Question PCIe 5.0 lanes question

[TheFabled]

In a few days I will build my new PC.

MSI Z790 Carbon WiFi
I7-13700k 3.4ghz
Kingston gen4 2TB 7000mb/sec nvme
ASUS RTX 4090 TUF
64 GB DDR5 6000MHZ.

The nvme slot called M2_2 beneath the top slot and right above the pci express 5.0 graphics card slot, share bandwidth. And i was considering inserting the Kingston nvme drive in that slot.

Will there be any bandwidth issue for either the 4090 or the gen4 nvme in this setup or will they both work at full speeds?

If so. Hypothetically, if I choose to buy a gen5 nvme in the future to insert in that slot? what then?

Or maybe just insert the gen4 nvme in M2_3, M2_4 or M2_5 under the large cover instead. Or Shoulder the Main nvme system drive go through CPU and not Chipset?

And lastly. One of my other nvme drives are the corsair MP600 gen3 2TB that comes with it's own massive heatsink. Inserting that in any if the bottom 3 slots with that sink would make it impossible to re attach the motherboard shield. Anyone know if the motherboard shield is good enough for the mp600?

If not, I need to put the mp600 in either m2_1 or m2_2.


I just want everything to run at it's full potential.

 

[boju]

Looking at your motherboard specs it says 2nd m2 is pcie 5 from cpu. It's known pcie 5 ssds reduces gpu lanes to 8x but there's no reference of that happening here with your board, probably was a limitation to 6xx series. Your board doesn't mention such limitation.

Refer to the motherboard manual as well and that huge plastic cover you're referring to that i gathered isn't just plastic but heatsinks for various aspects of the motherboard. Read the manual.

 

[TheFabled]

Looking at your motherboard specs it says 2nd m2 is pcie 5 from cpu. It's known pcie 5 ssds reduces gpu lanes to 8x but there's no reference of that happening here with your board, probably was a limitation to 6xx series. Your board doesn't mention such limitation.

Refer to the motherboard manual as well and that huge plastic cover you're referring to that i gathered isn't just plastic but heatsinks for various aspects of the motherboard. Read the manual.

Thank you.
Yeah, I might have confused that with the manual of the Tomahawk wifi which i also considered buying.

When it comes to lanes and full potentials and so on. I feel I might miss out on Important information, even if I read the manual. So I ask questions on subjects I'm not sure about.

 

[SkyNetRising]

I just want everything to run at it's full potential.

1. You should not use M2_2 slot at all, if there are other free M.2 slots available.
Because using this slot will cut PCIE_x16 slot bandwidth in half.
2. Main OS drive should go into CPU connected M2_1 slot.
3. Motherboard heatsink should be enough for MP600.
Just watch some videos, how to remove MP600 heatsink without causing any damage.

 

[boju]

1. You should not use M2_2 slot at all, if there are other free M.2 slots available.

First m2 slot is designated as pcie 4, second m2 as pcie 5. It's backwards but it's how im reading specifications 🤔

 

[Zerk2012]

You should be able to use either the m.2 slot 1 or 2 but not both in theory since they both run off the CPU lanes and the CPU only has 20 lanes.

On slot 2 it says.
*PCI_E1 slot will be Gen5x8 when installing M.2 SSD in the M2_2 slot.
The way that reads it's saying not to use it but I have no clue why it would cut it down to X8 when it's still only using 4 lanes if the M.2 slot 1 is not used.

You can always try it and see if using only slot 2 it cuts down to X8 for the video card.

 

[TheFabled]

First m2 slot is designated as pcie 4, second m2 as pcie 5.

Yes. This is also why i have these questions because i don't fully understand the lanes and stuff. The RTX 4090 is Gen4, not Gen5. The nvme is also Gen4, not gen 5. But, Gen5 has double the bandwith as gen4. So would it even matter if i have two gen4 products added here? They are not designed to utilize gen5 speeds anyways.

I have also now read the manual again, and it says this: "PCI_E1 will operate x8 speed when installing M.2 PCIe SSD in the M2_2 slot."

It does say operate at x8, that means same speed as x16 gen4 right? It's that simple? There is no other trickery involved?

I then also would assume that the gen4 m2 also gets gen5 x8, which is same as gen4 x16.?

 

[SkyNetRising]

It does say operate at x8, that means same speed as x16 gen4 right? It's that simple? There is no other trickery involved?

Since your device (graphics card) is PCIE 4.0, then slot switching into x8 mode, you get PCIE 4.0 x8 mode.
PCIE 4.0 card can not operate in PCIE 5.0 mode.

I then also would assume that the gen4 m2 also gets gen5 x8, which is same as gen4 x16.?

