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Using multiple M.2 SSDs on a Maximus XI motherboard

PsiEmitter
Level 8
Hi Everyone!

Please, be so kind to help me out in the following issues, since I'm not an expert in these matters.

I'm planning to build a new rig around a Maximus XI motherboard. I would like to use four M.2 NVME SSDs: 2x970 EVO 2TB and 2x970 EVO 1 TB. I don't want to use any other type of storage (f.e. SATA III SSD), only the four M.2 SSDs mentioned above. My questions are the following:

1. Assuming I would use Maximus XI Extreme, I could insert two SSDs into the onboard M.2 slots, and the other two into the provided adapter using the DIMM.2 slot. In this case, will I be able to run all my four M.2 SSDs at their maximum write and read speeds, or will there be any bottlenecking factors?

2. Maximus XI Formula doesn't have a DIMM.2 slot, so in this case I can only use the two onboard M.2 slots. Is there any option - like a PCI-E M.2 adapter card, or similar - that would make me possible to add the remaining two M.2 SSDs as well in order to use all four M.2 SSDs in my rig? If this is possible, will I still be able to run all four M.2 SSDs at their maximum write and read speeds?

3. If I used two M.2 SSDs in RAID 0, would this significantly increase the read and write speeds in my system?

Thank you so much for your answers in advance!
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41 REPLIES 41

HiVizMan
Level 40
Hello PsiE


Give me a couple of hours and I will be able to answer that question re the Extreme board. Have 4 M.2 SSDs that I can test and confirm one way or another. Just need to set up as the board only got here this afternoon.
To help us help you - please provide as much information about your system and the problem as possible.

I always thought there were 3x M.2 total on the Extreme... one just bellow the chipset and 2 on the riser card by the RAM

HiVizMan
Level 40
The DIMM 2 Modul supports 2 x M.2 so that does make 4 in total.

Not 100% sure it will work till I give it a go.
To help us help you - please provide as much information about your system and the problem as possible.

HiVizMan wrote:
The DIMM 2 Modul supports 2 x M.2 so that does make 4 in total.

Not 100% sure it will work till I give it a go.


Thanks so much, if you give it a try, I appreciate!

Silent_Scone
Super Moderator
Hi, the onboard slots are wired via the PCH, so are bottlenecked by the DMI bus. It is also possible to use all four at the same time.
13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

Silent Scone@ASUS wrote:
Hi, the onboard slots are wired via the PCH, so are bottlenecked by the DMI bus. It is also possible to use all four at the same time.


Hi! Thanks for your response! Does this mean, that if I use the onboard M.2 slots, I won't be able to use my M.2 SSDs at their maximum write and read speeds? Is this becouse the DMI 3.0 has a maximum throughput of 3.94 GB/s? 970 EVO 2TB has max read speed of 3500 mb/s, and write speed of 2500 mb/s. But doesn't NVME connect straight to the PCIe bus?

So all in all: is the main purpose of DIMM.2's existence to use M.2 drives through DIMM.2 and gain maximum write and read speeds of SSDs without any bottleneck?

PsiEmitter wrote:
Hi! Thanks for your response! Does this mean, that if I use the onboard M.2 slots, I won't be able to use my M.2 SSDs at their maximum write and read speeds? Is this becouse the DMI 3.0 has a maximum throughput of 3.94 GB/s? 970 EVO 2TB has max read speed of 3500 mb/s, and write speed of 2500 mb/s. But doesn't NVME connect straight to the PCIe bus?

So all in all: is the main purpose of DIMM.2's existence to use M.2 drives through DIMM.2 and gain maximum write and read speeds of SSDs without any bottleneck?


You can benchmark the speeds within Crystal Disk, the penalty shouldn’t be that great. DIMM.2 utilises CPU lanes, the others as stated above are via the PCH.
13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

Silent Scone@ASUS wrote:
You can benchmark the speeds within Crystal Disk, the penalty shouldn’t be that great. DIMM.2 utilises CPU lanes, the others as stated above are via the PCH.


And what about using two 970 EVOs in DIMM.2 slot, and the other two in a PCIE expansion card instead of onboard slots? Would this combination let me use the NVME SSDs full write and read speeds?

PsiEmitter wrote:
And what about using two 970 EVOs in DIMM.2 slot, and the other two in a PCIE expansion card instead of onboard slots? Would this combination let me use the NVME SSDs full write and read speeds?



There are 16 CPU PCIe lanes. If you mount two X4 drives on the DIMM.2 module, it will occupy eight of them, leaving eight PCIe lanes for other cards. If you mount a further two X4 M.2 drives on a PCIe card, you will have no CPU PCIe lanes left for other cards (such as a graphics card).

For your info, the DMI Bus is limited to 32Gbps. That bandwidth is shared by all devices that are connected to the PCH. If the two onboard M.2 drives are not configured as a RAID array, access will be (or should be) independent, so the performance impact should not be large. If configured as RAID 0 array, reads will be bottlenecked by DMI bandwidth.