Looking at options for installing an additional SSD on my system in particular whether or not to avail myself of the DIMM.2 module featured on my Maximus XI Extreme motherboard.

I understand that if you populate both slots of the DIMM.2 module with M.2 drives the number of PCIe lanes available to the GPU in the primary slot drops to x8.  However I am unclear as to what happens if you only populate one of the two M.2 slots on the DIMM.2 module - does the GPU still run at x8 and if so does it matter?  Utilizing the DIMM.2 module is a very simple process whereas installing M.2 drives in the slots directly on the motherboard is much more complicated you have to remove the GPU and deal with PCH heatsink screws that tend to strip.

Thank you

Bruceb

On my motherboard (ASUS Maximus X Hero WiFi) if you have both M.2 slots used, it disables SATA ports 5 and 6.   My impression is that a lot (all?) of the Z370 boards are this way...but I don't know about newer chipset boards like your Maximus XI.  Check your motherboard manual.  Also, the BIOS should have notes about using x2 or x4 modes and what it disables.

As for the mounting of M.2 drives, I agree, it is not the most confidence-insipiring design.  On my board the first M.2 port has a heat sink, and the second M.2 slot just has the drive sitting there at an angle.  I wouldn't feel good about screwing and unscrewing that multiple times, but my hope is that it won't happen often.  I just added a 1TB 2.5" SSD to my dual M.2 setup, and I did forget, and tried to install it to Port 6 because it was the easiest port to access, without having to take out the vidcard.  I ended up having to unhook everything from the box, and put the case on my work table and gently remove the 1080ti card so that I could plug the SSD cable into a lower port.  More work than I wanted to do, but it's done now.

Also would have helped if I had remembered to plug the power cable into the SSD.  I think I'm losing my skills.  😬

Thank you for your observations but what i was really after was some insight into how utilizing the DIMM.2 slot featured on Maximus XI Extreme motherboards impacts GPU performance.  This issue has some history on other forums but getting a clear answer has been difficult and the ASUS motherboard manual is of little help with just a short cryptic note.  

So in a nutshell what I would like to know is

1.  Does using one M.2 drive in the DIMM.2 slot reduce primary GPU PCIe lanes from 16 to 8 - it definitely does with two but I am unsure about just one?

2  If the primary GPU is reduced to 8 PCIe lanes does it matter - would you notice anything in the real world?

Thank you

Bruceb

Hi Bruce,

 

Not sure if this helps, but each SSD consumes PCIe 3x4. so by using both SSDs a total of 8 lanes would be utilized.For one SSD its not clear as you said.

More info here: https://linustechtips.com/main/topic/956268-asus-dimm2-riser-card-bandwidth/

 

Also here, it appears you can configure DIMM 2.1 in the BIOS (I assume with a single M2 SSD) and utilize the PCIE16_2 slot.

https://www.back2gaming.com/guides/how-to-enable-m-2-on-maximus-xi-extreme/

By deduction I would say even with one M2 SSD mounted in the DIMM2 riser module, you are going to lose 8 PCIE lanes.

 

Regards
Mark

 

 

My install did not seem to hamper the GPU

On 4/18/2020 at 12:42 AM, brucewtb said:

Looking at options for installing an additional SSD on my system in particular whether or not to avail myself of the DIMM.2 module featured on my Maximus XI Extreme motherboard.

I understand that if you populate both slots of the DIMM.2 module with M.2 drives the number of PCIe lanes available to the GPU in the primary slot drops to x8.  However I am unclear as to what happens if you only populate one of the two M.2 slots on the DIMM.2 module - does the GPU still run at x8 and if so does it matter?  Utilizing the DIMM.2 module is a very simple process whereas installing M.2 drives in the slots directly on the motherboard is much more complicated you have to remove the GPU and deal with PCH heatsink screws that tend to strip.

