Asus ROG Strix z490-e gaming dosent have 2xPICE 16x channels???

hello there,

im melkanea & this is my first post!

so i was sadly surprised when i added the nvme extention card & it required a PICe bifurcation of 4x4x4x4 for 4 512GB M2 nvmes which would have worked with a primary pice 16x & a secondary 16x for my GPU
but instead of having 2 pcie 16x slots the Mb opts for going 8x/8x which means the nvme card only had 4x4x for nvmes & 2 would never be detected as they had no channels asigned to them...

i mean i spend 283€ on it, it had everything id wished for to code at fullstacker level (virtualization & TPM to get win 11 to go dev mode cus wsl & vscode just love each other) & run heavily moded game servers
while maxing out on 2K gaming & streaming at 4K

the plan i had for my machine, my most powerfull & favorite build since overclocking the 144mhz MMX cpus with a HB pencils!
its like my dream broke... & im not sure if its just a lazy oversight from the engineers or an intentional limitation designed by the manufacturers to piddle of a niche of gamers... mid range MBs always had 2 x 16x channels, at least if they brag dual GPU setups... cus 2 GPUs at 8x is just a single CPU at 16x meaning they are literally scaming uswhat id really hope for is if the thigs has a BIOS solution... like if the MB goes 8x/8x for compatibility mode or not to stress the HW, which would mean an update or BIOS customization could actually solve my case...

i mean the 16 hardwache channels must be handled by the MB, if my ports can go 8x8x whats stoping it from going 4x4x4x4, its not like 1x cahnnels arent real... it might not be efficient or stress the hardware a bit but i doubt its imposible.

since im a OS level developer i got no clue of BIOS & would lve to know if anyone got any clues tips or suggestions

I believe that the maximum number PCI-E lanes for that system would be 24.

If the two X16 slots are populated, each slot would be assigned 8 lanes.

It's a hardware limitation. No BIOS setting can increase that.

I have a Z690-E motherboard, with a similar PCI-E lane limitation. It came with a "Hyper M.2" accessory card, but it supports only two M.2 NVME cards.

I'm not sure what would be the most minimal system is that would give you more than 32 PCI-E lanes. Maybe an AMD Ryzen 7000 series, with an X670 or X670E chipset. https://www.amd.com/en/product/12151

HEDT (high end desktop) systems have lots of PCI-E lanes, at a higher price. If you prefer Intel, the latest HEDT machines they sold were Gen10, with an X299 chipset (Socket 2066). Intel® Core™ i9-10980XE Extreme Edition Processor (24.75M Cache, 3.00 GHz) - Product Specifications | Intel

Intel CPU have only 20 PCI-E lanes (the PCI-E comes off the motherboard. 16 are normally dedicated to graphics. The minimum you can have for graphics is 8 lanes so that only leaves you 12 to work with. I don't know how your board is configure, but the it probably dedicates 4 to an onboard m.2 nvme. Take away that 4 leaves 8 lanes so what you see wit 2x4 is expected. I will check your motherboard manual, maybe you can disable that onboard m.2, giving you 3x4 on your card.

I don't think this will help. From your manual below is a similar Asus card (Hyper m.2 x 16). It looks like you can only get 16 lanes to it lanes if you put the card in the primary graphics card slot, which would lead you with the CPU graphics and no discrete graphics card possible. If you put it in the secondary graphics card slot, you can only use 2 of the m.2 on the card, but would be able to use a discrete graphics card at x8 lanes.

Actually a correction. The 10th gen processors only have 16 total lanes coming from the CPU. So there you there you are, stuck with 4x+4x. Newer CPU have 20 lanes.

bobkn said:

I believe that the maximum number PCI-E lanes for that system would be 24.

If the two X16 slots are populated, each slot would be assigned 8 lanes.

It's a hardware limitation. No BIOS setting can increase that.

I have a Z690-E motherboard, with a similar PCI-E lane limitation. It came with a "Hyper M.2" accessory card, but it supports only two M.2 NVME cards.

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sucks so many user machines ome with such silly limitations, either choose from a GPU or high speed storage

PerpetualCycle said:

I don't think this will help. From your manual below is a similar Asus card (Hyper m.2 x 16). It looks like you can only get 16 lanes to it lanes if you put the card in the primary graphics card slot, which would lead you with the CPU graphics and no discrete graphics card possible. If you put it in the secondary graphics card slot, you can only use 2 of the m.2 on the card, but would be able to use a discrete graphics card at x8 lanes.

View attachment 91244

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this the 4xNVME card i got
it requires 4x4x4x4 bifuraction 8x4x4x was suposed to see 3x nvmes but it wont as my pcie goes 8x8x
so basically my CPU is limiting my pcie lanes?
i think im gona move the card to my tiny server, i guess if i remove its GPU i can run it at 16x which would be 4x4x4x4x

my machine

melkanea said:

this the 4xNVME card i got
it requires 4x4x4x4 bifuraction 8x4x4x was suposed to see 3x nvmes but it wont as my pcie goes 8x8x
so basically my CPU is limiting my pcie lanes?
i think im gona move the card to my tiny server, i guess if i remove its GPU i can run it at 16x which would be 4x4x4x4x

my machine

Click to expand...

Yes, you only have two x16 slots and both are from the CPU, which has only 16 lanes. If you put a graphics card in both they become x8 + x8 . If you put your card in they become x8 + x8. The only possible solution I can think of that might work is if you use the CPU's graphics, take your graphics card out, put your m.2 card in the main x16 slot in its place, and put nothing in the second. But you have an F CPU with no graphics so would not be able to do that if it were possible.

