Help Understanding PCIE lanes and usages, it REALLY hurts my brain to think about.

SaFireSunSet

I am getting parts right now for a new build and just want to make sure the things are compatible and wont oversaturate my pcie lanes.

Proposed parts related to the question are going in an O11D evo XL case

ROG Maximus Z790 Hero Eva-02 motherboard

Intel i9 13900K cpu

MSI suprim liquid x 4090

Elgato 4k60 pro MK.2 internal capture card

1 Crucial T700 4TB PCIe Gen5 NVMe M.2 Drive set in the main m.2 slot on the board

2 Crucial T700 4TB PCIe Gen5 NVMe M.2 Drives set in the rog m.2 hypercard that comes with the motherboard, which is recommend to be put in the bottom pci slot on the board.

I just...trying to figure out how PCIe lanes and saturation works hurts my brain, and i would really appreciate it if someone could explain it like i am 5.

Additional question - Can a Gen5 NVMe work in a Gen4 slot? The PCIe slot that the Hypercard is recommended to be installed in is a Gen4 slot, if needs be I can switch the 2 Gen5 M.2s in the hypercard to 2 Gen4 NVMe Crucial P5 Plus 2TB PCIe M.2 2280SS drives if i cant put Gen5 drives in Gen4 slots.

Any Help is SUPER appreciated.

PowerSpec_MikeW

@SaFireSunSet

So M.2_1 and PCIe_1 x16 are the two slots wired to the CPU. That provides 20 lanes, 16 PCIe Gen5, and 4 PCIe Gen4. There is no native support for Gen5 M.2 drives, but they will work fine and operate at Gen4 speeds. For Gen5 on the M.2, you would need to use the included ROG Hyper card, install that in the top x16 slot, then move your video card down to the second PCIe x16, however this is going to eat up all your chipset lanes while you waste most of your CPU lanes..

So the Chipset has 20 Gen 4 and 8 Gen 3 lanes. If you do the card down there, you'd be able to do your second M.2's at Gen4. One in the lower M.2's on the chipset, the other in M.2_1 on the CPU's Gen4 lanes. I don't think the Gen5 speed is really going to be noticeable if you're just gaming. I'd keep the card up top, main drive in M.2_1 then you'll have plenty of Gen4 bandwidth for your additional NVMe drives. Though if one of the secondary drives is just a data or backup drive, you shouldn't really care about the speed potentially being capped by Gen3 either. It'll depend on how large the video card is and how it fits.

PCIe is backwards compatible. It will work, it's just going to be a potential bandwidth limitation.

Edit: Forgot to mention the El Gato. Looks like it's PCIe Gen2 x4. So you should have another 4 Gen3 lanes left over for it if the card goes in the lower PCIe slot. Being water cooled, it should be relatively slim. Also, to correct what I said above. The second PCIe x16 is also Gen5. If used both run at x8. So you won't be using up any of the Gen4 lanes from the chipset.

Configuration ideally if this will fit (top to bottom):

M.2_1 - Secondary drive. Gen4 speed.

PCIex16G5_1 - Primary drive in ROG Hyper card.

PCIex16G5_2 - GPU ( this will run at x8, but should not limit your GPU. This is Gen3 x16 which hasn't been shown to limit GPU's in benchmarks.)

M.2_2 or 3 - Last drive. Gen4 Speed.

PCIex16G4 - El Gato card.

Intel® CoreTM Processors (14th & 13th & 12th Gen)*

2 x PCIe 5.0 x16 slots (support x16 or x8/x8 modes)**

Intel® Z790 Chipset

1 x PCIe 4.0 x16 slot (supports x4, x4/x4 modes)

* Please check the PCIe bifurcation table on the support site (https://www.asus.com/support/FAQ/1037507/).

** When ROG Hyper M.2 card is installed on PCIEX16(G5)_1, PCIEX16(G5)_2 will run x8 only and if ROG Hyper M.2 card is installed on PCIEX16(G5)_2, PCIEX16(G5)_1 will run x8 only. - To ensure compatibility of the device installed, please refer to https://www.asus.com/support/ for the list of supported peripherals.

Total supports 5 x M.2 slots and 6 x SATA 6Gb/s ports*

Intel® 13th & 12th Gen Processors*

M.2_1 slot (Key M), type 2242/2260/2280/22110 (supports PCIe 4.0 x4 mode.)

Hyper M.2_1 slot (Key M) via ROG Hyper M.2 card, type 2242/2260/2280/22110 (supports PCIe 5.0 x4 mode.)**

Intel® Z790 Chipset**

M.2_2 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 mode)

M.2_3 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 & SATA modes)

Hyper M.2_1 slot (Key M) via ROG Hyper M.2 card, type 2242/2260/2280/22110 (suppports PCIe 4.0 x4 mode)**

Hyper M.2_2 slot (Key M) via ROG Hyper M.2 card, type 2242/2260/2280/22110 (suppports PCIe 4.0 x4 mode)***

6 x SATA 6Gb/s ports****

* Intel® Rapid Storage Technology supports PCIe RAID 0/1/5/10, SATA RAID 0/1/5/10.

** When ROG Hyper M.2 card is installed on PCIEX16(G5)_1, Hyper M.2_1 slot can support PCIe 4.0 x4 mode. When ROG Hyper M.2 card is installed on PCIEX16(G5)_2, Hyper M.2_1 slot can support PCIe 5.0 x4 mode. When ROG Hyper M.2 card is installed on PCIEX16(G4), Hyper M.2_1 and Hyper M.2_2 slots can support PCIe 4.0 x4 mode.

*** When ROG Hyper M.2 card is installed on PCIEX16(G5)_1 or PCIEX16(G5)_2, Hyper M.2_2 slot will be disabled. When ROG Hyper M.2 card is installed on PCIEX16(G4), Hyper M.2_1 and Hyper M.2_2 slots can support PCIe 4.0 x4 mode.

**** RAID configuration and boot drives are not supported on the SATA6G_E1-2 ports

Source: https://rog.asus.com/us/motherboards/rog-maximus/rog-maximus-z790-hero-eva-02-edition/spec/

Intel chipset features: https://www.intel.com/content/www/us/en/products/docs/chipsets/desktop-chipsets/z790-chipset-brief.html