2 boards, same design, different PCIE switching? (Gigabyte X299)

Hardware Hub Motherboards
1

So I’m looking at my next X299 board and I’m eyeing the Gigabyte X299 Designare EX.

Seems like the perfect board but there’s one oddity that I find extremely odd:

The 3 GPU config for the CPU PCI-E lanes is x8/x16/x8…

However, the X299 Aorus Gaming 7 Pro is the same board minus the Thunderbolt controller, but has the full x16/x16/x8…

All reviews online suggest the Thunderbolt controller on the mobo goes to the chipset, but if a fully populated board drops the first slot to x8, something weird is happening with the lane switching. If the same board design CAN support x16/x16/x8, what’s the limitation? Board design? Lane switching?

The recent Cascade Lake-X updates to the Designare allowed bifurcation of the PCI-E lane partitioning so that each x4 partition can be separated:

skl-x_pcie_lane_partitioning.png1021×783 123 KB

So then why do the lane switchers still cripple the top slot when fully populated? Were the materials not updated for Cascade Lake-X, or was the board designed that way?

I would like an lstopo on this board, and a trace analysis of it to see where the traces for that Thunderbolt controller are actually going. If the Thunderbolt controller is indeed sharing traces with the lanes for the top slot, that is honestly bad design to provide a feature, and I would literally switch over to the Aorus Gaming 7 Pro for that reason, since the lanes actually matter.

There’s no detailed block diagram for both boards so I need people who own these boards to check the traces.

If the x4 lanes from the Thunderbolt controller are going to the chipset, they should stay isolated rather than share traces. If traces are shared, it’s bad design.

I’m grasping at straws trying to figure this out… No use contacting their PR/Support since I need to actually speak to a engineer for the board to figure out why this is happening.

2

As far as i know according to Gigabyte´s page,
the Thunderbolt controller runs of the chipset.

As far as the pci-e lanes are concerned on the X299 Designare EX 10G rev1.0.

This depends on the cpu series you install it on.
Because there are 3 generations of cpu´s for x299.
48 lane cpu’s the newest gen X series, 44 lane cpu´s the previous gen X series.
And the 28 lane cpu’s.

3

Yes, I’m aware of it, but how does this particular board deal with the partitions of x4 lanes? Did that change with the Cascade Lake-X BIOS updates? since the board can perfectly do x16/x16 on both the Designare EX and the Gaming 7 Pro.

4

From what i see, the second slot shares bandwith with m.2.

5

You could basically see it from the Gigabyte´s product page.
But to be sure, it would be better to download the actual manual,
and read trought that.
Because sometimes product pages contain errors.

6

The spec shows the next physical x16 down is a x4.

This is the only block diagram I could find for the X299 Designare EX board:

lanechart

…but my confusion lies in why the top slot drops to x8 if all the direct lanes are fully populated…

7

I guess i´m looking at a different revision of the Designare x299 board?
I’m looking at the Gigabyte X299 Designare 10G rev1.0 :slight_smile:

lets dig further at Gigabytes website.

But i guess that drop might have something to do,
with previous gen lower lane count cpu´s?
Like the 28 lanes.

8

It is not the X299X 10G, it’s the X299 Designare EX.

1 Like
9

Yeah now i see i´m actually looking at the wrong board oops :blush:
Gigabyte is always very anoying with their revisions etc.

10

It’s an older board so they don’t really show,
how the lanes are shared with the 48 lane sku’s.

But like i said it has likely something to do,
with the previous gen lower lane count cpu´s.
Like the 28 lane core i7.
And there have even been 16 lane i5s and i7´s for x299 believe it or not.

But with the recent bios update for Cascade lake X 48 lane cpu´s.
I cannot really see any reason why the first slot should default back to 8x.
This should basically only happens when you use a 28 lane cpu.

That is what the image you provided is showing.
It stated above in red letters 44/28 lane cpu’s.

But of course always download and double check the actual manual of the board to be fully sure.
Before you purchase it.

11

All material says x8/x16/x8 but we don’t know for sure unless someone gets a 10900X with this board.

The only extreme overclocker I know with this board is Buildzoid, and he might not even be interested in a 10900X, but I simply want to know the partitioning of the x4 blocks on a board like this if the material is stating otherwise.

12

Could be that the third x16 slot is actually the main slot.
That is of course a possibility, that is just depending,
how Gigabyte did aply those switches.

edit: yes the third slot is the main slot.

13

And that’s the mystery… For first gen Skylake-X it makes sense, but not Cascade Lake-X.

I really hope @wendell still has the board for use with the 10980XE, to double check the lanes.

1 Like
14

True.

Looks like the third slot is indeed the main slot.

1 Like
15

Uhm, is there any reason to expect the Designare EX to support the additional features of Cascade Lake-X? There are reviews online of this motherboard as early as Oct 2017, while the Cascade Lake-X CPUs were not announced until two years later.

In Tom’s Hardware coverage of the Cascade Lake-X announcement, it says

“Intel was able to expose four additional [PCIE] lanes from the HCC die to the socket, and while these chips are compatible with existing X299 boards, you’ll likely lose those extra four lanes unless you upgrade to one of the new X-series motherboards that will also debut with the new chips.”

https://www.tomshardware.com/news/intel-cascade-lake-x-pricing-availability-launch-specifications-10th-generation,40526.html

Perhaps the changes to bifurcation could be accommodated with a BIOS update, but that might not happen (or not soon) for a board of this vintage?

P.S. Greetings to a couple of long-time forum members from a newbie.

1 Like
16

Yeah might verywell be the case.
I was confused with a different board on first hand.
Gigabyte and board revision names are…
I don’t have the said hardware to test.
But if you loose the additional four lanes,
then yeah that kinda makes sense.

I would always recommend to buy a new gen x299 board anyways.
But that is on a side note.

17

Cost wise, it’s still to prohibitive for me to get a X299X refresh board. The 2 10G ports on the X299X also can’t be IOMMU separated, since it’s 2 ports on 1 10G controller.

So the extra x4 lanes are adding onto the current x12 partition, but it still baffles me why Gigabyte engineers decided to drop the top slot to x8, when the identical board in the Aorus Gaming 7 Pro doesn’t have the issue.

18

It does with a 28 lane cpu.
With a 44 lane, you have 44 lanes available to the cpu.
So in that case from what i gather from Gigabyte’s home page,

  • Slot 3 and 1 will run a 16x.
  • Slot 5 will run at 8x.
  • Slot 2 is 4x and shares with the m.2 above,
    You can only use one of the two.
  • Slot 4 is going trough the chipset.

Unless i’m missing something?

19

The x16 partition for the top slot should be dedicated to that block of 4 x4 lanes, but the issue is it somehow isn’t according to the spec for the Designare, and it is according to the spec of the Aorus Gaming 7 Pro.

But it’s the same motherboard PCB.

1 Like
20

Okay thats kinda odd.
Then i guess the information on the spec page of the said board,
isn’t fully accurate.
Then i have to dig into the boards manual later to know for sure.