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Motherboards Micro-ATX PCIe slots

Discussion in 'Hardware' started by Corky42, 5 Feb 2019.

  1. Corky42

    Corky42 Where's walle?

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    I'll get straight to the point, is there an easy way to know what PCIe slot on a mATX motherboard lines up with what slot on a case?

    Looking at mATX motherboards the location of the x16 slots can vary not only in numbers but locations. It's my understanding mATX can accommodate 5 PCIe slots so while working out if a slot is the highest or lowest involves comparing pictures of different boards it's doable, what i can't workout is how do i know if the only x16 slot on a board lines up with slot 2, 3, or 4 on the case?

    If anyone cares about the reason for asking it's that I'm considering buying a Phenom mATX case but I'm concerned my existing 180mm long PSU is going to interfere or restrict the choice of GPU so i want the PCIe slot as high as possible while also leaving as much room as possible between the top fans and the GPU.
     
  2. adidan

    adidan Guesswork is still work

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    All my mATX pci-e x16 slots have been the top one closest to the CPU FWIW.
     
  3. Arboreal

    Arboreal Keeper of the Electric Currants

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    The I/O to PCIE spacing for slot '1' (top slot) is standard between motherboard sizes as I understand it. The rest then follow 'down' the board 4 for mATX and 7 for ATX.
    Some mATX cases will have 5 slots, to allow a 2 slot wide GPU in slot '4' (bottom slot) to fit the case.
    Most mATX motherboards will have the primary 16x slot in position '1' nearest the CPU.
    It would be unusual (but not unheard of) to have the main 16x GPU slot in position '2' - I do have a "not Mini ITX' board that has a 1x slot in position '1' and the main 16x slot in position '2' below.

    B-T recent review of AMD mATX board. You can see 16x slots in slot positions '1' and '4'.
    Most decent boards will support 2 GPUs, but the 2nd slot in position '4' may only have 4 or 8 PCIe lanes.
    My Asus B250 mATX board has 16x at the top, nothing in position '2' (usually blocked by a GPU, so potentially useless...), 1x in position '3' and a 16x length slot in position '4', but electrically only has 4 PCIe lanes.
     
    Last edited: 5 Feb 2019
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  4. adidan

    adidan Guesswork is still work

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    ^

    Yeah thinking about it all my past ATX and mATX boards main x16 pci-e slot have been the top slot.
     
  5. Corky42

    Corky42 Where's walle?

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    Appreciate the reply.

    Maybe some pictures will do a better job of explaining things.

    [​IMG]

    That board has a x1 PCIe connector in the first position and a x16 slot in what i assume is position two.

    [​IMG]

    That board has a PCIe x16 in position one and a PCIe x16 slot in what i assume is position 5 (or is it 4?).

    Edit: Also is there an easy(ish) way to know how far away from the top of the board a PCIe slot is? I know mATX is 244mm so is there a way to enter that distance into some image viewing program and have like a virtual ruler?
     
    Last edited: 5 Feb 2019
  6. Arboreal

    Arboreal Keeper of the Electric Currants

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    You're welcome, those are 2 interesting mATX boards :grin:.

    The Asrock is straightforward (IMHO), with 1x in position 1, and 16x in position 2...as you said. It's smaller than normal mATX in bothe dimensions!

    The Asus is 'full' mATX ~24.4 x 24.4cm which makes visual comparisons harder - I could put them in Photoshop and scale them in translucent layers, but life's too short :p:.
    The main GPU 16x slot is position 1, with the 1x in position 2 (should have been in position 3 to make it useable...).
    M.2 in position 3, and rough screen measuring with a ruler puts the 8x slot (16x length) in position 4. I do not believe there is space for a position 5 on mATX, only cases with an extra bottom slot for a CFX/SLI GPU to be accommodated in the bottom slot if appropriate.

    So, in both cases, you'd put the GPU in position 1, no question. HTH

    DON'T LOOK AT THE MAXIMUS XI GENE - your head will explode! :naughty: Someone shoehorned one into an NCASE M1 3 slot case!!!!
     
  7. Corky42

    Corky42 Where's walle?

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    Ah my head hurts as i got the image of the Asus board from partpicker and they list it as mATX.

    Either way i think i may have worked out where i got myself confused, when looking at boards last night i thought a PCI slot was a PCIe slot, who knew they were still a thing. :)

    I would just go with the closest slot to the CPU but without knowing if it's more than 180mm from the top (or in my case bottom) of the board I'd be limited in the length of GPU that could be used, it seems I've got two choices, either have the GPU crammed up against the intake fans or the PSU blocking the use of a GPU any longer than 240mm.
     
    Last edited: 5 Feb 2019
  8. adidan

    adidan Guesswork is still work

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    That Asus B450M Plus Gaming is actually mATX.

    The AsRock is interesting, can't say I've ever see a pci x1 above a x16 on any of my boards but then I've never had an AsRock and I've never owned all of the boards. :)
     
  9. Anfield

    Anfield Multimodder

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    There are quite a few of them (or at least used to be as it is becoming less common these days), the idea behind it being to make sure you always have at least one x1 slot available even with triple slot GPU coolers plus it stops you from impeding airflow to GPU fans by putting another card straight below it.
     