Thank you

Bruceb

Bruce,

I installed 2x 2Tb NVme sticks into the M.2 slots MSI MPG Gaming Edge board along w/ a 9900K and an RTX 2070 Super.  I did not know about this issue but when I run for example Passmark's suite of GPU benchmarks the numbers are right where one would expect them to be so I guess it's not coming into play very much if at all.  It's all running stellar including very rapid boot-ups and load times for P3D files.  The 2nd NVme drive I could technically remove it's only there as a backup location for images of the 2 OS installs on the first NVme drive, one partition for P3D 4.x, the other patiently waiting for MSFS.  But it's handy to do a rapid image so I think I'll just leave it as is.

i have the maximus xi hero with 2 M2's and graphics card still running at X16.  Like somebody said above.  You just lose two sata ports. 

7 hours ago, micstatic said:

i have the maximus xi hero with 2 M2's and graphics card still running at X16.  Like somebody said above.  You just lose two sata ports. 

I went to look myself and indeed the GPU is running at 16x.

Thank you for these replies.  Just by way of clarification installing M.2 drives in the the M.2_1 and or the M.2_2 sockets that most current generation MBs have  does not have any bearing on GPU PCIe lane usage this only comes into play when you install M.2 drives into the DIMM.2 slot that is available on the high end Maximus XI Extreme MB and possibly others.  From what I can make out this issue would have very little impact on the performance of a 1080ti that I have and maybe about 3% on a 2080ti but could become more significant for future GPUs down the track which is my main concern. I'm inclined now to just go with a 2.5 inch SATA 2 or 4 tb SSD as from what I also understand the very high speed of M.2 drives is throttled by current generation CPUs.

Bruceb

6 hours ago, brucewtb said:

I'm inclined now to just go with a 2.5 inch SATA 2 or 4 tb SSD as from what I also understand the very high speed of M.2 drives is throttled by current generation CPUs.

Bruceb

Nuttin' throttled in any way significantly by my 9900K and my two NVme sticks in their respective M.2 slots.  Boot times are ultra fast, as are reloading scenery when you make a change in the Scenery GUI.  Running Disk Mark or AIDA64's disk bench puts them at 2600mb/sec +/- a few mbs.  The old SATA HDD gets 92mb/sec on the same bench.   And CPU utilization nears 0% on the two NVme sticks.  Hard to beat really and the price was very decent at $229 per I used the 2nd stick only for clones/images of the first and some data.

Is your old drive the spinning rust type or an SSD?  I could install an M.2 drive in the unoccupied M.2_2 socket (M.2_1 has a small M.2 with just the OS) but it will be a PITA to do so and will lose SATA 5&6. Comparing load times with the M.2 drive on my P3D PC with my other PC which has the OS on a SATA SSD I find no difference both are very fast compared to spinning rust drives.

Bruceb

1 hour ago, brucewtb said:

Is your old drive the spinning rust type or an SSD?  I could install an M.2 drive in the unoccupied M.2_2 socket (M.2_1 has a small M.2 with just the OS) but it will be a PITA to do so and will lose SATA 5&6. Comparing load times with the M.2 drive on my P3D PC with my other PC which has the OS on a SATA SSD I find no difference both are very fast compared to spinning rust drives.

Bruceb

Yes that was an old data spinning platters HDD I took out of the former box so I was able to test it in my new PC.  And yes the new NVme in the M.2 is roughly 5x faster than the SATA III SSD I had in the former box.  It manifests immensely in system boot time, less so in loading P3D flights because presumably that entails more than reading/writing from the drive, and immensely when making a change in the world scenery GUI when the scenery has to reshuffle and load.   I feel fortunate to have 2x2Tb of these drives they're so simple and light weight I love it.  Literally the size of a stick of gum.  I hope they hold up!  Around 1990 I bought my first custom built PC and splurged for the massive Maxtor 5,400 rpm 120 megabyte HDD--it was around $150!  And 8mb of ram too!

Do you know if it's possible to completely take a SATA port or M.2 port offline in the BIOS?  If it is I'd like to clone rather than image as it seems you can have problems w/ cloned drives both active in the same machine, and as you point out it is a PITA to remove one they're rather delicate the GPU needs to come out to get to them easily or at all in the case of the M.1 slot.  But still it would be cool to be able to take the 2nd disk offline in the BIOS until time to reclone or make the drive active.