Question Maximus Extreme Z690 with Two M.2 SSDs

XAKEP

Junior Member
Jan 24, 2015
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Quick question guys.

Looking at the planogram below, where do I put two M.2 SSDs NOT to get my 3090 GPU to go to the x8 mode.

I have Samsung 980 Pro that is PCIx4 NVME is my bootable drive and 970 Pro NVME that is PCIx3 as Programs SSD

From what I understand Boot will go to M.2_2 (CPU direct lines) and Programs will go to M.2_3 Chipset lines slot.

Is that correct?
Thanks !
m.2.jpg
 

Justinus

Platinum Member
Oct 10, 2005
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Usually this is easily answered by looking at the motherboard's block diagram, but it seems Asus omitted it from the manual for this board.

We can stil look at the platform block diagram.

1636389379752.png

It appears the CPU only offers 16x pcie 5.0 Lanes + 4x 4.0 Lanes. This would indicate the m2_1 slot rated for pcie 5.0 uses some of those 16x 5.0 Lanes, taking them from the second pcie slot which indicates that forces the board to run the primary slot at 8x instead of 16x.

I would use M2_2 for your OS/boot/fastest m.2 drive and m2_3 for your slower/data/app drive as it will likely have slightly more latency and may be slightly slower, being a chipset m.2 slot.
 
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Justinus

Platinum Member
Oct 10, 2005
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PCIe 5.0 x8 is 32GB/sec; I wouldn't worry about it personally.
If he's got a gen old graphics card, it will only run at pcie 3.0 8x. Even a current gen will only run pcie 4.0 8x. Whether there's a tangible performance hit or not is another question.

Unless he wants to run 3 m.2 ssd's, or has the need for both SSDs to be CPU connected, there's no reason to populate the M2_1 slot.
 

Spicedaddy

Platinum Member
Apr 18, 2002
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It doesn't say that M.2_1 drops the first GPU slot to 8X, just that it disables the second GPU slot. My guess would be that it does drop to 8X since the CPU only has 4X PCIE 4.0 for the SSD (M.2_2) and 16X PCIE 5.0 for the GPU.

So yeah, I'd do it like you said, boot in M.2_2 and data on M.2_3.
 
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Justinus

Platinum Member
Oct 10, 2005
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It doesn't say that M.2_1 drops the first GPU slot to 8X, just that it disables the second GPU slot. My guess would be that it does drop to 8X since the CPU only has 4X PCIE 4.0 for the SSD (M.2_2) and 16X PCIE 5.0 for the GPU.

So yeah, I'd do it like you said, boot in M.2_2 and data on M.2_3.
I skipped over a few steps of logic there, but yes. It will run the primary pcie slot at 8x.
 
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KentState

Diamond Member
Oct 19, 2001
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What's not clear to me is how the DIMM.2 slot is wired up. Those both potentially would go to the CPU and not impact the PCIE slots. Would also make it easier to maintain since you can pop the card out and not have to mess with the plate.
 

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