M.2 slot operates in x4 mode - either PCIE 5.0 or PCIE 4.0 or PCIE 3.0 (depending on supported mode of specific drive).

 

[TheFabled]

Since your device (graphics card) is PCIE 4.0, then slot switching into x8 mode, you get PCIE 4.0 x8 mode.
PCIE 4.0 card can not operate in PCIE 5.0 mode.

M.2 slot operates in x4 mode - either PCIE 5.0 or PCIE 4.0 or PCIE 3.0 (depending on supported mode of specific drive).

Oh snap. Yea this is what i feared, this lane stuff makes my brain melt. This means i will lose about 3% of the performance on the 4090, as i have figured after googling a little bit, X8 in Gen4 is about 3% of X16 on that card it seems. Maybe not a big deal, but since this is a 5000$ PC, I'd like every little inch of juice rendered on my monitor.

The system disk. Which is a Gen4 Kingston Fury Renegade M2. I might need to add that to M2_1 then. But, would also love to have the Corsair MP600 there because it comes with it's own huge heat sink.
Not a deal breaker though.

But running the system disk through the chipset (M2_3, M2_4 or M2_5), is this a non issue, or should the system disk always go directly through the CPU?

And then when it comes to directstorage, does that work through both cpu and chipset nvme's?

 

[SkyNetRising]

But running the system disk through the chipset (M2_3, M2_4 or M2_5), is this a non issue, or should the system disk always go directly through the CPU?

System NVME drive should be cpu connected.
Chipset connected drives will incur performance penalty.

 

[TheFabled]

System NVME drive should be cpu connected.
Chipset connected drives will incur performance penalty.

Alright thank you. I should've bought a 4TB drive for that slot, and ran my games on it as well. *Sigh*
well then it seems i have to add the kingston to M2_1, and then the MP600 in M2_3 or something, i then need to remove that huge heat sink on it.

But DirectStorage works through chipset right?

 

[hotaru.hino]

But DirectStorage works through chipset right?

Yes, but before we get all panicking about storage performance, here's some considerations:

• Storage performance isn't really a factor once the application has loaded everything it needs into RAM, which is usually the initial load. If you're playing some sort of twitch shooting game like Call of Duty or CS:GO, then they're going to basically load everything it needs in RAM
• Even if you're playing something like open world games, most of them are designed in such a way to soften the need for bandwidth performance by doing things like caching ahead if the game thinks you're heading in a certain direction or loading the bare minimum that's required, keeping that in RAM, and loading everything else as needed over time since chances are you're not going to be flinging around the map at a supersonic speed
• Until we have more DirectStorage games, which I think there's only like one right now and even using DirectStorage only offers something like <3% better performance in loading, I don't think it's worth worrying about it.

As much as I understand you want the absolute best performance or a "no compromises" build, the fact is, you can't have this, especially with consumer grade stuff.

 

[Deleted member 2838871]

As much as I understand you want the absolute best performance or a "no compromises" build, the fact is, you can't have this, especially with consumer grade stuff.

Yep... I understand the OP's excitement in a new build... I was just there myself. Still... OP is definitely overthinking this. PCIE 5.0 isn't even an option on GPUs and is complete and total overkill on SSDs.

 

[TheFabled]

Yep... I understand the OP's excitement in a new build... I was just there myself. Still... OP is definitely overthinking this. PCIE 5.0 isn't even an option on GPUs and is complete and total overkill on SSDs.

Wait what?Now i became confused again.
I have stated myself that i know this for a fact, the problem is the lanes.

By cutting the lanes in half on v5, you also cut them in half on v4.
Meaning that if i add an M2 to that slot, it means my RTX 4090 will only have bandwith equal to Gen4 x8, not Gen4 x16 which i hoped it would.

That actually means the RTX 4090 will in fact take a performance hit, not a huge one as far as i have managed to gather, but a performance loss none the less.

If the lanes had worked dfferently on the other hand, that x8 lanes on Gen5 had equalled x16 lanes on Gen4, it would not have been a problem. So i am well aware that either my GFX card or my M2 is Gen5, as i have already stated in my original post.

 

[TheFabled]

Yes, but before we get all panicking about storage performance, here's some considerations:

• Storage performance isn't really a factor once the application has loaded everything it needs into RAM, which is usually the initial load. If you're playing some sort of twitch shooting game like Call of Duty or CS:GO, then they're going to basically load everything it needs in RAM
• Even if you're playing something like open world games, most of them are designed in such a way to soften the need for bandwidth performance by doing things like caching ahead if the game thinks you're heading in a certain direction or loading the bare minimum that's required, keeping that in RAM, and loading everything else as needed over time since chances are you're not going to be flinging around the map at a supersonic speed
• Until we have more DirectStorage games, which I think there's only like one right now and even using DirectStorage only offers something like <3% better performance in loading, I don't think it's worth worrying about it.

