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Crosshair X670E Extreme, confused over PCIe X16 X8 X4 with M.2 and Gen-Z.2

Rob_Ainscough
Level 7
My plan was to put my 4090 in PCIEX16_1 to run X16.

But the manual seems to suggest if I install an M.2_1 or M.2_2 or Gen-Z.2 I'll but stuck with PCIEX16_1 at 8X and my M.2's at 4X?

Puzzled at what configuration I should be using ... should I put my two Samsung 980 Pro 2TB 2280 M.2's in the single Gen-Z.2 module or put them in the M2_1 and M2_2 slots on the motherboard?

Thoughts?

Cheers, Rob.
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16 REPLIES 16

Qwinn
Level 11
Rob Ainscough wrote:
My plan was to put my 4090 in PCIEX16_1 to run X16.

But the manual seems to suggest if I install an M.2_1 or M.2_2 or Gen-Z.2 I'll but stuck with PCIEX16_1 at 8X and my M.2's at 4X?

Puzzled at what configuration I should be using ... should I put my two Samsung 980 Pro 2TB 2280 M.2's in the single Gen-Z.2 module or put them in the M2_1 and M2_2 slots on the motherboard?

Thoughts?

Cheers, Rob.


I have the same board. I believe that you can have a single M.2 in the primary M.2 slot (M.2_1) without costing your GPU lanes, but that's it (source - page 1-12 of the manual, it only mentions M.2_2 as costing lanes). Anything in PCIEX16_2 takes lanes from PCIEX16_1 too. I believe latest Intel is even worse - you cannot have any M.2 installed without costing your GPU lanes. It's kinda ridiculous.

Rob_Ainscough
Level 7
Thanks for the response.

It's confusing because M.2 Gen 4 are X4 ... the lanes supported are X16 X8 and X4 ... I don't understand why two X4 M.2 Gen4 SSDs would force PCIEX16_1 to 8X?

So where does the Gen-Z.2 fit into all this (it can house two M.2)?

So basically I have to buy ONE 4TB M.2 Gen4 X4 (rather than use my existing 2 2TB M.2 Gen4s) and my 4090 and that's it? Ugh.

Cheers, Rob.

Qwinn
Level 11
Does the Gen-Z.2 use only four lanes, or eight, given it can house two M.2s? I'm not sure. If it's eight, that would explain it. There's really only 4 to spare. At least we're not Intel, they don't even get that much.

gontch
Level 7
Rob Ainscough wrote:
My plan was to put my 4090 in PCIEX16_1 to run X16.

But the manual seems to suggest if I install an M.2_1 or M.2_2 or Gen-Z.2 I'll but stuck with PCIEX16_1 at 8X and my M.2's at 4X?

Puzzled at what configuration I should be using ... should I put my two Samsung 980 Pro 2TB 2280 M.2's in the single Gen-Z.2 module or put them in the M2_1 and M2_2 slots on the motherboard?

Thoughts?

Cheers, Rob.


Hi Rob,

For the optimal performance you should install your nvme drives in the slots that are served by the CPU directly and are not bifurcated.

On x670e extreme the fastest slots are
M.2_1
GEN-Z.2_1 (on the right side of the card)

Avoid M.2_2 as it is shared with PCIEX16_1 (where your GPU should be) and GEN-Z.2_1 as it's connected via X670e chipset that is sharing the lanes with other devices such as LAN and USBs.

Hope this helps,
Max

Rob_Ainscough
Level 7
Hi Max,

Thanks for the response, so my best performance setup is:

4090 (or 7900XTX when released) in PCIEX16_1
#1 M.2 SamSung 980 Pro 2TB in M.2_1 (on motherboard)
#2 M.2 SamSung 980 Pro 2TB in GEN-Z.2_1 (front or rear, not sure your reference point for Left/Right?)

96169

Will that keep PCIEX16_1 at X16?

Cheers, Rob.

Rob, that's my understanding reading the manual. If you try it, please report back on whether this works to keep the GPU at X16.

Rob Ainscough wrote:
Hi Max,

Thanks for the response, so my best performance setup is:

4090 (or 7900XTX when released) in PCIEX16_1
#1 M.2 SamSung 980 Pro 2TB in M.2_1 (on motherboard)
#2 M.2 SamSung 980 Pro 2TB in GEN-Z.2_1 (front or rear, not sure your reference point for Left/Right?)

96169

Will that keep PCIEX16_1 at X16?

Cheers, Rob.

F1Aussie
Level 11
I bought the Strix mobo because it can run 3 m.2 without taking lanes. Two from CPU and one from chipset. You may be more limited in the extreme because it has thunderbolt / USB and I believe they take lanes too.

Rob_Ainscough
Level 7
I've actually put both M.2's in Gen-Z.2 unit.

Unfortunately, after installing a clean Win11 ... when I shut my PC down it seemed to be "off", but 14 hours later after work I came home and my PC was on?? I use external vapor chiller that turns on externally so I was getting ZERO cooling ... I suspect my CPU/Motherboard are now "toast".

In Windows 11 I "Shutdown" the computer not "Sleep" mode so I have no idea how or why or even when my PC decide to boot up by itself? I'll run the chiller on it for 30 minutes before trying to boot ... I'll check 'wake on LAN" option (if there is one) in the UEFI and see if it's default to "enable" which would be a CRAZY default not to mention huge security risk.

Can't tell you how angry I am right now ... $1800 worth of computer parts down the drain.

planetbeing
Level 7
So sorry to hear that. That sucks. My understanding is that most components will shut themselves down if they overheat so perhaps no permanent damage was done? By default, Power On By PCI-E (I think this controls wake-on-LAN) and Power On By RTC are disabled. It's possible that even in S4 or S5 (which Windows shutdown enters), USB might cause a wake, so maybe it was some misbehaving USB device. Perhaps in the future, you can enable ErP ready which will reduce power consumption at S4 and S5 and really prevent anything from turning the computer on. Is it possible that you set Restore AC Power Loss to "Power On" and an intermittent power loss event happened and ended up turning your computer on?

Also, why did you decide to put both SSDs in the Gen-Z.2?