Help me understand this

[Isildur]

I'm looking at the Asus TUF Gaming B660m-Plus D4 and there are one thing i don't get:

 

On the specs of the mobo, on the expansion slots, it say:

Intel^® 12^th Gen Processors

1 x PCIe 5.0 x16 slot

Intel^® B660 Chipset*

1 x PCIe 3.0 x16 slot (supports x4 mode)

1 x PCIe 4.0 x1 slot

* Supports Intel^® Optane Memory H Series on PCH-attached PCIe slot.

 

What does it mean (supports x4 mode)? My best guess is that is a PCIe x 16, but it can also double for a x4 (hence the support). But, aren't PCie cross-compatible as well as backward compatible, as long as they are physically equal? Meaning that you can connect a x4 slot to a x16 slot? So, they are already "supported" for the get go. You can't

But in the overview it say something more:1x PCIe 3.0 x16 (PCH, at x4 mode).

From what i can understand it means that it will work as in 16 lanes, but only 4 lanes if in PCH. What is PCH and how is it relevant? Is it only relevant to Intel Optane, as descibed by the *?

[Guest]

4X mode is a short slotted card in a long PCI-E slot. You can use that slot for M.2 x4 expansion SSD in other words.

[Isildur]

19 hours ago, Guest 5150 said:

4X mode is a short slotted card in a long PCI-E slot. You can use that slot for M.2 x4 expansion SSD in other words.

So, if i understood correctly, i can use the PCIe slot with a 3.0 x 16 as normal, but if i connect an expansion card (m.2. or SATA) it turns to 4 lanes instead of the 16 (it can only be Gen 3 x 4 when it comes to MNVe expansion).

Is that it?

[Guest]

2 hours ago, Isildur said:

So, if i understood correctly, i can use the PCIe slot with a 3.0 x 16 as normal, but if i connect an expansion card (m.2. or SATA) it turns to 4 lanes instead of the 16 (it can only be Gen 3 x 4 when it comes to MNVe expansion).

Is that it?

Correct. Can use 3.0 4x cards, it will automatically detect the expansion card. But the second slot is only Gen 3.0 even with regular PCI-E cards.

[Isildur]

OK, thanks