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Maximus XI Extreme - DIMM.2 slot question

Odaik
Level 7
Hello

I am interested in purchasing one of the new MXIE motherboards when they become available, and am somewhat confused by the inclusion of the "DIMM.2" used as an expansion slot for NVME based M.2 SSDs.

It seems the main rationale behind it is the physical connections means the mounted SSDs sit in the path of the airflow in a case to assist in thermal performance. But there are also claims that this connector is somehow wired to the PCIE controller onboard the CPU itself, like the PCIE 1/2 slots used for graphics cards.

Does this mean that when using the DIMM.2 slot for 2 NVME SSDs, the bandwidth available to graphics cards will be limited? My understanding is the Intel CPUs themselves only have a maximum of 16 PCIE lanes available, so presumably only 8 are available for graphics if 8 are in use by the DIMM.2-connected devices?

There seems to be remarkably little information about how this feature would actually work. Any input would be appreciated!

Thanks
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19 REPLIES 19

Silent_Scone
Super Moderator
Hi,

The DIMM.2 slot is wired to 8x PCIE lanes. The CPU will allow for 1x16, 2x8, 1x8+2x4 configurations. So with two NVME drives connected to DIMM.2 the GPU will run at x8, correct. The performance difference between the two lane speeds is negliable, sometimes none existent , in fact.
13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

Mr__Fox
Level 12
The reduction in speed is relevant to the chipset and CPU. If you go with X299 the DIMM.2 will not slow down the PCIe speed to 8x with the right CPU because you will have ample PCIe lanes.

With my setup, I have dual DIMM.2 cards and a total of 4 NVMe drives (2 on each DIMM.2) and the GPU still runs at full bore 16x.
Wraith // EVGA Z690 Dark K|NGP|N | 13900K | RTX 4090 Suprim | 32GB DDR5 Hynix A-DIE @8200 | SuperNOVA 1600 P2 | HC-500A Chiller | MO-RA3 360 || DG-86
Banshee // ROG Z690 Apex | 13900KF | RTX 3090 K|INGP|N | 32GB DDR5 Hynix A-DIE @ 6800 | Corsair RM122x SHIFT | XT-45 NOVA || 5000D Airflow
Half-Breed // Precision 17 7720 | 7920HQ (BGA filth) | Quadro P5000 16GB (MXM) | 32GB DDR4 || Grade A Off-Lease Refurb

Mr. Fox wrote:
The reduction in speed is relevant to the chipset and CPU. If you go with X299 the DIMM.2 will not slow down the PCIe speed to 8x with the right CPU because you will have ample PCIe lanes.

With my setup, I have dual DIMM.2 cards and a total of 4 NVMe drives (2 on each DIMM.2) and the GPU still runs at full bore 16x.


Dear Mr. Fox!

Would you please tell me, that configuration do you use?

I'm confused a bit and would appreciate any help. I would like to build a new rig, using at least 2 pieces of 970 EVO M.2. This SSD has a maximum read speed of 3500 MB/s. If I buy Maximus XI Formula or Extreme +9900K, I can't use the two M.2 drives in a PCIe slot (with a PCIe card or DIMM.2), becouse I will not want to have X8 bandwidth for my graphics card instead of X16 (I know, the difference is marginal, but with new RTX cards there actually will be some FPS difference). If I insert the two M.2 SSDs into the onboard slots, than I will be bottlenecked by the chipset, becouse DMI bus will allow only 3,9 GB*s in total. So, another choice could be an Asus Rampage Deluxe II + 9900X. In this case, I would have enough PCIe lanes for all my M.2 cards to run at full speed + X16 for my video card. But X processors haveless boost speeds than for example 9900K (5Ghz on two cores or overclocked to all). So perhaps X processors are not as effective for games as 9900K (?). But here comes another dilemma. If I use two M.2 SSDs on the board slots and not raiding them, would the DMI bus speed really matter that much in reality? For example when copying files from one drive to another?

Thanks!

PsiEmitter wrote:
Dear Mr. Fox!

