooled. If it were not water cooled, the wire goes up to 1/2 inch diameter and the connections are different.
  7. Desert Eagle

    Desert Eagle New Member

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    As a side note...I'm welding right now on a constant current machine. The wire, or lead, going to the torch is roughly 8 gauge, and can handle 250 amps, varying in voltage from 8 to 24 DC. That's a a lot. The connection is screwed together at each junction...and it's water cooled. If it were not water cooled, the wire goes up to 1/2 inch diameter and the connections are different.

    What is this machine? What is it's purpose?

    As a side note to you 1freedude...be careful with that amperage even at such low voltage. We don't want to lose you pal.
  8. 1freedude

    1freedude

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    TIG welding. That's what I do.
  9. Desert Eagle

    Desert Eagle New Member

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    Well done. Thank you for your input.

    Can we get back to my ? if no one is too busy welding Chevy transaxles to their damn foreheads?
  10. Desert Eagle

    Desert Eagle New Member

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    I guess not but that is probably because I'm a stupid dick-head.

    Well, anyway, thanks for your answers, albeit weak as they were.

    Fare well.
  11. lilhasselhoffer

    lilhasselhoffer

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    I have not seen someone miss the point on so many different levels at once in quite a while.

    1) There is no pci-e power cable. You could either mean the pci-e bus connector, or the extra power connectors (6 and 8 pins) that are currently exclusively meant for graphics cards. Assuming the latter, why is a maximum of 8 pins an issue?

    2) AC=/DC. Comparing a wall outlet on AC, to a PSU that runs several different DC outputs, is foolhardy at best.

    3) Resistance is inherent in all wires (unless they are a superconductor). This means that too much amperage passing through it will melt it. The size of wires is set by connection standards, so that you can actually hook up a PC to other components.

    4) Whining without understanding fail. This is my last point, but it will take time.
    Imagine you are building three PCs right now. One is an HTPC, the other is a gaming rig, and finally a workstation for graphics rendering. Lets say you use one motherboard manufacturer, and three different PSU manufacturers. You can now hook-up extra leads to the workstation to provide extra power, but still have the same basic connections for an HTPC. That's for a good reason.

    Now imagine if there were no standards. Motherboard manufacturer x, the one you purchased from, has three different boards, with power requirements that vary dramatically. You need to choose a PSU that not only meets your requirements on voltage and amperage, but meets connector size requirements. Because each board varies substantially, the amount of PSUs you can choose from per build is two. Those two PSUs can have an artificially inflated price, because there is no competition.

    For those too young to remember, this is how Dell used to work. Proprietary connectors and standards made it impossible to service a PC without Dell parts, creating a very lucrative mark-up in pricing for Dell.



    So, no. The idea of bigger connectors is stupid, because standards exist for a reason. If you want to change the standards you are welcome, but moaning isn't going to do it.




    PS:
    Chips have millions of gates. The small size is an afterthought, because the cross-sectional area is huge, which is what allows large amperages (and therefore large amounts of power) to flow.
    Desert Eagle says thanks.
  12. CaptainFailcon New Member

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    Op does not seem to understand how Ic's and voltage stepdown works
    if you take 12v and step it down to say 1v you have a whole lotta amperage there and little need to draw much amperage though the connectors you do how ever require more grounds
    input voltage of 12 Steped down to 1.2 with 300WAT available to the gpu though the 8Pin connecters would be 250AMPs
    most gpus run less then 1.200v

    12V@300Wats is only 25AMP so if the rating for the PSU is 50AMP's On the 12V rail or if the psu is multirail with two 25AMP rails well there you have it
    Last edited: Jul 7, 2012
  13. Desert Eagle

    Desert Eagle New Member

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    I have a basic grasp of DC power. I understand that increasing the amps requires increasing the diameter of the load carrying wire because of resistance. But, let's use my car battery for example. It has one positive post and one negative post. I have one power cable and one ground cable. There's no need for 3 power cables and 5 ground cables for my 12 volt car battery.

    "if you take 12v and step it down to say 1v you have a whole lotta amperage there and little need to draw much amperage though the connectors you do how ever require more grounds"

    Yes, but that's after the fact. My ? isn't what happens after the video card receives it's power. My ? is about the transmission wires. Why not use one power wire and one ground wire?
  14. Desert Eagle

    Desert Eagle New Member

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    Well, I guess we can close the file on this one. VGA cards require 6 pin and 8 pin power cables just because. Well, that's it. PSU manufacturers can eat it. Stupid crappy aluminum wires instead of two proper copper wires.

    Stick a fork in me I'm done.

