[SOLVED] PCI 3.0 Riser Cable w/ PCI 4.0 M.2 SSD

[bsteinagel1]

Hello Everyone,

I would imagine this question has been answered before so apologies for asking again. Multiple searches on the forum weren't fruitful. I'm building a Ryzen 5900X system with an X570 motherboard--specifically the MSI X570S Carbon Max WiFi. I will be using the Fractal Flex B-20 riser bracket and cable in my build, which is a PCI 3.0 cable. My understanding is that for most stable performance the PCI slot for the GPU card should be set to PCI 3.0 mode. Will this throttle my 980 PRO SSD, a PCI 4.0 drive, down to PCI 3.0 as well? My understanding is that the X570 chipset allows for 20 PCI lanes off the CPU. Since the graphics card slot is x16 this should leave 4 extra lanes for the M.2 slot , in theory not affecting performance provided the M.2 slot can be treated separately from the PCI x16 slot. Can any one confirm this? Can the pci x16 slot be controlled independently of the M.2 slot?

Thank you in advance.

 

[USAFRet]

Why aren't you putting the 980 Pro in one of the M.2 ports?

 

[bsteinagel1]

I am. But the M.2 port also runs off the PCI bus, correct? That's why I'm wondering if dropping the graphics card slot to PCI 3.0 will affect the speed of the M.2 slot as well, or can the graphics card slot be dropped to PCI 3.0 while leaving the M.2 slot at full PCI 4.0 speed?

 

[--SID--]

The top M2 slot is directly wired to the CPU and don't share lanes with the top PCI-e x16 slot. All other M2 slots are wired to the chipset and has nothing to do with the upper PCI-e x16 slot.
This is what's happening when installing a M2 SSD

• 4x M.2 slots (Key M)
  • Supports PCIe 4.0 / PCIe 3.0
  • PCIe 4.0 is available only on AMD Ryzen™ 5000 Series and 3000 Series desktop processors
  • M2_1 (From processor)
    • Supports 2242/ 2260/2280/22110 storage devices
    • Supports up to SATA 6Gb/s
  • M2_2, M2_3 and M2_4 slots (from AMD X570 Chipset)
    • M2_2 & M2_4 slots support 2242/ 2260/ 2280 storage devices
    • M2_3 slot supports 2242/ 2260/2280/22110 storage devices
    • M2_2 & M2_3 slots support up to SATA 6Gb/s

• 
  
  • SATA5-6 will be unavailable when installing SATA SSD in the M2_3 slot; SATA5-8 will be unavailable when installing PCIe SSD in the M2_3 slot.
  
  
  • The PCI_E4 slot will be unavailable, when installing M.2 SSD into the M2_4 slot.

 

[bsteinagel1]

The top M2 slot is directly wired to the CPU and don't share lanes with the top PCI-e x16 slot. All other M2 slots are wired to the chipset and has nothing to do with the upper PCI-e x16 slot.
This is what's happening when installing a M2 SSD

• 4x M.2 slots (Key M)
  • Supports PCIe 4.0 / PCIe 3.0
  • PCIe 4.0 is available only on AMD Ryzen™ 5000 Series and 3000 Series desktop processors
  • M2_1 (From processor)
    • Supports 2242/ 2260/2280/22110 storage devices
    • Supports up to SATA 6Gb/s
  • M2_2, M2_3 and M2_4 slots (from AMD X570 Chipset)
    • M2_2 & M2_4 slots support 2242/ 2260/ 2280 storage devices
    • M2_3 slot supports 2242/ 2260/2280/22110 storage devices
    • M2_2 & M2_3 slots support up to SATA 6Gb/s

• 
  
  • SATA5-6 will be unavailable when installing SATA SSD in the M2_3 slot; SATA5-8 will be unavailable when installing PCIe SSD in the M2_3 slot.
  • The PCI_E4 slot will be unavailable, when installing M.2 SSD into the M2_4 slot.

Many thanks, SID, for the information. This is exactly what I was looking for!