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Odd PCIe slot status reporting when bifurcating

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ZoranC
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2020/05/24 18:13:08 (permalink)
I have Asus Hyper M.2 x16 V2 card that is in PE4 slot that is bifurcated through non-VROC option in 1.23 BIOS.
 
When card is populated with two drives (in its first two positions) green LED next to PE4 lights up and BIOS PCIe status shows x4 for PE4 (see first screenshot below, upper right corner).
 
First, shouldn’t that show x8, not x4 (it is two drives with x4 each)?
 
Next, if I populate card with four drives (or use two drives in 1+3 or 2+4 positions) then green LED next to both PE4 and PE3 lights up and BIOS PCIe status shows x4 for both of them (see second screenshot below).
 
I know that PE3 shares 8 lanes with PE4 if there is something in PE3 but there is nothing in PE3, card is in PE4, so shouldn’t LEDs and status of PCIe slots show that PE3 is empty and only PE4 is used?
 
P.S. While I use Asus card in this setup I have tried this with ASRock Hyper Quad M.2 card too and result was same.
#1

3 Replies Related Threads

    DEJ915
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    Re: Odd PCIe slot status reporting when bifurcating 2020/05/25 09:16:15 (permalink)
    I imagine it is just how it works since originally they did not have bifurcation support and it was added later so how it splits up links it thinks it is splitting off 8 lanes to PE3 when it is not and is splitting PE4 into PE4 and PE3 in one slot basically.
    #2
    EVGATech_LeeM
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    Re: Odd PCIe slot status reporting when bifurcating 2020/05/28 09:52:40 (permalink)
    Hi Zoran,
     
    Our MB/BIOS team more or less confirmed what DEJ915 suggested.  Due to the current GUI design, we are not able to show adapter PCIe mapping. So we can only show first device we detect on a particular slot.  Given the current workload of our team, I don't believe this is something they plan to fix anytime soon or the intermediate future.
     
     
    #3
    ZoranC
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    Re: Odd PCIe slot status reporting when bifurcating 2020/05/28 13:08:20 (permalink)
    EVGATech_LeeM
    Our MB/BIOS team more or less confirmed what DEJ915 suggested.  Due to the current GUI design, we are not able to show adapter PCIe mapping. So we can only show first device we detect on a particular slot.  Given the current workload of our team, I don't believe this is something they plan to fix anytime soon or the intermediate future.

     
    Hi Lee, Thank you again for your reply! I figured reporting being imperfect might be the case but when I come across something that seems to be off I like to ask about it so I can at least learn from it and assure I’m not doing/understanding something wrong about thing I am trying to use.
     
    So, now that we have put reporting aside, my most important thing is how will card in bifurcated PE4 behave if I put an x8 card in PE3? Will I still be able to see all four drives in PE4, plus card in PE3 will work fine, or if I want an x8 card in PE3 I can have only two drives in PE4?
     
    Also, it is unclear to me what is a purpose of “CPU attached storage” option in that part of BIOS, please?  Is it even applicable in non-VROC use? If it is applicable what is difference between “enabled” or “disabled”?
    #4
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