Would you please tell me, that configuration do you use?

I'm confused a bit and would appreciate any help. I would like to build a new rig, using at least 2 pieces of 970 EVO M.2. This SSD has a maximum read speed of 3500 MB/s. If I buy Maximus XI Formula or Extreme +9900K, I can't use the two M.2 drives in a PCIe slot (with a PCIe card or DIMM.2), becouse I will not want to have X8 bandwidth for my graphics card instead of X16 (I know, the difference is marginal, but with new RTX cards there actually will be some FPS difference). If I insert the two M.2 SSDs into the onboard slots, than I will be bottlenecked by the chipset, becouse DMI bus will allow only 3,9 GB*s in total. So, another choice could be an Asus Rampage Deluxe II + 9900X. In this case, I would have enough PCIe lanes for all my M.2 cards to run at full speed + X16 for my video card. But X processors haveless boost speeds than for example 9900K (5Ghz on two cores or overclocked to all). So perhaps X processors are not as effective for games as 9900K (?). But here comes another dilemma. If I use two M.2 SSDs on the board slots and not raiding them, would the DMI bus speed really matter that much in reality? For example when copying files from one drive to another?

Thanks!
Sorry for the delayed reply. You may be overthinking the process too much. Prior to my current setup I had a Maximus X Hero (WIFI-AC) motherbord with an 8700K CPU and 1080 Ti. I had both of the M.2 slots populated with a 960 Pro and my 1080 Ti ran at 16x with no issues.
Wraith // EVGA Z690 Dark K|NGP|N | 13900K | RTX 4090 Suprim | 32GB DDR5 Hynix A-DIE @8200 | SuperNOVA 1600 P2 | HC-500A Chiller | MO-RA3 360 || DG-86
Banshee // ROG Z690 Apex | 13900KF | RTX 3090 K|INGP|N | 32GB DDR5 Hynix A-DIE @ 6800 | Corsair RM122x SHIFT | XT-45 NOVA || 5000D Airflow
Half-Breed // Precision 17 7720 | 7920HQ (BGA filth) | Quadro P5000 16GB (MXM) | 32GB DDR4 || Grade A Off-Lease Refurb

Hopper64
Level 15
I was looking for a definitive answer to this lane allocation question on the M11E too. If I use the dimm.2 with one SSD that still might decrease the graphics card to 8x, but is there a bios setting to switch the dimm.2 to the PCH? The top and bottom slots on the board are not connected to the CPU so I could use an adapter in the very top slot and run the SSD via the PCH. Anyone know for sure?
MZ790A Bios 2002, GSkill F5-8000J3848H16GX2-TZRK, 13900KS, EKWB D5 TBE 300, Seasonic Prime TX-1600 ATX 3.0, Asus Strix 4090 w/ Optimus block, Phanteks Enthoo Elite, Asus Claymore 2, Asus Gladius 3, Asus XG349C, Samsung 990, Windows 11 Pro

Hopper64 wrote:
I was looking for a definitive answer to this lane allocation question on the M11E too. If I use the dimm.2 with one SSD that still might decrease the graphics card to 8x, but is there a bios setting to switch the dimm.2 to the PCH? The top and bottom slots on the board are not connected to the CPU so I could use an adapter in the very top slot and run the SSD via the PCH. Anyone know for sure?


I'm also looking for a clear answer to this. If I have one M.2 in the Dimm.2 riser card how can I still retain the PCIE at 16x?

MorePower wrote:
I'm also looking for a clear answer to this. If I have one M.2 in the Dimm.2 riser card how can I still retain the PCIE at 16x?


no. 9900k or any other 1151 processor only has 16 pci lanes. Running one card on dimm2 still drops it to x8.*

Hello Guys,

i got the Maximus Extrem XI and put 2 SSD in the Dimm.2 Slot. I got on my GPU only x8 lanes. I think this Slot is usless if there is no chance to get x16 lanes.

Odaik
Level 7
Thanks for the responses guys, that explains it.

I echo Hopper64's sentiment though - is there a way to have these slots run through the PCH instead?