Why MSI did this in the B450

[Coolday]

I have the board MSI B450 Pro gaming carbon AC and I choose it so I can install 2 nvme later but I found that if I used the second nvme all the PCIE gets disabled except one !! I checked same boards B450 from Asus and gigabyte and I did not find them doing the same so why MSI is limiting this board like this ? if I would noticed this I would choose another brand.

[kirashi]

11 minutes ago, Coolday said:

why MSI is limiting this board like this

Um, it's not just MSI that does this on some boards -- all manufacturers have motherboards in their lineup which have limitations on the PCIe lanes depending on what you install in the M.2 slots. This is prominently listed on the manufacturer website, too, so you really need to do your research before blaming a company for something that was outlined on their website. Click on the Detail tab on the following specification page for that motherboard.

 

https://www.msi.com/Motherboard/B450-GAMING-PRO-CARBON-AC/Specification

 

[Coolday]

12 minutes ago, kirashi said:

Um, it's not just MSI that does this on some boards -- all manufacturers have motherboards in their lineup which have limitations on the PCIe lanes depending on what you install in the M.2 slots. This is prominently listed on the manufacturer website, too, so you really need to do your research before blaming a company for something that was outlined on their website. Click on the Detail tab on the following specification page for that motherboard.

 

https://www.msi.com/Motherboard/B450-GAMING-PRO-CARBON-AC/Specification

 

 

This is not true . I said in the post that other B450 boards does not has same severe limitation. You just said the info I already know or you just dont know like me why MSI did this ?

[kirashi]

Just now, Coolday said:

I said in the post that other B450 boards does not has same sever limitation. 

OK, and I said "it's not just MSI that does this on some boards -- all manufacturers have motherboards in their lineup which have limitations on the PCIe lanes...." Please note the word some - not all boards will have this limitation. Usually, the more expensive boards have the ability to populate all their M.2 slots with PCIe NVMe drives and still have enough PCIe lanes to run all their SATA ports, too. You just have to do the research to find out which ones support this.

[Coolday]

No I found same price with also little cheaper boards does not has this limitation like Asus strix B450 and Aorus B450 Elite. 

[germs]

@kirashi is right

 

but i believe this is due to the chipset limitation

 

- the first nvme drive is handled by the cpu -- via a pcie lane split by a "switch" -- on this "switch", you have the primary nvme (m2_1) socket and 2 sata ports (sata5 and sata6 in your case)

- the second nvme is handled by the chipset -- similar as above, the secondary nvme (m2_2 slot) and 4 pcie slots are split

 

i dunno how these "switches" work exactly, either yes or no lol can't do both

[germs]

1 minute ago, germs said:

@kirashi is right

 

but i believe this is due to the chipset limitation

 

- the first nvme drive is handled by the cpu -- via a pcie lane split by a "switch" -- on this "switch", you have the primary nvme (m2_1) socket and 2 sata ports (sata5 and sata6 in your case)

- the second nvme is handled by the chipset -- similar as above, the secondary nvme (m2_2 slot) and 4 pcie slots are split

 

i dunno how these "switches" work exactly, either yes or no lol can't do both

let me rephrase, not chipset limitation, but limitation on how the chipset is implemented 

[Coolday]

1 minute ago, germs said:

let me rephrase, not chipset limitation, but limitation on how the chipset is implemented 

In other words MSI has "less efficient" implementation than other companies ?

[germs]

3 minutes ago, Coolday said:

In other words MSI has "less efficient" implementation than other companies ?

i would be surprised if this is implemented differently on other brands, a chipset is a chipset, they all have their own "mix" of features but of course with its limitations!

 

i'm looking at the asus b450 plus mobo, they mention the same thing : 

 

 

from : https://dlcdnets.asus.com/pub/ASUS/mb/SocketAM4/PRIME_B450-PLUS/E14214_PRIME_B450-PLUS_UM_WEB_060418.pdf

 

this mobo (asus b450 plus)  only has one nvme socket, coming from the cpu -- similar to your case, when that is plugged in, 2 sata ports sharing the same lanes is disabled

 

(no secondary nvme socket, so the other pcie sockets are not constrained by this limitation)

 

am i making sense? lol

[Jurrunio]

The Aorus Elite anyway disables 2 extra SATA ports when the second M.2 slot is occupied while the Asus B450-F drops PCIe speed of the top slot from x16 to x8 (tho it supports PCIe 3.0 x4 SSDs in the second M.2 slot while the other 2 drops to PCIe 2.0 x4 and 3.0 x2). In other words when the Carbon, B450-F and Elite both have 2 M.2 SSDs, Carbon gives you only 1 PCIe x16 slot and 4 SATA, B450-F gives you more PCIe but x8 for the graphics card while Elite gives you more PCIe but only 2 SATA. This is not a "this vendor better than the other vendor", but a matter of "where do they get the needed lanes". If you want more I/O, pay more for X470. That's product segmentation from AMD, handled differently by different vendors.

 

The Carbon also has the best power delivery.

[Coolday]

Thanks guys