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  10. Arboreal

    Arboreal Keeper of the Electric Currants

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    If my trusty steel rule and calculator are correct, the 16x slot in the 'typical' Position 1 layout is ~165mm from the top edge of the board. I would have thought that should be enshrined in the ATX Standard for all mobo layouts mITX upwards.

    If I've read your requirements right, you need the GPU closer to the CPU, no further than 180mm from the opposite edge of the board. The Asus will be fine, the ASrock, will be less useful, as the GPU will be in a lower slot, further away from the top edge.
     
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  11. Corky42

    Corky42 Where's walle?

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    It would be the other way around as the motherboard is inverted so the slot would need to be 180mm from the top, thanks for taking that 165mm measurement as for me that's a major breakthrough, i tried digging out ATX standards, particularly for mATX, but the only thing i could find referenced ISA, PCI, and AGP slot distances, IDK if the slots have changed and the distances have remained the same.
     
  12. Arboreal

    Arboreal Keeper of the Electric Currants

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    That's interesting info, although outdated as you say.

    I think that slot positioning and spacing have remained the same since PCI, as the case slots haven't had to be changed...

    OK, so you need your main GPU in a non standard position if possible?

    As mentioned earlier, you need to be careful that lower slots are fully useable to
    give you the required bandwidth.
    An 8x slot should be fine, as I understand that it will give you ~95% of the required GPU bandwidth of a standard 16x slot.
    A 4x is still useable apparently, but the bandwidth loss will be too much for many applications :sigh:.
     
  13. Anfield

    Anfield Multimodder

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    The distances are unchanged, no matter if ISA or PCIe.

    The easy and dirty way to determine if your board has the highest PCIe slot in position 1 or 2 is simply to look at how it lines up with the RAM slots, if it looks like it will be hard to open the bottom clips that hold the RAM in place then the highest PCIe slot is in position 1, if not then its position 2.

    And looking at some pictures of the Bitfenix Phenom Matx case it is clear that Position 1 for the highest PCIe slot corresponds to the first slot on the case (as it doesn't have any extra slots above (or rather below) that).
     
  14. Corky42

    Corky42 Where's walle?

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    Yea but as i said if i used the first slot i wouldn't be able to use a GPU any longer than 140/150mm, in an ideal world I'd want to use what used to be the shared PCI/ISA position but there aren't any boards that have a x16 slot in that location so it's either use short GPU in a slot closets to the CPU or a normal length one that's only 10-20mm away from the intake fans.

    This YouTube video will probably do a better job of explaining things than my rather pathetic attempts. :)
    (Skip to 7:20)


    If someone can translate where the 3rd and 4th slots on 'a' motherboard are then you're doing better than me because all the mATX boards I've looked at have at most two x16 slots. :confused:

    I'm starting to think I'd be better of stumping up an extra £70 for the larger Jonsbo UMX4.
     
    Last edited: 5 Feb 2019
  15. Anfield

    Anfield Multimodder

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    I'll try some pictures:

    pci1.jpg pci2.jpg pci3.jpg

    And you are trying to avoid 1 + 2 due to conflicts with the PSU as well as 4 + 5 due to fans.

    So from what I understand the real issue will be finding a board that has a fully functional pcie slot at 3 that can actually be used for a GPU.

    I'll see if I can find some, but it might be easier to consider a different case that has "normal" PSU mounting tbh.[​IMG]
     
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  16. Corky42

    Corky42 Where's walle?

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    I wouldn't bother wasting your time, I've looked at all the mATX AM4 board and none of them have x16 slot in what would be the ideal position, in the last picture you kindly posted it would be 3.

    With all you're inputs I've come to the conclusion i was hoping, being stupid, in thinking what you've labeled as 1, 2, 3, 4 in those pictures may have been different, but there not. :(

    FWIW i didn't really want a 'normal' PSU mount as not only was i looking for a smaller case but as my PSU is passive up to 250W i was thinking having it in the front would help block some noise when idle.
     
    Last edited: 5 Feb 2019
  17. Anfield

    Anfield Multimodder

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    Yep, on the AMD front it was a waste of time.
    The only one is x399.

    On the Intel side there are a handful (mostly from MSI), but switching CPU over that issue seems a bit silly.
     
  18. Corky42

    Corky42 Where's walle?

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    It does seem that way, although at least you lot sorted out my muddled thinking, thanks for that as i was getting in a right muddle. :)

    I've decided to wait until R3 is released in the hope that a refresh from board vendors may see them place a x16 PCIe slot in that third position, if not I'll go with the second choice case, with any luck my savings will still be worth something in 4-5 months.
     
  19. bawjaws

    bawjaws Multimodder

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    You could always use a PCIE riser to shift the GPU down a slot or two.
     
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  20. Corky42

    Corky42 Where's walle?

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    I'd not thought of that, I'll have to do some research to work out if the GPU could be mounted in a sensible way.
     
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