As much as I understand you want the absolute best performance or a "no compromises" build, the fact is, you can't have this, especially with consumer grade stuff.

Yes I'm well aware that that not many games utilize this yet. But yes the games are coming and this PC is built as a powerhouse to last 4-5 years maybe. I just don't want to have this expensive PC and build it wrong in some way, i just want to avoid any bottle neck if i can.

And i skipped on the I9-13900k and 4090 OC, because in my opinion you get a maybe 5% boost combined doing that, but the power draw is just so much higher. So i didn't really think it was worth it. I try to be somewhat reasonable. 😆

But anyways, thanks for your reply, it seems i have gotten it right now. I even swapped the Kingston Fury 2TB with a 4TB so i can have my installed games on that in M2_1 slot instead of on the MP600 in M2_3. 😊

 

[Deleted member 2838871]

By cutting the lanes in half on v5, you also cut them in half on v4.
Meaning that if i add an M2 to that slot, it means my RTX 4090 will only have bandwith equal to Gen4 x8, not Gen4 x16 which i hoped it would.

The whole thread is confusing me... I'm a big believer in MSI boards... used them for years. I don't think I would have went the route you went though. Adding an m.2 will gimp your GPU? No thanks.

The only shared bandwidth issues my MSI board offers is if I use the 4th m.2 slot (which I have, all 4 are populated) that it will share bandwidth with the lowest PCIe slot. A minor issue that I don't have to worry about because my devices are using other PCIe slots.

Maybe you bought the wrong board?

Good luck.

P.S.

Even with the minor gimpage of your 4090 you aren't going to notice it... its a beast of a card.

Yes I'm well aware that that not many games utilize this yet. But yes the games are coming and this PC is built as a powerhouse to last 4-5 years maybe. I just don't want to have this expensive PC and build it wrong in some way, i just want to avoid any bottle neck if i can.

This is what I'm talking about when I said you were overthinking it. You built a 13700k PC with a 4090 and you're worried about "bottlenecks?"

 

[TheFabled]

The whole thread is confusing me... I'm a big believer in MSI boards... used them for years. I don't think I would have went the route you went though. Adding an m.2 will gimp your GPU? No thanks.

The only shared bandwidth issues my MSI board offers is if I use the 4th m.2 slot (which I have, all 4 are populated) that it will share bandwidth with the lowest PCIe slot. A minor issue that I don't have to worry about because my devices are using other PCIe slots.

Maybe you bought the wrong board?

Good luck.

P.S.

Even with the minor gimpage of your 4090 you aren't going to notice it... its a beast of a card.



This is what I'm talking about when I said you were overthinking it. You built a 13700k PC with a 4090 and you're worried about "bottlenecks?"

hehe. Well the 13700k had the exact same amount of performance cores as the 13900k. I haven't really watched detailed analysis and testing comparing all this stuff against one another, with higher speed ram and so on.

When i talk about bottle neck in my case, is that if i have something that can perform a certain way, and i have mounted it wrong, causing it to underperform, that is the bottle neck I'm talking about.

I'm well aware of the performance that each of these components are capable of.
And yes, well, i was considering the ASUS ROG Maximus HERO which also has built in thunderbolt 4 ports. But
it also costs 250$ more than the Carbon, and only have three M.2 slots on the MB (the last two on a PCI express card). compared to the carbon's five slots on the MB.

But i don't need all 5 slots all the time, i will use the M2_2 slot only when i need to add a new M2 for some copy paste for example. But for long term, i will just use the M2_1, which doesn't affect the lanes on the PCIE_1.

7000MB sec is really fast. I don't think i will really need a Gen5 nvme anytime soon

And also, If i decide to buy the RTX 5090 nest year. i now have a motherboard that supports PCIe Gen5.

 

[Deleted member 2838871]

7000MB sec is really fast. I don't think i will really need a Gen5 nvme anytime soon

Neither will I.

As for the 5090... I don't see it being necessary at least for my use case. When the 4090 doesn't even break a sweat at running 4K Ultra 60 fps with RT on... I don't have a need for a 5090.

Good luck with the build!

 

[TheFabled]

Neither will I.

As for the 5090... I don't see it being necessary at least for my use case. When the 4090 doesn't even break a sweat at running 4K Ultra 60 fps with RT on... I don't have a need for a 5090.

Good luck with the build!

Yes thanks. Let's hope i don't need a new PC for a few years. 😁👍