Question Populating both M.2 Slots

Dec 27, 2020
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Hi All, I am looking at a new build using an ASUS ROG Strix B550-I Gaming Mini-ITX board. Looking to run either a Ryzen 7 5800X or a Ryzen 9 5900X if I can ever find one. In any case my intent is to populate the top M.2 slot with a Sabrent Rocket 4.0 1TB NVME drive. As I understand it, the B550 spec allows for dedicated PCIE 4.0 lanes with this drive, which will not touch the 16 lanes for the GPU (allowing the GPU to run at x16 speeds). My question is this: the second (bottom) M.2 slot on the case is PCIE 3.0 and I would rather stick another drive in that slot instead of connecting a SATA SSD via the SATA interface. If I add the second M.2 drive (PCIE 3.0), will I be slowing down the GPU, i.e. will I be taking away dedicated lanes and forcing the GPU down to x8 speeds?

I've seen many threads saying things like "Even if the GPU drops to x8 you wouldn't really notice", which is not the point for me. This hardware isn't cheap, and I want it running at its maximum efficiency/capacity/speed whether I notice it or not. Otherwise it's kind of like saying "Well, your new Ferrari is limiting your acceleration, but it's already so fast, you really wouldn't notice it".

Any help is appreciated.
 
Hi All, I am looking at a new build using an ASUS ROG Strix B550-I Gaming Mini-ITX board. Looking to run either a Ryzen 7 5800X or a Ryzen 9 5900X if I can ever find one. In any case my intent is to populate the top M.2 slot with a Sabrent Rocket 4.0 1TB NVME drive. As I understand it, the B550 spec allows for dedicated PCIE 4.0 lanes with this drive, which will not touch the 16 lanes for the GPU (allowing the GPU to run at x16 speeds). My question is this: the second (bottom) M.2 slot on the case is PCIE 3.0 and I would rather stick another drive in that slot instead of connecting a SATA SSD via the SATA interface. If I add the second M.2 drive (PCIE 3.0), will I be slowing down the GPU, i.e. will I be taking away dedicated lanes and forcing the GPU down to x8 speeds?

I've seen many threads saying things like "Even if the GPU drops to x8 you wouldn't really notice", which is not the point for me. This hardware isn't cheap, and I want it running at its maximum efficiency/capacity/speed whether I notice it or not. Otherwise it's kind of like saying "Well, your new Ferrari is limiting your acceleration, but it's already so fast, you really wouldn't notice it".

Any help is appreciated.
The GPU and the top M.2 socket are fed directly by the CPU. The bottom M.2 socket is fed directly by the chip-set so using it will have no impact on either the GPU's lanes or the NVME's lanes in the top M.2.

Since it's a mini-ITX there are no other PCIe sockets to worry about lane sharing arrangements with them either. Although, I'm sure it has WiFi and healthy assortment of SATA and USB ports to compensate, and which will consume some PCIe lanes to function. But there are no strange sub-notes or asterisks to caution about lane stealing so it looks like Asus is just using what's available and leaving it at that.
 
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RealBeast

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. . . . If I add the second M.2 drive (PCIE 3.0), will I be slowing down the GPU, i.e. will I be taking away dedicated lanes and forcing the GPU down to x8 speeds? . . . .
No, the two GPUs with run at x16 while using two PCIe x4 NVMe drives. HERE is your motherboard manual that confirms it. The only issue is that the 1st GPU will not support PCIe 4.0 if you use an APU -- it runs at 3.0, which you are not.
 
Dec 27, 2020
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The GPU and the top M.2 socket are fed directly by the CPU. The bottom M.2 socket is fed directly by the chip-set so using it will have no impact on either the GPU's lanes or the NVME's lanes in the top M.2.

Since it's a mini-ITX there are no other PCIe sockets to worry about lane sharing arrangements with them either. Although, I'm sure it has WiFi and healthy assortment of SATA and USB ports to compensate, and which will consume some PCIe lanes to function. But there are no strange sub-notes or asterisks to caution about lane stealing so it looks like Asus is just using what's available and leaving it at that.
Hugely helpful, thank you. So, the next question would be, given that the bottom slot is only a PCIE 3.0 connection, should I bother with an NVME drive, or use a non-NVME drive? For that matter, should I just use a 2.5 inch SATA SSD on the 6gb/s SATA slots? I am trying to find that sweet spot of reduced cost on the second drive without sacrificing significant performance.
 