    Stupid Waste!
  15. CaptainFailcon New Member

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    because no one wants to route 10AWG wire though there cases because 18 or 20AWG is more then enough :banghead:
    because having more then one +12 input is useful for gpu's because you need to power things like the fan and the memory chips and cross-talk would be bad the 18AWG wires in my case will handle 10AMP's each all day long ... a pcie connector has 3 10+10+10 ~30
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  16. Desert Eagle

    Desert Eagle New Member

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    Oh. Well I'm sorry for being a brickhead but you and some others here know a lot more than some of us and the generally accepted rule is to piss you people off and then you will teach us what you know.

    Thanks again to all. :)
  17. newtekie1

    newtekie1 Semi-Retired Folder

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    Also, the standard for 6-pin doesn't require 3 12v wires, it only requires 2 12v wires and leaves the 3rd optional. The standard for 8-pin requires 3 12v wires.

    And yes, the smaller wires are preferable to bigger wires to allow easier cable routing, because thicker wires are generally harder to route.

    Also, when the standard was being created, multiple 12v wires also allowed the load to be split across multiple rails on weaker power supplies. Back when the standard was being created 350w power supplies were still common in mid-range machines. So splitting the load across two weaker rails was an option(though obviously not preferable).
    Crunching for Team TPU 50 Million points folded for TPU
  18. Desert Eagle

    Desert Eagle New Member

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    "And yes, the smaller wires are preferable to bigger wires to allow easier cable routing, because thicker wires are generally harder to route."

    So if I put a GTX 580 in my rig then a stupid ass 6 pin and a 8 pin power cable is "easier to route"? Am I missing something here?
  19. Desert Eagle

    Desert Eagle New Member

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    And what the hell does rails have to do with anything? A PCIe connection doesn't factor in multiple rails. Plug it in and it uses the rail its' plugged into, period.
  20. cadaveca

    cadaveca My name is Dave

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    Xtra wires are "sense" wires, that notify the hardware that it is allowed to pull the extra power an 8-pin provides, as well as notifying the PSU that it is going to provide that power. They are not exactly "ground" wires. See below:

    [​IMG]

    A single "sense" says that 6-pin is connected, and 75 W can be drawn. Two sense wires indicates 8-pin, and 150 W can be drawn. Pretty basic, actually. If the card doesn't detect dual sense on 8-pin plugs, it knows it can only pull 75W, and many cards will not boot, or make audible cues based on the availability, or lack thereof, of the right connector. OF course, this is dependant on each individual VGA.

    Actually, thats a good way to get ignored. That is NOT an accepted rule here on TPU. THat's how you get infractions, and a ban. Just sayin'. ;)

    Attached Files:

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  21. newtekie1

    newtekie1 Semi-Retired Folder

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    Yes, you are missing something. Go grab a pair of jumper cables, and try running the wires through your case. Have fun. That is why thinner cables are prefered. They bend easier, and are easier to hide.

    Go look up how rails on a power supply work. The connector doesn't factor in multiple rails, but the manufacturer of the PSU does. Having 2 12v wires means the 6-pin connector can pull from 2 different rails on the PSU.
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  22. Desert Eagle

    Desert Eagle New Member

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    "A single "sense" says that 6-pin is connected, and 75 W can be drawn. Two sense wires indicates 8-pin, and 150 W can be drawn. Pretty basic, actually. If the card doesn't detect dual sense on 8-pin plugs, it knows it can only pull 75W, and many cards will not boot, or make audible cues based on the availability, or lack thereof, of the right connector. OF course, this is dependant on each individual VGA."

    I missed that item. So the 5th or 6th wire can sense it's whereabouts? Not necessarily another stupid redundant ground wire.

    "Actually, thats a good way to get ignored. That is NOT an accepted rule here on TPU. THat's how you get infractions, and a ban. Just sayin'."

    That's the only way I know to get you people to teach me the things that I don't know.
  23. CaptainFailcon New Member

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    Not sure if trolling
    OR
    Just doesn't understand ...
    we have only explained it 8 times
    just because you don't understand it does not make it any-less correct
    the people that make these things know what they are doing and there done this way for a reason
  24. m1dg3t

    m1dg3t

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    To put it in its most simplest form; single 18awg wire can not handle the amps required to power GFX card and 10/12awg is too thick for PC users. If you want technical re-read the thread.
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  25. Desert Eagle

    Desert Eagle New Member

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    Just because your smarter than me doesn't make you correcter. I still don't understand why the graphics card can't have one power cable and one ground.

    "the people that make these things know what they are doing and there done this way for a reason."

    So we should just shut up and accept their greater wisdom? No matter that they may be idiots. Just eat it? Is that what you're telling us?

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