Pcie and gen 4

Psycrow

Psycrow

Gawd
Joined
Feb 26, 2010
Messages
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I got a 3080 ti auros gigabyte gpu installed with a gen 4 cable and vertical bracket. So its gen 4 allright.
Now i got this motherboard ASUS ROG MAXIMUS XIII EXTREME - Z590 - LGA1200 and im using all 3 m.2 slots.
In the manual it states that using all 3 m.2 slots will decrease or somehow impact the gen 4 pcie.
But as i understand it now then my current card dosent use the max speed of the gen 4 anyway.
So the question is: Do i loose some of the speed or bandwidth when i install a 4090 gpu cuz im using all 3 m.2 slots ? Or wont a 4090 card benefit me anything regarding the pcie 4 ? Or will there be pcie 5 cables and does my motherboard support that ?
 
That motherboard actually supports five M.2 devices, not three. But it looks like the extra two need a proprietary "DIMM.2" module for them to be installed on.

According to page 13 of your manual:
https://dlcdnets.asus.com/pub/ASUS/...ME/E17684_ROG_MAXIMUS_XIII_EXTREME_UM_WEB.pdf

If you have M.2_1 and M.2_2 occupied, the first PCIe x16 slot drops to x8, and you lose the second PCIe x16 slot entirely. It doesn't specify anything about M.2_3, so there may be no penalty for using it. The additional DIMM.2 module for the extra M.2 slots starts to interfere with available SATA ports.

As for dropping your card from a full x16 to an x8 link, you will have performance loss. As to how much performance loss, it depends on the situation, but it generally isn't terrible. Where you really start to have steep performance loss is when going to anything less than x8, unless you have a lower end GPU that doesn't need a ton of bandwidth.
 
Yes there is a m.2 device that can hold 2 more so 5 total. And i installed 3 m.2 on all t emotherboards hidden sockets.

I dont use any sata so thats good.
hmm i should have installed the 2 m.2 on this dimm bracket rather than in the motherboards m.2 sockets...

I have a 3080 ti OC master extreme card.

Hmm i can ofc remove the 2 m.2 drives and install on the bracket when i installl the new 4090 card.

Does that dimm bracket support full speed for my samsung 980 pro m.2

So i remove the M.2_2 drive and install it in the Dimm bracket ?

DIMM.2_1 slot (Key M) via ROG DIMM.2, type 2242/2260/2280/22110 (supports
PCIe 3.0 x4 & SATA modes)

DIMM.2_2 slot (Key M) via ROG DIMM.2, type 2242/2260/2280/22110 (supports
PCIe 3.0 x4 mode)

DIMM.2_2 shares bandwidth with SATA6G_34 and DIMM.2_2 is default set at x2
mode.

If i use both sides of this dimm2 bracket. Will one of the drives only run 2 x speed?
 
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The manual is a bit ambiguous. It says the DIMM.2 slot operates in PCIe x2 mode if SATA ports 3 and 4 are enabled, which would imply that each M.2 slot only operates in x1 mode. If SATA 3 and 4 are disabled, it operates in x4 mode, which would imply that each M.2 slot operates in x2 mode.

If this is the case, then both M.2 slots operate at either half or a quarter of their maximum theoretical speed. It doesn't say whether using just one M.2 SSD will get all of the lanes, or if it's permanently shared with the other slot.
 
That seems strange...why would they let my 980 PRO PCle 4.0 NVMe™ M.2 SSD 1TB
Samsung down to half even with sata disabled.I dont have any sata installed.
The samsung is pcie 4.0 and the dimm bracket says pcie 3.0 x 4 So i wont get full speed for my M.2 drives using it.

So its either i loose drive speed or a bit of gpu speed.
I looked deeper in to this and it seems like pcie 4.0 x 8 is the same as pcie 3.0 x 16 and with my 3080 ti card then i would loose 1-2 % performance using all 3 motherboard M.2 slots.
I was just worried how much it would impact the 4090 card
 
There is so much bandwidth available in PCI 4.0 that your 4090 or any card will see minimal impact like single frame per second difference. Enjoy the technology without the worry.
 
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