USAFRet

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Mar 16, 2013
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Hugely helpful, thank you. So, the next question would be, given that the bottom slot is only a PCIE 3.0 connection, should I bother with an NVME drive, or use a non-NVME drive? For that matter, should I just use a 2.5 inch SATA SSD on the 6gb/s SATA slots? I am trying to find that sweet spot of reduced cost on the second drive without sacrificing significant performance.
Given that this is a new build with 2x PCIe 3.0 capable M.2 ports, and given that M.2 NVMe drives are almost (but not quite) at parity with SATA III SSD of similar size, and given that this is a tiny system....there is little reason not to utilize both M.2 ports with relevant NVMe drives.
 
Hugely helpful, thank you. So, the next question would be, given that the bottom slot is only a PCIE 3.0 connection, should I bother with an NVME drive, or use a non-NVME drive? For that matter, should I just use a 2.5 inch SATA SSD on the 6gb/s SATA slots? I am trying to find that sweet spot of reduced cost on the second drive without sacrificing significant performance.
"only" PCie gen 3? that's still far faster data transfer than we typcically take advantage from. You'll probably not notice the difference between a good gen3 drive and the gen4 drive in typical desktop useage. But then, you'll probably not notice the difference between a PCIe gen3 NVME and a good SATA 6gb/s drive either. I don't appreciate the difference of the Gen 3 NVME and Gen 2 NVME I have in my system.

They all benefit mostly from the near instantaneous seek times of an SSD, the higher transfer rates matter when moving huge files. Windows doesn't operate that way, usually, and most app's don't either.

I'd still like using all NVME's in a mini-ITX build, though, as it can be extremely clean. No unecessary SATA power and data cables to muddle it up.
 

madmatt30

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Hugely helpful, thank you. So, the next question would be, given that the bottom slot is only a PCIE 3.0 connection, should I bother with an NVME drive, or use a non-NVME drive? For that matter, should I just use a 2.5 inch SATA SSD on the 6gb/s SATA slots? I am trying to find that sweet spot of reduced cost on the second drive without sacrificing significant performance.
Its still worth using a second nvme drive if ypu have the budget.

Most (if not all) of us are using nvme drives on pcie gen 3 slots.
They're still around 5 or 6 times faster than sata 3.

Its just probably not worth buying the fastest or most expensive drive for the secondary slot.
 

USAFRet

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Mar 16, 2013
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But then, you'll probably not notice the difference between a good PCIe gen3 NVME and a SATA 6gb/s drive either.
Exactly.

In my typical use case of Adobe Lightroom....
Intel 660p and 1 year old Samsung 860 EVO and 6 year old Samsung 840 EVO....I literally cannot tell the difference.
And I tested actual time it takes for a specific function.

15 secs = 15 secs = 15 secs.
Even though the Sequential benchmark numbers for the 660p are 3x that of the SATA III drives.

Most of what we (and Windows) do is NOT moving large sequential data around. And even then, the rest of the system comes into play.
 
Dec 27, 2020
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Thanks All! Sabrent Rocket 1TB NVME PCIE4.0 going into the top slot, and a Sabrent Rocket Q 2TB PCIE3x4 going into the bottom one! I am assuming that if I added an SSD on one of the SATA ports, that would also not rob performance?

Also managed to nab a 5900X from and an RTX 3070, and only overpaid by about $200 each, but I am proud that I didn't buy from scalpers!
 
.... I am assuming that if I added an SSD on one of the SATA ports, that would also not rob performance?

Also managed to nab a 5900X from and an RTX 3070, and only overpaid by about $200 each, but I am proud that I didn't buy from scalpers!
Installing that SATA SSD won't degrade performance of the system or the other drives in the least. Only it's own data transfers will be at lower SATA transfer speeds.

I had to give a sad laugh at that..."only overpaid by $200"... comment as I would consider that scalping still. But then, above-MSRP pricing has also become the norm now so I guess I can also see where you're coming from. I also have to imagine the only reason you could get a 3070 at all is because they're not (yet) being vacuumed up by miners.
 
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Dec 27, 2020
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Installing that SATA SSD won't degrade performance of the system or the other drives in the least. Only it's own data transfers will be at lower SATA transfer speeds.

I had to give a sad laugh at that..."only overpaid by $200"... comment as I would consider that scalping still. But then, above-MSRP pricing has also become the norm now so I guess I can also see where you're coming from. I also have to imagine the only reason you could get a 3070 at all is because they're not (yet) being vacuumed up by miners.
Thanks for the information. And re the overpayment, yes it's interesting except the scalping is now happening with the big resellers as well, not just some nobodies on Kijiji or eBay. And I saw that EVGA posted that they will be "adjusting" their pricing due to market demands. Crazy times.
 

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