AM5 x670 Motherboards That Don't Drop PCIe from x16 When M.2 Populated?

Tetras said:
Which boards are you looking at?

Ryzen 7000 can technically support up to 2x PCI-E 5.0 M.2 slots from the CPU without having any impact on GPU lanes, though in reality only higher-end X670E boards use this many M.2 slots.
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Was thinking about getting this one:

www.overclockers.co.uk

Asus ROG Crosshair X670E Hero (Socket AM5) DDR5 ATX Motherboard

Order Asus ROG Crosshair X670E Hero (Socket AM5) DDR5 ATX Motherboard now online and benefit from fast delivery.
www.overclockers.co.uk www.overclockers.co.uk

But I want 4x 4tb M.2 cards, slots all populated, as well as x16 for the GPU for future proof (I have a 3090 right now).
 
Tetras said:
The reason that the Hero has this problem isn't because X670E can't use 4x M.2 slots and retain the 16 lanes. It is because the Hero tries to give you 3x PCi-E 5.0 M.2 slots, which is not possible. If you only use the onboard 2x PCIE 5.0 and 2x PCIE 4.0, then there's no impact.
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The Hero gives 2 PCIe 5.0 m.2 and 2 PCIe 4.0 m.2. The other 5.0 m.2 is the optional expansion card.

I only plan to use PCIe 4.0 m.2 cards... I don't need more than 7gbps speeds for storage.

I thought if 4 slots use 4 lanes each, that's 16 lanes used for m.2 drives... that leaves just 12 lanes left for the PCIe slots hence the drop to x8.

Unless a couple of the m.2 slots can drop to x2 lanes instead of x4 :confused:
 
Tetras said:
Ryzen 7000 CPUs have 16 PCI-E 5.0 lanes for the graphics card, 4 PCI-E 5.0 lanes for M.2 and 4 further PCI-E 5.0 lanes for whatever (including M.2, if the board maker chooses).

The X670E Hero uses all of the CPU's PCIE 5.0 lanes, with 16 lanes for the graphics and 2x4 for the M.2.

The 2x M.2 slots that are not PCIE 5.0, don't come from the CPU, but from the chipset.

The expansion card steals the lanes from the graphics card, because neither the CPU or the chipset have enough PCI-E 5.0 lanes to have 3x PCI-E 5.0 M.2 slots.
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Right, so:

x16 PCIe lanes = GFX or some lanes stolen by expansion card leaving GFX with x8 (total lanes: 16)
x4 PCIe 5.0 lanes (CPU) = 1 m.2 slot (total lanes: 20)
x4 PCIe 5.0 lanes (CPU) = 1 m.2 slot (total lanes: 24)
x4 PCIe 4.0 lanes (chipset) = 2 m.2 slots (total lanes: 28)

How can a total of x4 lanes from chipset make 2 m.2 cards? Wouldn't that mean each m.2 card has to be down rated to x2 lanes?

That's what's confusing me. Because I thought each m.2 card had to have the whole x4 lanes.

It's those chipset x4 lanes that allow 2 slots of m.2... if both are populated then what happens... do they down rate to x2 each or do they steal from the GFX?
 
Grim5 said:
I've got the formula x670e and it can do x16 GPU and x4 Nvme but I think it only does 1 or 2 slots at gen 5. There probably isn't any x670e boards that can do a gen 5 GPU and 4 gen 5 Nvme
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I don't care about gen 5 nvme, maybe have one in the future for OS drive only... but I do want to populate all four of the m.2s with gen 4 without affecting GFX performance.
 
Grim5 said:
Be warned if you use the gen5 expansion card from the hero it will drop the GPU to x8. I planned to use the expansion card until I found this out
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I didn't plan on using it but this has added a new confusion...

x16 PCIe lanes = GFX (total lanes: 16)
x4 PCIe 5.0 lanes (CPU) = 1 m.2 slot (total lanes: 20)
x4 PCIe 5.0 lanes (CPU) = 1 m.2 slot (total lanes: 24)

The expansion card takes x4 lanes and AMD CPUs allow 28 lanes so why can't the last 4 lanes be used for the expansion card without dropping GFX to x8?
 
Tetras said:
Yup, even a "lower-end" board can do this (like the X670E Tomahawk), if you don't care about PCI-E 5.0 :D
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Maybe 5.0 for future GPU (5090?) and future OS m.2. Do you think the Hero board is a good choice proving cost is no big deal? I heard the Intel Ethernet ports had issues in the past and the first batches of the motherboards caused explosions/fires :mad:
 
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