Been like that on Intel for consumer based CPU. It is limitations: How many PCI lanes can be added to the CPU within cost, size and power limitations. Lanes are not logical things, they are burned in routed traces on the motherboard and to be able to allocate at all requires low level circuit programing and switches on the motherboard. This also adds cost.

Newer processors have 20 lanes, with 4 dedicated to a CPU PCI x4 m.2 on the board. All the other m.2 are off the chipset. PCI-E (and I am not aware of any motherboard that has made a chipset PCI-E x16 slot).

AMD Ryzen had more lanes available before Intel. I had a spare i9-10850k cpu. So I bought a Z590 motherboard vs the older Z490. Unfortunately the older 10850k didn't fully support the Z590 chipset especially with lane availability. I had to go ahead and get an 11th gen processor. Even just to use a Gen 4 NVMe drive....well the top slot anyway.

PerpetualCycle said:

Yes, you only have two x16 slots and both are from the CPU, which has only 16 lanes. If you put a graphics card in both they become x8 + x8 . If you put your card in they become x8 + x8. The only possible solution I can think of that might work is if you use the CPU's graphics, take your graphics card out, put your m.2 card in the main x16 slot in its place, and put nothing in the second. But you have an F CPU with no graphics so would not be able to do that if it were possible.

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since im wasting 2 nvmes on my extender card i might just try & put the card in the server where i remove the GPU cuss it dosent need a screen. i can login with ssh anyways & everything else should be available from the net

BamaInArk said:

AMD Ryzen had more lanes available before Intel. I had a spare i9-10850k cpu. So I bought a Z590 motherboard vs the older Z490. Unfortunately the older 10850k didn't fully support the Z590 chipset especially with lane availability. I had to go ahead and get an 11th gen processor. Even just to use a Gen 4 NVMe drive....well the top slot anyway.

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yaahhh, im recicling an old very old MB & CPU, it can barely reach 12GB ram with 4 chips

The Gigabyte Z790 Aorus Elite X has four onboard M.2 NVMe 4.0 x4 sockets all four of which can be in use without causing the PCIe 5.0 x16 slot to drop to x8. The only real "downside" with this particular mobo from Gigabyte in that regard is that none of the onboard M.2 sockets support NVMe 5.0.

If you could live with 2 M.2 drives in the expansion card, that might be simplest.

hdmi said:

The Gigabyte Z790 Aorus Elite X has four onboard M.2 NVMe 4.0 x4 sockets all four of which can be in use without causing the PCIe 5.0 x16 slot to drop to x8. The only real "downside" with this particular mobo from Gigabyte in that regard is that none of the onboard M.2 sockets support NVMe 5.0.

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That is because they are using the chipset PCI-E, not the CPU PCI-E. I also have 5 on-board m.2 slots on my z590. One is PCIE-5 from the CPU and the other 4 PCIE-4 from the chipset. The ones off the chipset have to be routed to the CPU via the DMI link (processor to chipset high speed data link)., so can be inferior in that respect too.

PerpetualCycle said:

That is because they are using the chipset PCI-E, not the CPU PCI-E. I also have 5 on-board m.2 slots on my z590. One is PCIE-5 from the CPU and the other 4 PCIE-4 from the chipset. The ones off the chipset have to be routed to the CPU via the DMI link (processor to chipset high speed data link)., so can be inferior in that respect too.

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Yes, but the DMI link uses 8 PCIe 4.0 lanes so, even though it certainly is true that the 3 M.2 sockets that are limited by this can become a real "bottleneck", in practice it should happen only very rarely and/or happen for only very short periods typically, under most circumstances and especially if talking about the kind of circumstances that can be considered to be in line with the intended use, that these types of motherboards are designed for, factually.

To elaborate, the AMD Z690/Z690-E can be inferior due to it using only 4 PCIe 4.0 lanes to connect itself to the CPU, as this limits the maximum total transfer speed of all I/O features that belong to the chipset combined, when compared to the 8 PCIe 4.0 lanes in the DMI 4.0 of the Intel Z790. So, it's more a question of whether this sacrifice in all the other types of I/O features will be worth that ability, i.e., the ability to scrape that last grain of total/combined NVMe speed from underneath the soles of Z690/Z690-E. I don't doubt the fact that it can be. (But then, you could always decide to just aim for a server motherboard...)

Also consider the fact that it is possible to avoid this particular limitation by choosing a graphics card that has an M.2 socket on it. As you probably know, none of the latest/greatest GPUs (Radeon RX 7900 XTX or GeForce RTX 4090 Ti) are capable to use the bandwidth that PCIe 5.0 x16 can offer, as these GPUs can still only use up half of this maximum so, it makes sense to make a GPU card that lets you utilize the second half for NVMe expansion.

Another thing to note is that the Z790 Aorus Elite X can support Intel 14th Gen CPUs, that, depending on the CPU model of course, let you use integrated Intel ARC graphics, and that is a substantial improvement over the integrated Intel Iris Xe graphics found in previous generation CPUs from Intel. This makes the option to use the PCIe 5.0 x16 slot for expanding the total number of M.2 NVMe sockets [as opposed to use it for discrete graphics] an even more attractive choice to maybe want to consider, when compared to how it used to be with previous generation Intel CPUs. Not that integrated ARC graphics can in any way compete with any of the more decent discrete graphics cards of course. It can't. But anyway.

^All of which is completely irrelevant to this discussion of a z490 board

Regardless of whether you have a Z490 through Z790 board, I believe that none offer two X16 slots with the full 16 lanes each.

PerpetualCycle said:

^All of which is completely irrelevant to this discussion of a z490 board

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The OP asked for tips or suggestions. So, I replied.