Friday, May 15th 2020
GIGABYTE B550 AORUS Master Waltzes Around Chipset Limitations to Provide Three Gen 4 M.2 Slots
GIGABYTE B550 AORUS Master is the company's most premium socket AM4 motherboard based on the upcoming AMD B550 chipset. We described this board in some detail in our older article covering an assortment of top B550 motherboards from manufacturers, but missed a key bit. At the time we assumed that the PCI-Express lane switches located below the board's main PCI-Express slot merely split its x16 connection from the AM4 SoC down to two x8 connections to share between two slots, given that AMD allows multi-GPU (including SLI) with the B550. Apparently, the lane switches are there for a different, more fascinating reason.
A BenchLife.info report points to the possibility of all three M.2 slots on this motherboard having PCI-Express gen 4.0 wiring - something that shouldn't normally be possible, since all downstream PCIe lanes put out by the B550 are gen 3.0. The way we see it, the topmost M.2 slot has a direct PCI-Express 4.0 x4 connection from the AM4 socket (as it normally should). The second- and third slots, however, pull their wiring from a series of lane switches that split the main x16 PEG slot to gen 4.0 x8/x4/x4. It's possible that one of the two x16 (electrical x4) slots has a further lane sharing arrangement with one of the two M.2 slots.
When paired with a "Matisse" or "Vermeer" processor, the main PEG slot will run at full x16 bandwidth until one of the bottom two M.2 slots is populated, at which point the x8/x4/x4 configuration is engaged. When paired with a "Renoir" APU, however, it's likely that the bottom two M.2 slots are completely disabled, since the APU only spares 8 lanes toward PEG, which make up the first 8 (permanent) lanes on the PEG slot. The B550 chipset's 8-lane PCIe gen 3.0 budget is spent driving the board's various onboard controllers (except HD Audio, which is wired to the CPU), and one of the x16 (electrical x4) slots. GIGABYTE is expected to launch the B550 AORUS Master sometime mid-June, 2020.
Source:
BenchLife.info
A BenchLife.info report points to the possibility of all three M.2 slots on this motherboard having PCI-Express gen 4.0 wiring - something that shouldn't normally be possible, since all downstream PCIe lanes put out by the B550 are gen 3.0. The way we see it, the topmost M.2 slot has a direct PCI-Express 4.0 x4 connection from the AM4 socket (as it normally should). The second- and third slots, however, pull their wiring from a series of lane switches that split the main x16 PEG slot to gen 4.0 x8/x4/x4. It's possible that one of the two x16 (electrical x4) slots has a further lane sharing arrangement with one of the two M.2 slots.
39 Comments on GIGABYTE B550 AORUS Master Waltzes Around Chipset Limitations to Provide Three Gen 4 M.2 Slots
The final PCIe 3.0 x1 lane is obviously going for the Wi-Fi card, not USB 3.x.
www.techpowerup.com/forums/posts/4259445The point is, if you can live with eight PCIe lanes for your graphics card, you get more bandwidth for other peripherals.
The additional cost for this type of layout is most like not more than $5-10 in parts, depending on the current cost of PCIe 4.0 switches.
Not every X570 board is going to do everything better than every B550 board, get that out of the system.
B550 is 99$ and upwards, and if AIBs want to make 250$ ones, they will, and include components to their hearts and technical limitations content.
Damn I'm behind.
2 NVMe drives and 1 GFX and you already have a slowdown on potential performance on a 550.
There are x570's that cost less than $150 that already have more useable potential than any 550...
But none of that is going to affect the average user whatsoever and will get to enjoy every benefit of PCI-E 4.0
The thing about beefy VRMs is unless you're buying the upper end "good enough" is good enough.
AMD has such a good binning system that OC'ing for most is 100 maybe 200mhz.
If you want a faster AMD...buy it and spend less on the mobo.
If 550's are more than $99 they're not worth it for any reason
EDIT:
The splitting of PCI-E lanes matter..1x 16 and 1x 4 with a chipset 3.0x 4 speed limitation
They do: x16,0,0 - x8,x8,0 - x8,x4,x4
The trade off is that you get to use the m.2 x4 lanes without giving up the 1x slots *cough* MSI *cough* or your sata ports.
Honestly PCIe 3.0 is fast enough for most NVME drives. The only 4.0 drives that keep sustained speeds high enough cost Linus money and are add in card format.
Though if you add in a third slot device no SLI for you!
x8,x8, sure, but nothing more, as there's no reason for it. The last x4 slot should always be connected to the chipset and I haven't seen any board that doesn't do this, that has a third x16 slot. In fact, I'm using the x4 slot on my board with a 10Gbps Ethernet card and it's not shared with anything else in my system.
As per below, there's no reason to do something like that.
I guess they picked 8 SATA ports over having a sensible PCIe layout.
download.asrock.com/Manual/X570%20Taichi.pdf#page=36&zoom=100,0,0
They don't do anything funny it seems as they disable last pci-e 4.0 from chipset with 3rd m2 installed.
Bios option is available to any asrock x570 board for (4x4x4x4) that is Bifurcation of your 16x slot\lanes for either 8x\8x or 4x4x4x4x
This is going to be an insane mess for people to understand when they get a B550 board and wants to put things in all the slots, as people just expects it to work if there's a spare slot.
That's not exactly a problem at the moment. Probably won't be for most.