Help me make sense of PCIe

[robby12312]

I'm considering buying a 1600X processor, GTX 1070, and an M.2 SSD.

My understanding from https://www.reddit.com/r/Amd/comments/6gy6yx/how_many_pcie_lanes_does_ryzen_have/ is that the 1600x has 24 usable PCIe lanes: 16 go to the GPU, 4 go to the NVME drive, 4 go to the chipset on the mobo. PCIe version what? Does it matter?

I look at a B350 mobo on https://www.newegg.com/Product/Product.aspx?Item=N82E16813144019&cm_re=b350-_-13-144-019-_-Product. here it sez i have a single PCI e.0 x16 slot. so this means my graphics card gets its full allotment of lanes going straight to the cpu.

it also says I have an M.2 slot that "Supports PCIe 3.0 x4 (RYZEN series processors) ". so my prospective M.2 https://www.newegg.com/Product/Product.aspx?Item=N82E16820147593&cm_re=m.2-_-20-147-593-_-Product gets it's full allotment of lanes straight to the cpu.

It has "2 x PCI Express 2.0 x1", so this means the mobo can physically give access to only 2 of the 4 lanes the cpu has allocated for the mobo chipset? Would a random Wi-fi card and bluetooth card get their full allocation directly to the mobo?

I plan on throwing in an SSD drive and 2,3 hard drives. the motherboard i'm looking at says it has "4 x SATA 6Gb/s". Are these independent of the PCIe lanes on the 1600x? or do they route in thru the 4 PCIe lanes allocated by the cpu to the chipset?

 

[raisonjohn]

There are PCIe lanes coming from BOTH the CPU (e.g. Ryzen 5 1600X) and the CHIPSET (e.g. B350).

You are correct that the 1600X (the CPU) has 24x PCIe lanes (version 3.0). In the MSI B350M Gaming Pro motherboard, the PCIe lanes controlled by the CPU is allocated by MSI as:
- 16x to the sole PCIe3.0 x16 slot
- 4x to the sole M.2 slot supporting PCIe3.0 x4 mode
- 4x to the media interface link (ver. 3.0) that is the bridge between the CPU and the Controller Hub (Chipset)

The last 4x PCIe lane used for CPU-Chipset communication is dedicated to such. Other PCIe lanes (version 2.0) usable by the motherboard's ports come from the Chipset (not the CPU):

For the B350 chipset, it has 6x PCIe lanes (version 2.0). The MSI B350M Gaming Pro motherboard distributes these PCIe lanes controlled by the Chipset as follows:
- 1x to the first PCIe2.0 x1 slot
- 1x to the second PCIe2.0 x1 slot
- 4x not used for this particular motherboard (to my knowledge)

The MSI B350M Gaming Pro motherboard's 4x SATA 6Gb/s ports are specifically independent of the PCIe lanes. So, you can plug SSD/HDD storage devices on all SATA ports and still be able to use the GPU's PCIe x16 slot at max. PCIe3.0 x16 speeds, the M.2 slot at max. PCIe3.0 x4 speeds, and the 2x PCIe2.0 x1 slots at max. PCIe2.0 x1 speeds.

The PCIe versions have different speeds:

PCIe3.0 x1 = ~1GB/s or ~8Gb/s (so, PCIe3.0 x16 = ~16GB/s or ~128Gb/s; and, PCIe3.0 x4 = ~4GB/s or ~32Gb/s)
PCIe2.0 x1 = 0.5GB/s or 4Gb/s (so, PCIe2.0 x16 = 8GB/s or 64Gb/s; and, PCIe2.0 x4 = 2GB/s or 16Gb/s)
*GB/s is Gigabytes per second; Gb/s is Gigabits per second

 

[robby12312]

There are PCIe lanes coming from BOTH the CPU (e.g. Ryzen 5 1600X) and the CHIPSET (e.g. B350).

You are correct that the 1600X (the CPU) has 24x PCIe lanes (version 3.0). In the MSI B350M Gaming Pro motherboard, the PCIe lanes controlled by the CPU is allocated by MSI as:
- 16x to the sole PCIe3.0 x16 slot
- 4x to the sole M.2 slot supporting PCIe3.0 x4 mode
- 4x to the media interface link (ver. 3.0) that is the bridge between the CPU and the Controller Hub (Chipset)

The last 4x PCIe lane used for CPU-Chipset communication is dedicated to such. Other PCIe lanes (version 2.0) usable by the motherboard's ports come from the Chipset (not the CPU):

For the B350 chipset, it has 6x PCIe lanes (version 2.0). The MSI B350M Gaming Pro motherboard distributes these PCIe lanes controlled by the Chipset as follows:
- 1x to the first PCIe2.0 x1 slot
- 1x to the second PCIe2.0 x1 slot
- 4x not used for this particular motherboard (to my knowledge)

The MSI B350M Gaming Pro motherboard's 4x SATA 6Gb/s ports are specifically independent of the PCIe lanes. So, you can plug SSD/HDD storage devices on all SATA ports and still be able to use the GPU's PCIe x16 slot at max. PCIe3.0 x16 speeds, the M.2 slot at max. PCIe3.0 x4 speeds, and the 2x PCIe2.0 x1 slots at max. PCIe2.0 x1 speeds.

The PCIe versions have different speeds:

PCIe3.0 x1 = ~1GB/s or ~8Gb/s (so, PCIe3.0 x16 = ~16GB/s or ~128Gb/s; and, PCIe3.0 x4 = ~4GB/s or ~32Gb/s)
PCIe2.0 x1 = 0.5GB/s or 4Gb/s (so, PCIe2.0 x16 = 8GB/s or 64Gb/s; and, PCIe2.0 x4 = 2GB/s or 16Gb/s)
*GB/s is Gigabytes per second; Gb/s is Gigabits per second

shocked and impressed at such a high quality answer. thank you very much for your help.

 

[Franklin_4]

following.