ASRock.com Homepage
Forum Home Forum Home > Technical Support > AMD Motherboards
  New Posts New Posts RSS Feed - Video card bandwidth in PCIE3 slot of X570 Taichi?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Video card bandwidth in PCIE3 slot of X570 Taichi?

 Post Reply Post Reply Page  123>
Author
Message
shmerl View Drop Down
Newbie
Newbie


Joined: 23 Oct 2017
Status: Offline
Points: 197
Post Options Post Options   Thanks (0) Thanks(0)   Quote shmerl Quote  Post ReplyReply Direct Link To This Post Topic: Video card bandwidth in PCIE3 slot of X570 Taichi?
    Posted: 14 Aug 2019 at 7:02am
X570 Taichi manual says:


Quote Matisse: 3 x PCI Express 4.0 x16 slots (PCIE1/PCIE3/PCIE5: single at x16 (PCIE1); dual at x8 (PCIE1) / x8 (PCIE3); triple at x8 (PCIE1)/ x8 (PCIE3) / x4 (PCIE5)


Does it mean that single video card will operate in PCIe x16 mode only in PCIE1 slot? What will happen if I put it in PCIE3 slot? It would a better fit in my case. It won't operate at x16?

My CPU is Ryzen 9 3900X.
Back to Top
Ray62 View Drop Down
Groupie
Groupie
Avatar

Joined: 01 Jul 2018
Location: Germany, Berlin
Status: Offline
Points: 552
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ray62 Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 2019 at 2:06pm
Yes, only the PCIE1 has wired 16 lanes as in every AM4 board. See manual:
PCIe slots:
PCIE1 (PCIe 4.0 x16 slot) is used for PCI Express x16 lane width graphics cards.
PCIE2 (PCIe 4.0 x1 slot) is used for PCI Express x1 lane width cards.
PCIE3 (PCIe 4.0 x16 slot) is used for PCI Express x8 lane width graphics cards.
PCIE4 (PCIe 4.0 x1 slot) is used for PCI Express x1 lane width cards.
PCIE5 (PCIe 4.0 x16 slot) is used for PCI Express x4 lane width graphics cards
Asrock Fatal1ty X370 Professional Gaming Offline
Under test:
MSI X570_MEG_ACE | AMD Ryzen 9 3900X | Scythe Mugen5 | 2x16GB F4-3200C14D-32GTZ@3466 | ASUS GeForce GTX 1080 Ti FE
Back to Top
shmerl View Drop Down
Newbie
Newbie


Joined: 23 Oct 2017
Status: Offline
Points: 197
Post Options Post Options   Thanks (0) Thanks(0)   Quote shmerl Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 2019 at 2:09pm
Why are then PCIE3 and PCIE5 slots referenced as (PCIe 4.0 x16 slot) if they can't ever operate in x16 mode? That's a bit confusing.
Back to Top
Ray62 View Drop Down
Groupie
Groupie
Avatar

Joined: 01 Jul 2018
Location: Germany, Berlin
Status: Offline
Points: 552
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ray62 Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 2019 at 3:35pm
They must be mechanically compatible for GPUs, even if they only use 8 or 4 lanes. But that is a very old thing for mainstream motherboards.

If you want more fully PCI Express x16 lanes slots, you have to use a Threadripper or Intel socket 2066 board.
Asrock Fatal1ty X370 Professional Gaming Offline
Under test:
MSI X570_MEG_ACE | AMD Ryzen 9 3900X | Scythe Mugen5 | 2x16GB F4-3200C14D-32GTZ@3466 | ASUS GeForce GTX 1080 Ti FE
Back to Top
gizmic View Drop Down
Groupie
Groupie
Avatar

Joined: 13 Jun 2018
Location: Hong Kong
Status: Offline
Points: 446
Post Options Post Options   Thanks (0) Thanks(0)   Quote gizmic Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 2019 at 3:53pm
thats like saying why usb 1 doesnt do usb 3.0
Back to Top
ksquared View Drop Down
Newbie
Newbie


Joined: 11 Aug 2019
Location: Florida
Status: Offline
Points: 13
Post Options Post Options   Thanks (0) Thanks(0)   Quote ksquared Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 2019 at 9:50pm
Originally posted by shmerl shmerl wrote:

Why are then PCIE3 and PCIE5 slots referenced as (PCIe 4.0 x16 slot) if they can't ever operate in x16 mode? That's a bit confusing.


