Will my RX6500XT be using PCI-E 4.0?

[cptwhite_uk]

I had assumed the set-up I'm currently building would support PCI-E 4.0 for the RX 6500 XT, now I have some doubt, can someone weigh in on this and confirm:

Ryzen 3100 - 3000 series supports PCI-E 4.0
ASrock B550M Steel Legend - supports PCIE 4.0
RX 6500 XT 4Gb Sapphire Pulse

B550 I believe still uses 4.0 to the on the top PCI-E slot, so I should get the bandwidth benefit to the RX6500XT, but all other slots will run at PCI-E 3.0 speeds? Am I correct in assuming that?

[AGTDenton]

From what I can see in the manual the board should be running at PCIe 4.0 on the PCIE1 slot with your CPU.
The other slots are PCIe 3.0 regardless of CPU.

From the pictures, the top slot is PCIE1 so you've installed it correctly, so you should be in PCIe 4.0 mode.

I've also found the 6500 XT is PCIe 4.0 - not mentioned clearly on AMD but many review & spec sites say PCIe 4.0 - Techpowerup mentions it as only a 4x card though. Perhaps this is where you may be thinking it's not at PCIe 4.0

[Jonj1611]

From the manual

PCIe slots:
PCIE1 (PCIe 4.0 x16 slot) is used for PCI Express x16 lane width graphics cards.
PCIE2 (PCIe 3.0 x1 slot) is used for PCI Express x1 lane width cards.
PCIE3 (PCIe 3.0 x16 slot) is used for PCI Express x4 lane width graphics cards.

[cptwhite_uk]

Thanks, that's what I thought, but I just wanted somene else to confirm it!

[Jonj1611]

As AGTDention said it is apparently a X4 interface for PCIe 4 which is half the bandwidth of PCIe3 x 16

[DanceswithUnix]

As above it is apparently a X4 interface for PCIe 4 which is half the bandwidth of PCIe3 x 16

Eh? From the product specifications on the web page:

AMD Ryzen series CPUs (Vermeer and Matisse)
- 2 x PCI Express x16 Slots (PCIE1: Gen4x16 mode; PCIE3: Gen3 x4 mode)*
AMD Ryzen series APUs (Cezanne and Renoir)
- 2 x PCI Express x16 Slots (PCIE1: Gen3x16 mode; PCIE3: Gen3 x4 mode)*
AMD Ryzen series APUs (Picasso)
- 2 x PCI Express x16 Slots (PCIE1: Gen3x8 mode; PCIE3: Gen3 x4 mode)*

 1 x PCI Express 3.0 x1 Slot
- Supports AMD Quad CrossFireX™ and CrossFireX™
- 15μ Gold Contact in VGA PCIe Slot (PCIE1)
- 1 x M.2 Socket (Key E), supports type 2230 WiFi/BT PCIe WiFi module

and this is a Matisse cpu, so PCIe1 is x16 Gen 4 (which is exactly what I would expect on a B550).

So slot 3 is x4, and also PCIe gen 3 (but then that's good enough for both the PCIe IO cards I have in this box).

It's all good.

[Jonj1611]

I was talking about the graphics card

Interface
PCI-Express 4.0 x4

https://www.sapphiretech.com/en/cons...00-xt-4g-gddr6

Updated my post to clarify what I was talking about

[DanceswithUnix]

I was talking about the graphics card

Interface
PCI-Express 4.0 x4

https://www.sapphiretech.com/en/cons...00-xt-4g-gddr6

Ah, the perils of using "it" in a sentence. Fair do's

[Jonj1611]

Indeed indeed Was lazy in my typing

[cptwhite_uk]

I think that's why it benefits from a PCI-E 4.0 slot - as PCI-E 3.0 x4 is limiting the bandwidth too much.

Hard to find a suitable system for a RX6500XT, given it needs a B550 board to maximise it's potential. But I picked up a Ryzen 3100 for £40, and the B550M Steel Legend for £60, and the RX6500XT for £90, so it seemed just about acceptable.

[Jonj1611]

Certainly a strange configuration, wonder why they chose x4 rather than x16. Cost?

[DanceswithUnix]

Certainly a strange configuration, wonder why they chose x4 rather than x16. Cost?

Partly.

Supposedly the chip was intended for laptops, and even x8 would have used more power driving those high energy serial lines which means worse battery life and better (more expensive) cooling. The laptop designer could make sure it was fed with PCIe4 lanes so that wasn't a customer facing concern.

Then you couldn't buy desktop GPUs, so AMD stuck them on desktop boards.

[Xlucine]

Partly.

Supposedly the chip was intended for laptops, and even x8 would have used more power driving those high energy serial lines which means worse battery life and better (more expensive) cooling. The laptop designer could make sure it was fed with PCIe4 lanes so that wasn't a customer facing concern.

Then you couldn't buy desktop GPUs, so AMD stuck them on desktop boards.

Laptops also mean lower clocks, so the same silicon performs worse - that'll take the pressure off the PCIe bandwidth.

Laptop OEMs could have chosen to leave the extra lanes unconnected (if the GPU is a cromulent PCIe device it should automatically realise it only has 4 lanes to use), and that should save power, but then that's more silicon that AMD has to pay for.

[DanceswithUnix]

Laptops also mean lower clocks, so the same silicon performs worse - that'll take the pressure off the PCIe bandwidth.

Laptop OEMs could have chosen to leave the extra lanes unconnected (if the GPU is a cromulent PCIe device it should automatically realise it only has 4 lanes to use), and that should save power, but then that's more silicon that AMD has to pay for.

In previous gen a PCIe x8 connected GPU wouldn't really have raised an eyebrow. In a world where you know for certain it is going to be connected to PCIe 4 then getting the same throughput with only 4 lines kind of makes sense.

Switching to gen 5 PCIe we might see more x4 cards.