B560 motherboard with switchable M.2 Gen4 to Gen3

defoerate

defoerate

defoerate

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I got a really good price on a Intel 10400f CPU and I'm looking at buying a b560 motherboard.

Being a 10th gen CPU it only supports M.2 PCIe Gen3 but these motherboards come with Gen4.

I'm not sure if the B560 motherboards as standard allow switching the M.2 slot from Gen4 to Gen3?
 
Ok did a bit of research and it's definitely not a standard feature to be able to switch it.

MSI have a compatability chart (below) with 10th gen so for example the MORTAR's first slot (m2_1) can be switched to Gen3.

b560-20210330-1.jpg
 
PCIE Gen 4 is primarily a rocket lake feature on Intel B560. As far as I'm aware PCIE is fully backward compatible down to GEN2.
I'd be shocked if a PCIE GEN3 SSD didn't work when inserted into a GEN4 compatible slot.
 
Although not Intel I needed to make no changes putting a Gen 3 NVME into my X570 Tomahawk. As Cooler Running advises above they're backwards compatible and you shouldn't have any trouble or need to make any changes.
 
Cooler running said:
PCIE Gen 4 is primarily a rocket lake feature on Intel B560. As far as I'm aware PCIE is fully backward compatible down to GEN2.
I'd be shocked if a PCIE GEN3 SSD didn't work when inserted into a GEN4 compatible slot.
Click to expand...

Yeah but my understanding is since the 10400f doesn't support Gen4 it won't see any M.2 ssd (any gen) in the primary slot until I've switched in the bios to run at Gen 3. I could be wrong though.

MissChief said:
Although not Intel I needed to make no changes putting a Gen 3 NVME into my X570 Tomahawk. As Cooler Running advises above they're backwards compatible and you shouldn't have any trouble or need to make any changes.
Click to expand...

Yeah but your using a Ryzen 3000/5000 CPU which support up to Gen 4.
 
BallistixOnZ490 said:
You are wrong, a gen 3 will work but just not go up to gen 4 speeds.
Click to expand...

That's not what I'm saying, anyways I don't think I'm wrong you can read this on MSI's blog:

"Why M.2 slot is disabled with 10th Gen Intel Core Processor?
On Z590/B560 motherboards, the M.2 slot needs to be connected to the CPU to utilize the PCIe 4.0 x4 lanes from the 11th Gen Core Processor.

When the 10th Gen Intel Core Processor is installed, there are no PCIe 4.0 x4 lanes offered for M2. Slot. This is why the M.2 slot connected to the CPU is disabled with the 10th Gen Core Processor installed."
Click to expand...
 
BallistixOnZ490 said:
Ohhh, that I didn't know was even a thing!

So say if you wanted to get a Z590 and 10900K, the M.2 slot wouldn't work?
Click to expand...

Yeah fortunately MSI included a switch (on some mobo's) for the first M.2 slot to switch the connection between CPU and chipset so we can still use the slot at Gen3 speed.

BallistixOnZ490 said:
You would normally think it would still revert to 3.0 though.
Click to expand...

It would if you had an 11 series cpu.
 
defoerate said:
Yeah but my understanding is since the 10400f doesn't support Gen4 it won't see any M.2 ssd (any gen) in the primary slot until I've switched in the bios to run at Gen 3. I could be wrong though.
Click to expand...
PCIe devices always start communication at the slowest speed (+single lane) and bump up connection to higher speed (+higher lane count) only if both ends support it.
That's mandatory requirement of PCIe specification.
Only way for slot to stop working, is if CPU simply doesn't have those PCIe lanes.
(or wouln't be wonder if Intel has some cripple switch in BIOS to push people into 11th gen CPU)
 
defoerate said:
Yeah but my understanding is since the 10400f doesn't support Gen4 it won't see any M.2 ssd (any gen) in the primary slot until I've switched in the bios to run at Gen 3. I could be wrong though.
Click to expand...

10th gen not supporting gen 4 pcie isn't the problem here. It's that the 11th gen CPUs have an extra 4 lanes that can be used for a gen 4 slot, which 10th gen lacks.
The top gen 4 m.2 slot on a 500 series board is wired to use those 4 lanes from the cpu.

It looks like some board manufacturers have used some engineering tricks to use either use chipset lanes or cpu lanes for that slot depending on the cpu installed though.

With a lot of the boards, you can run another nvme drive off the chipset by using an adpater in the x4 lane pcie slot.

10th gen only has a x4 link to the chipset though, which may be a limitation when running multiple drives.
 
For some reason, ASRock B560M Steel Legend says that first slot can work with 10th gen (in PCIe 3.0 mode, ofc), which implies there's a switch like in MSI motherboards. If so, that probably makes it best buy B560 board because it's cheap (around 120€ for me), has decent VRM for B560 and it can boost the power limit for locked CPUs, both M.2 slots usable on 10th gen, it has diagnostic LEDs...
It's one of 4 mATX boards that allow 2 M.2 slots with 10th gen but it's much cheaper than Mortar, still cheaper (and a touch better) than Bazooka and it's straight up better than Pro-VDH. It's missing the back USB-C port, but for that price I can live with that. I may go and pair it with 10700F for some cheap 8-core powerhouse.

The ATX version of Steel Legend has 3 M.2 slots so even with first one disabled, you have 2 at your disposal. Same goes with every ATX B560 that has 3 M.2 slots, most likely (GB Aorus Pro, Asus Strix-F). There's a catch, though - on Steel Legend (ATX) the middle slot works in PCIe 3.0 x2 mode, not x4, most likely due to how PCIe slots are wired. The bottom one runs at full speed (so you want your best/boot drive in bottom slot on that board). Aorus Pro and Strix-F don't have that issue but they also cost a lot more. Oh, there's also the Asus TUF H570 Pro, I guess...
 
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Have been finding it hard to choose for same reason, it is tricky, especially as the primary / PCIe 4 slot is often much better placed. Not a fan of M.2 under the GPU. ASRock seem to have an edge on most others, with the functionality of their boards and it's nice to see some USB ports. 4 USB or nearly all USB 2.0 in 2021 is ridiculous :mad:
 
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