Yes, I'd agree about being confusing. They are physical x16 slots, but won't operate as x16 slots.

To me, even more confusing is that once you use both PCIE1 and PCIE3, the PCIE1 slot then drops from the x16 and becomes an x8 mode. But I guess most (or all) video cards can still operate fine in the x8 mode?

So then, is it if you use PCIE1 and the PCIE5 slot, the PCIE1 slot will still drop from the x16 and become an x8 mode? That is the way I'd read the manual, but if you add up the potential 8+8+4 you have 20 lanes, so is it possible the PCIE1 slot would remain x16 and the PCIE5 slot as x4?

Back to Top
Ray62 View Drop Down
Groupie
Groupie
Avatar

Joined: 01 Jul 2018
Location: Germany, Berlin
Status: Offline
Points: 552
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ray62 Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 5:31am
Originally posted by ksquared ksquared wrote:


So then, is it if you use PCIE1 and the PCIE5 slot, the PCIE1 slot will still drop from the x16 and become an x8 mode? That is the way I'd read the manual, but if you add up the potential 8+8+4 you have 20 lanes, so is it possible the PCIE1 slot would remain x16 and the PCIE5 slot as x4?


PCIE1 and PCIE3 are connected to the CPU and use 16 lanes, either in 16-0 or 8-8 mode. The answer to your first question is no.
PCIE5 and M2_3 are connected with 4 shared lanes to the chipset, so only one can be used at the same time.
So, if M2_3 is not in use, the answer to your second question is yes.
Asrock Fatal1ty X370 Professional Gaming Offline
Under test:
MSI X570_MEG_ACE | AMD Ryzen 9 3900X | Scythe Mugen5 | 2x16GB F4-3200C14D-32GTZ@3466 | ASUS GeForce GTX 1080 Ti FE
Back to Top
shmerl View Drop Down
Newbie
Newbie


Joined: 23 Oct 2017
Status: Offline
Points: 197
Post Options Post Options   Thanks (0) Thanks(0)   Quote shmerl Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 9:38am
Originally posted by Ray62 Ray62 wrote:

PCIE1 and PCIE3 are connected to the CPU and use 16 lanes, either in 16-0 or 8-8 mode.


If both are connected to the CPU, what exactly prevents PCIE3 from operating in x16 with only one device in it? It shouldn't be hard to detect that only one device is in use, and not to split the bandwidth.
Back to Top
Ray62 View Drop Down
Groupie
Groupie
Avatar

Joined: 01 Jul 2018
Location: Germany, Berlin
Status: Offline
Points: 552
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ray62 Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 3:56pm
I agree, 0-16 mode sounds possible, but not mentioned in the manual.
ASUS X570 Strix Series for example offers the same.
16-0, 8-8, 0-8 mode is given for X370/X470/X570 boards since the beginning of the Ryzen platform. I don't know if there are any exceptions.

Ask Asrock support, if the PCIE3 slot has 16 or only 8 lanes wired.
Asrock Fatal1ty X370 Professional Gaming Offline
Under test:
MSI X570_MEG_ACE | AMD Ryzen 9 3900X | Scythe Mugen5 | 2x16GB F4-3200C14D-32GTZ@3466 | ASUS GeForce GTX 1080 Ti FE
Back to Top
gizmic View Drop Down
Groupie
Groupie
Avatar

Joined: 13 Jun 2018
Location: Hong Kong
Status: Offline
Points: 446
Post Options Post Options   Thanks (0) Thanks(0)   Quote gizmic Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2019 at 5:37pm
flip the board around you'll see the pins are different on pcie1 and pcie3. if it only reaches half way its only wired for x8
Back to Top
 Post Reply Post Reply Page  123>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 11.06
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.078 seconds.