What does it mean? "When M.2_2 slot is populated, SATA6G_56 will be disabled."

[Sen7a]

Hello guys. When i review new B550 motherboards. Almost all of them using this footnote* I understand what does it mean. So even if your mobo has 6 sata port. you cant use some of them together with m2 ssd. So if i have 6 drive(2 M2 SSD and 2 SATA SSD and 2 HDD for exmaple) i can use them full performance because of that. Am i understand correctly?

My question is more deeply. Why this is happening? When i search throug internet PCIe and SATA they are different right. OR are not really different. Why my SATA port disabled from x4 PCIe lane. Is SATA ports hasnt their lanes? I want to understand what is going on inside motherboards or chipsets. Where can i find more detailed explanation. I cant find it in amd's or mainstream mobos company's websites.

 

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[Skiiwee29]

If you look at the picture, it means that if you have an m.2 installed in the bottom m.2 slot, marked B, it will disable the 2 Sata ports also labeled B just above it. 

[minibois]

Just now, Sen7a said:

I understand what does it mean. So even if your mobo has 6 sata port. you cant use some of them together with m2 ssd.

So if i have 6 drive(2 M2 SSD and 2 SATA SSD and 2 HDD for exmaple) i can use them full performance because of that. Am i understand correctly?

Yes, you're understanding that correctly. Just make sure the two SATA SSD's and two SATA HDD's aren't on ports 5 and 6.

1 minute ago, Sen7a said:

My question is more deeply. Why this is happening? When i search throug internet PCIe and SATA they are different right. OR are not really different. Why my SATA port disabled from x4 PCIe lane. Is SATA ports hasnt their lanes?

It has to do with the input and output lanes of the CPU and chipset.

SATA and PCIE are indeed two seperate type of signals, but in the design of the chipset (because the lower M.2 is routed through the chipset to the CPU) only allows for so many connections and they choose to route the M.2_2 and SATA 5/6 on the same lane, meaning you can only use one or another.

3 minutes ago, Sen7a said:

I want to understand what is going on inside motherboards or chipsets. Where can i find more detailed explanation. I cant find it in amd's or mainstream mobos company's websites.

Unfortunately this isn't very public information, but if you want to get more info on this, look up the blockchart or blockdiagram of different chipsets to get an idea of how they decide to route stuff.

Here is a review from KitGuru: https://www.kitguru.net/components/motherboard/ryan-martin/asus-rog-strix-b450-i-gaming-motherboard-review/3/

That goes over B450's blockdiagram:

Spoiler

As you can see on the topleft, the PCIE x16 slots shares a lane with the M.2_2 slot, meaning those are shared.

[Sen7a]

3 minutes ago, Skiiwee29 said:

If you look at the picture, it means that if you have an m.2 installed in the bottom m.2 slot, marked B, it will disable the 2 Sata ports also labeled B just above it. 

Did you read second part of question? it was below the image maybe you missed. i edited again

[Sen7a]

4 minutes ago, minibois said:

As you can see on the topleft, the PCIE x16 slots shares a lane with the M.2_2 slot, meaning those are shared.

So when using x16 slot together m2 slot, x16 will be reduce to x8 again right ? So this cpu lane only allow x16 but sum of x16 gpu and x4 m2 is x20.there is no x20 lanes so they will reduce x16 to x8 so on x8 + x4 will work together properly?

[minibois]

2 minutes ago, Sen7a said:

So when using x16 slot together m2 slot, x16 will be reduce to x8 again right ? So this cpu lane only allow x16 but sum of x16 gpu and x4 m2 is x20.there is no x20 lanes so they will reduce x16 to x8 so on x8 + x4 will work together properly?

That was a B450 example, as I couldn't find such a blockdiagram for B550.

I don't think that exact example is the case with B550, as the top PCIE slot is seperate from everything else and will just run at x16 speeds.

The bottom PCIE x16 slot does share bandwidth with other PCIE slot, as can be seen in the screenshot you posted above.

[Sen7a]

i said that for b450. i did some math for that.

Ofc B550's top PCIe slot and top M2 slot are seperated. Thanks