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

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.

12-14th gen & Z790 can't support 1.
 
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.
Click to expand...
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).
 
SquirrelMadness said:
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).
Click to expand...
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.

The X670E-E Strix has the same issue, it tries to give you 3x PCI-E 5.0 M.2 slots, one of which is stolen from the graphics card lanes.

The X670E-Plus Tuf doesn't have this, because it only has 1x PCI-E 5.0 M.2 slot (2x PCI-E 4.0 and 1x PCI-E 3.0).
 
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.
Click to expand...
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:
 
SquirrelMadness said:
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.
Click to expand...
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.
 
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.
Click to expand...

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?
 
SquirrelMadness said:
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).
Click to expand...


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
 
SquirrelMadness said:
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:
Click to expand...


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
 
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
Click to expand...
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
Click to expand...
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?
 
Ryzen 7000 has 28 PCI-e 5 lanes in the CPU (4 of which are for the downlink to the chipset) so 24 user config

16 for the GPU or x8x8 if using 2 GPU's etc
4 + 4 PCI-e 5.0 lanes generally most use this for 2 x nvme slots on the higher end boards (x670e)

The rest of the lanes are PCI-e 4.0 and are supplied by the chipset(s) X670e has 2 chipsets.
 
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
Click to expand...
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:
 
SquirrelMadness said:
I heard the Intel Ethernet ports had issues in the past and the first batches of the motherboards caused explosions/fires :mad:
Click to expand...

Explosions and fires?!

It was about 5 CPU’s worldwide that burned out. There were no explosions or fires.

The Hero is a great board, if somewhat expensive. But that’s a given.
 
Sorry for resurrecting this thread after 10 months but I do have a question regarding X670E-E Strix and its PCI lane sharing.

CPU: Ryzen 7 7700
GPU: RTX 4080
NVMe 1: Kingston KC3000 2TB (Gen4)
NVMe 2: Samsung 970 Evo Plus 2TB (Gen3)

Future purchase:
NVMe 3 and 4: Kingston KC3000 4TB (Gen4)

As I understood, if NVMe SSD is inserted to slot 3, GPU slot (PCI-E 1) drops from 16x to 8x, but if its Gen5.

So question is: if I populate Kingstons 3x KC3000 Gen4 in slots 1, 2 and 4, and "slowest" Samsung Gen3 in slot 3, could I have 16x on GPU/PCI-E 1 since no device is Gen5, neither SSDs or GPU?

And, does that Alteration Mode switch on-board can help with that to set only Gen4 signal from CPU?

All I want is having 4x NVMe M.2 drives (3x gen4 + 1x gen3) and 16x GPU. Is that possible in any combo or I f-ed up myself when bought X670E-E :) ?

Many thanks.
 
Ravenholm said:
So question is: if I populate Kingstons 3x KC3000 Gen4 in slots 1, 2 and 4, and "slowest" Samsung Gen3 in slot 3, could I have 16x on GPU/PCI-E 1 since no device is Gen5, neither SSDs or GPU?
Click to expand...
No, it is not possible.

The lane sharing is hard wired, so the gen is not relevant.

Ravenholm said:
Is that possible in any combo or I f-ed up myself when bought X670E-E :) ?
Click to expand...
The reason it shares lanes with the GPU is because they offer 3x PCI-E 5.0 M.2 slots, if you wanted to run 4x M.2 with no impact then you would have needed a board that only has 2x PCI-E 5.0 M.2 slots.

I think you might be able to do this by placing an expansion card for 1x M.2 slot, in the third full-length PCI-Express slot at the bottom of the board. (And leave M.2 slot 3 empty)
 
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