PCI-E Lanes, Zen 3, and B550

[Action_Johnson]

I've run out of USB ports on my desktop and looking into a PCI-E USB card I can use to plug in my X-56 and VR Headset. I'm not sure I have enough PCI-E lanes left for another add-in card without slowing down everything else though. I've got two add-in cards, and 3 hard drives taking up PCI-E bandwidth. It's my understanding that Zen 3 only has 24 lanes of PCI-E, and I'm pretty sure I'm maxed out. 

 

System is below:

 

AMD Ryzen 5 5600X

MSI B550 Tomahawk

32GB G.SKILL 3600 CL16 4x8GB

PowerColor Red Devil 5700XT

Creative Sound Blaster Z

WD Black SN850 500GB NVMe

WD Black SN750 2TB NVMe

WD Blue 1TB SATA SSD

 

 

[Firewrath9]

you can get a external usb hub for your non high bandwidth devices (mouse, keyboard, webcam, peripherals, etc.). any decent one off amazon should be fine.

[KrystianTheFox]

You can buy a USB expander like you plug one USB and you have 4 of them

[Fasauceome]

If you need more USB 3.0 ports AND all the bandwidth will be used at the same time for sure, you don't really have the chipset bandwidth for that.

 

But if you just need more ports for the occasional device, USB hubs or any old PCIe USB adapter will do.

[GuiltySpark_]

Yup, just get a quality hub. Done and done.

[mariushm]

The PROCESSOR has 24 pci-e lanes.

 

The CHIPSET creates additional pci-e lanes. For B550, that's 8 pci-e 3.0 lanes.

 

The processor also has a USB controller built in, and typically a few USB ports on the IO shield are connected directly to CPU

Other ports are from USB controller in chipset.

 

 

[Montana One-Six]

more info: https://www.gamersnexus.net/guides/3582-amd-chipset-differences-b550-vs-x570-b450-x470-zen-3

[Action_Johnson]

OK this helps. If I'm reading that chart right, it looks like I'm already beyond maxing out the boards bandwidth considering I'm running 2 NVMe's, a SATA drive, GPU, and a sound card. 

 

On the chart, I don't know what 2x2 NVMe means, I guess that's two NVMe drives, running at 2x?

By running an SN850 + SN750 in the Gen 4 and Gen 3 slots respectively, am I only getting PCI-E 2x out of them? By using the slots available on the board, am I seriously making it slower? That's pretty bullshit to put a bunch of slots on a motherboard if it drags the whole system down. I really hope I'm reading that incorrectly. 

 

I'm concerned about using a hub because the X56 is super power hungry, and is documented to have trouble with hubs, even powered ones. Also, the VR Headset is is pretty buggy, most of the time I connect it, WMR gives me an error code and I hear the buh-dink chime of it connecting/disconnecting. After 1-3 reboots, it'll connect and stay connected.

 

My mouse and keyboard go on the two USB 2.0 ports, so by putting those onto a hub, I'm not going to really net anything useful. I guess I can try to put the Odyssey+ and the X56 on a powered USB-C Hub, but I'm skeptical of it working. 

 

 

[mariushm]

29 minutes ago, Action_Johnson said:

On the chart, I don't know what 2x2 NVMe means, I guess that's two NVMe drives, running at 2x?

The chart tries to tell you about POSSIBILITIES , OPTIONS.

 

It wants to say that 4 pci-e lanes are "recommended", (it's AMD's desire you should use them for that) for a M.2 connector.

BUT, the motherboard manufacturer has the OPTION of connecting all 4 pci-e lanes to a single M.2 connector, or they can put 2 M.2 connectors and connect 2 pci-e lanes to each one, or they can lose 2 pci-e lanes but gain 2 sata ports.

That refers strictly to the 4 pci-e lanes coming from CPU. 

Pretty much all motherboards route all 4 pci-e lanes to a single M.2 connector, so there's only one M.2 connector linked directly to CPU. The other m.2 connectors, are usually connected to chipset, with very few exceptions (like that gigabyte board I mentioned which takes 8 pci-e lanes from the 16 dedicated to video cards and splits them in 2 x4 groups for 2 extra m.2 connectors connected to cpu directly)

 

You can see in chart it says "Pick one" ... that means motherboard maker can pick one of those possibilities.

1. use all 4 pci-e lanes to the m.2 connector

2. enable 2 extra sata connectors but lose 2 pci-e lanes, so the m.2 connector will have only 2 pci-e lanes.

3. use all 4 pci-e lanes for m.2 connectors, but split them in 2 to create 2 m.2 connectors "powered" by cpu pci-e lanes.

