PCIe bandwidth halved by connecting a second NVME SSD?
evening together,
Here is the following question for the experts among you:
I'd like to install another M2 SSD (currently only one is installed). However, I've heard that this would "steal" lanes (bandwidth) from the graphics card, resulting in poor performance since it has to share the connection with the NVME drive. Unfortunately, I couldn't find anything about this in the manual. My current SSD is a 1TB Kingston Fury Renegade (PCIe 4).
Graphics card: MSI RTX 4080 SUPRIM
Motherboard: MSI PRO Z790-A WIFI DDR4
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The impression can arise when one simplifies the actual facts of the simpler understanding because of so much that as well as everything relevant is omitted.
So, your processor can logically only have a limit number of internal peripheral devices manage. These include graphics cards, NVME disks, network chips, sound cards, etc., and they are all connected via different versions of PCIE interfaces. How to connect a graphics card via a PCIE x16 port and an NVME disk or a WLAN card usually via M.2.
However, as I said, the number lines , which are necessary to connect all these devices. And as board manufacturers want to give users as freedom as possible, more different connections are often installed than can be used at the same time. Then Share certain connections the lines, and depending on which "first" is connected to a device is then active, and the other has just bad luck.
Since as good as anyone in the top PCIE x16 slot installed a graphics card that really needs the full power of the slot, this slot never shares lines with another. As with your board as you can see here . If, for example, a PCIE x8 Slot Lanes splits with an M.2 slot, it would be noted with the corresponding slot.
I understand, thank you. So I could easily connect my NVME to any of the other slots without which they would share the Lanes. Since the GraKa already proves all her lanes anyway?
Or do I have a tunnel view somewhere?
Right. However, this is because your board does not have any slots that share lines.
As an example: At the ASUS x670e Pro Art Creator Board you have two split lines. This board has two PCIE x16 connectors, so you could theoretically connect two graphics cards. If only the upper slot is occupied, it can access the full 16 lines. If both are occupied, both have only access to 8 lines, since the upper slot divides 8 of its 16 lines with the lower one.
And in addition, another PCIE x4 connection is shared with one of the 4 M.2 connections on this board. Since all lines are divided here, only one of these connections can be used simultaneously.
As I said, this is not the case with your board.
I was already aware of that. Thought the division might be a standard at EATX. I don't know how I got it. Sometimes you think too complicated…
No, EATX is basically only the form factor, ie the size of the board. EATX is first identical to ATX, but ETAX is again to the right. How much varies from board to board. The board I mentioned actually also has ATX form factor.
You can usually find ETX boards in the workstation area, and the story with the lines works in a different way than on the desktop. It is simply because, on the one hand, the base itself is significantly larger in workstations, but in addition, many more voltage converters and RAM channels are installed, and this is often simply not enough.
Now I finally hated it:) very interesting, thank you again. To your example: is this not basically the case with E-ATX that the lines are split?