[SOLVED] Appropriate M.2 expansion card on Z490 Tomahawk motherboard

Jul 30, 2020
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I just finished building a gaming PC with a Z490 Tomahawk motherboard. The onboard m.2 slots are already filled with a 1 TB and a .5 TB M.2 cards. My plan was to eventually add additional m.2 card(s) for video editing by adding an m.2 expansion card. I started researching M.2 expansion cards and the technical considerations are way over my head. I just learned about pcie lanes and that some pass through the cpu, or not, bifurcation, and 8 lanes being taken from the gpu, and I am totally lost.

In terms of compatibility, should I get a single, dual, or quad expansion card? Obviously I would like as many M.2 cards as possible (to setup some redundancy), but I don't want any problems with bandwidth if possible.
 

kanewolf

Titan
Moderator
I just finished building a gaming PC with a Z490 Tomahawk motherboard. The onboard m.2 slots are already filled with a 1 TB and a .5 TB M.2 cards. My plan was to eventually add additional m.2 card(s) for video editing by adding an m.2 expansion card. I started researching M.2 expansion cards and the technical considerations are way over my head. I just learned about pcie lanes and that some pass through the cpu, or not, bifurcation, and 8 lanes being taken from the gpu, and I am totally lost.

In terms of compatibility, should I get a single, dual, or quad expansion card? Obviously I would like as many M.2 cards as possible (to setup some redundancy), but I don't want any problems with bandwidth if possible.
Some of the concerns are not specific to an M.2 expansion card. ANY card you plug into the x16 slot, could force your graphics card to x8 mode. The good news is, that it really doesn't matter much. MOST graphics cards can't saturate an x8 PCIe 3.0 interface.
Then it is a question of how those x8 lanes are used. A dual slot card could use all 8 lanes. A quad card has to do something. It could run the slots as x2 or it could have a PCIe switch chip to allow the lanes to be shared.
 
Reactions: sotomo

kanewolf

Titan
Moderator
I just finished building a gaming PC with a Z490 Tomahawk motherboard. The onboard m.2 slots are already filled with a 1 TB and a .5 TB M.2 cards. My plan was to eventually add additional m.2 card(s) for video editing by adding an m.2 expansion card. I started researching M.2 expansion cards and the technical considerations are way over my head. I just learned about pcie lanes and that some pass through the cpu, or not, bifurcation, and 8 lanes being taken from the gpu, and I am totally lost.

In terms of compatibility, should I get a single, dual, or quad expansion card? Obviously I would like as many M.2 cards as possible (to setup some redundancy), but I don't want any problems with bandwidth if possible.
Some of the concerns are not specific to an M.2 expansion card. ANY card you plug into the x16 slot, could force your graphics card to x8 mode. The good news is, that it really doesn't matter much. MOST graphics cards can't saturate an x8 PCIe 3.0 interface.
Then it is a question of how those x8 lanes are used. A dual slot card could use all 8 lanes. A quad card has to do something. It could run the slots as x2 or it could have a PCIe switch chip to allow the lanes to be shared.
 
Reactions: sotomo
Jul 30, 2020
4
0
10
0
I just noticed that the second PCIe slot in my MB is only x4 speed even though it is x16 slot. Not sure if that matters. I think this looks nice but I do not see where to buy it. I'm wondering if it would be compatible.

So, I take it that x4 speed would mean that the bandwidth would need to be shared among multiple M.2s? Ok... yeah, I'm just now seeing that M.2 uses 4 lanes. So maybe I need to settle for just one if I want optimal speed. I plan to create a RAID of SATA drives for long term storage.
 

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