 

36 minutes ago, Action_Johnson said:

By running an SN850 + SN750 in the Gen 4 and Gen 3 slots respectively, am I only getting PCI-E 2x out of them? By using the slots available on the board, am I seriously making it slower? That's pretty bullshit to put a bunch of slots on a motherboard if it drags the whole system down. I really hope I'm reading that incorrectly. 

 

Of course it's incorrect.

Your motherboard manufacturer chose OPTION 1. Use all 4 pci-e lanes coming from CPU to connect the first m.2 connector directly to CPU.

The 2nd m.2 connector uses 4 of the 8 pci-e lanes the chipset creates (see chart, the right side) to implement a 2nd m.2 connector.

So both m.2 SSDs will run at maximum speed and bandwidth.

 

[Action_Johnson]

40 minutes ago, mariushm said:

The chart tries to tell you about POSSIBILITIES , OPTIONS.

 

It wants to say that 4 pci-e lanes are "recommended", (it's AMD's desire you should use them for that) for a M.2 connector.

BUT, the motherboard manufacturer has the OPTION of connecting all 4 pci-e lanes to a single M.2 connector, or they can put 2 M.2 connectors and connect 2 pci-e lanes to each one, or they can lose 2 pci-e lanes but gain 2 sata ports.

That refers strictly to the 4 pci-e lanes coming from CPU. 

Pretty much all motherboards route all 4 pci-e lanes to a single M.2 connector, so there's only one M.2 connector linked directly to CPU. The other m.2 connectors, are usually connected to chipset, with very few exceptions (like that gigabyte board I mentioned which takes 8 pci-e lanes from the 16 dedicated to video cards and splits them in 2 x4 groups for 2 extra m.2 connectors connected to cpu directly)

 

You can see in chart it says "Pick one" ... that means motherboard maker can pick one of those possibilities.

1. use all 4 pci-e lanes to the m.2 connector

2. enable 2 extra sata connectors but lose 2 pci-e lanes, so the m.2 connector will have only 2 pci-e lanes.

3. use all 4 pci-e lanes for m.2 connectors, but split them in 2 to create 2 m.2 connectors "powered" by cpu pci-e lanes.

 

 

Of course it's incorrect.

Your motherboard manufacturer chose OPTION 1. Use all 4 pci-e lanes coming from CPU to connect the first m.2 connector directly to CPU.

The 2nd m.2 connector uses 4 of the 8 pci-e lanes the chipset creates (see chart, the right side) to implement a 2nd m.2 connector.

So both m.2 SSDs will run at maximum speed and bandwidth.

 

OK thank god. Well I'm going to use one of the on-board USB headers on the motherboard, and see if that helps. I've got two headers open, and only one PCI-E slot unused, and as much as I love seeing a computer filled with add-in cards (I'm old), using existing headers might be the way to go. 

[Action_Johnson]

52 minutes ago, mariushm said:

The chart tries to tell you about POSSIBILITIES , OPTIONS.

 

It wants to say that 4 pci-e lanes are "recommended", (it's AMD's desire you should use them for that) for a M.2 connector.

BUT, the motherboard manufacturer has the OPTION of connecting all 4 pci-e lanes to a single M.2 connector, or they can put 2 M.2 connectors and connect 2 pci-e lanes to each one, or they can lose 2 pci-e lanes but gain 2 sata ports.

That refers strictly to the 4 pci-e lanes coming from CPU. 

Pretty much all motherboards route all 4 pci-e lanes to a single M.2 connector, so there's only one M.2 connector linked directly to CPU. The other m.2 connectors, are usually connected to chipset, with very few exceptions (like that gigabyte board I mentioned which takes 8 pci-e lanes from the 16 dedicated to video cards and splits them in 2 x4 groups for 2 extra m.2 connectors connected to cpu directly)

 

You can see in chart it says "Pick one" ... that means motherboard maker can pick one of those possibilities.

1. use all 4 pci-e lanes to the m.2 connector

2. enable 2 extra sata connectors but lose 2 pci-e lanes, so the m.2 connector will have only 2 pci-e lanes.

3. use all 4 pci-e lanes for m.2 connectors, but split them in 2 to create 2 m.2 connectors "powered" by cpu pci-e lanes.

 

 

Of course it's incorrect.

Your motherboard manufacturer chose OPTION 1. Use all 4 pci-e lanes coming from CPU to connect the first m.2 connector directly to CPU.

The 2nd m.2 connector uses 4 of the 8 pci-e lanes the chipset creates (see chart, the right side) to implement a 2nd m.2 connector.

So both m.2 SSDs will run at maximum speed and bandwidth.

 

I found this diagram in my motherboard's manual, MUCH more helpful than the weird graphic AMD made