[SOLVED] Doubts with the bandwidth of pci express.

Sep 6, 2019
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Hello, I have searched the Internet for a long time without fully understanding the bandwidth of the motherboard's express pci, with those of a video card. I see that they are measured differently and I don't know what the limit is.

I have an All in One.

I7- 4790s
16gb ram
500ssd

I have a rx 270 video card

With a 16x to 1x adapter

I see that my 1x express pci is 2.0, I don't know where to see it with certainty.

My doubt, until what video card can I place without being limited by the pci express x1.

I want to buy a rx 590.

Already for next year, if I change the entire pc, because even to work I am left over in spec.

If someone can explain to me well, how to know how much bandwidth a video card needs, to know the limit with the express pci I would appreciate it.

Regards!
 
There are fewer PCIe scaling tests for AMD GPUs, but this should still help:

The FuryX is only slightly more powerful than the RX590. As you can see, there is a 20% drop in performance going to the equivalent of PCIe 2.0 x2, so it would be reasonable to expect a further halving of the bandwidth would lead to only ~60% of the expected performance.

The 7970 here is only slightly more powerful than your R9 270 as it is essentially a 280X. Like the FuryX, it appears to also lose ~4% when PCIe bandwidth is cut to 1/8, so probably is also severely hampered by cutting bandwidth to 1/32 despite being a much lower performance card to begin with. In general, only very slow cards aren't hobbled when cutting the bandwidth that severely.

Note that any x1 slots are also connected to your CPU over DMI 2.0, which means they must share the bandwidth of all hard drives and USB devices over the equivalent of a PCIe 2.0 x4 link.
 
PCI-E is backwards compatible, meaning even if your Motherboard supports gen 2.0, any gen 3.0 GPU will also work on that same board.

There won't be any performance drop whatsoever (you won't even notice it while gaming).

All PCI Express versions are backward and forward compatible, meaning no matter what version the PCIe card or your motherboard supports, they should work together, at least at a minimum level. One important thing to know, however, is that to get the increased bandwidth (which usually equates to the greatest performance), you'll want to choose the highest PCIe version that your motherboard supports and choose the largest PCIe size that will fit.

For example, a PCIe 3.0 x16 video card will give you the greatest performance, but only if your motherboard also supports PCIe 3.0 and has a free PCIe x16 slot. If your motherboard only supports PCIe 2.0, the card will only work up to that supported speed (e.g., 64 Gbit/s in the x16 slot).

The only slight disadvantage is that it will only have the maximum bandwidth provided by the slot; i.e., if you install an x16 video card in an x4 slot, it will have only x4 bandwidth available.

To reach the maximum performance possible, both the expansion card and the PCI Express controller (available inside the CPU or inside the motherboard chipset, depending on your system) have to be of the same revision. If you have a PCI Express 2.0 video card and install it on a system with a PCI Express 3.0 controller, you will be limited to the PCI Express 2.0 bandwidth. The same video card installed on an old system with a PCI Express 1.0 controller will be limited to the PCI Express 1.0 bandwidth.
 
Sep 6, 2019
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Hi, thank you very much for answering, the part you expose is the one I understand :)

The part I don't understand is that a 2.0 express pci works at 500mb / s

But graphics cards say 200gb / s

I don't understand conversions very well.

My motherboard is a frankenstein
https://prnt.sc/p2s21b

I don't see spec on her internet.


This is my adapter, for the video card.

I want to know if the bandwidth of a rx 590 can work without a bottleneck, on a pci express x1 2.0 / or it needs more bandwidth.

I have seen people who test configurations with 1080ti in x1 only losing 10% performance.

but I want to be sure how much you need a 590.
 
Sep 6, 2019
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In this case the energy is not a problem, because I feed the video card with an external powersuply termalteck 600w 80 plus

My doubt is, if a pci express x1. It is enough for a rx 590.

and how to know how much of pci express bandwidth, consume a video card. so that I can see my purchase options for this year.
 
I want to know if the bandwidth of a rx 590 can work without a bottleneck, on a pci express x1 2.0 / or it needs more bandwidth.
Like I said before, installing any GPU on a lower version/revision PCI-E motherboard would be limited by the bandwidth available of that slot, be it x1 or x2. It will need more bandwidth to get the maximum performance of the card though.

The only slight disadvantage is that it will only have the maximum bandwidth provided by the slot; i.e., if you install an x16 video card in an x4 slot, it will have only x4 bandwidth available.

For example, a PCIe 3.0 x16 video card will give you the greatest performance, but only if your motherboard also supports PCIe 3.0 and has a free PCIe x16 slot. If your motherboard only supports PCIe 2.0, the card will only work up to that supported speed (e.g., 64 Gbit/s in the x16 slot).

Is this what you are asking for, or some other thing ?
 
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Sep 6, 2019
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Hi there! thanks for answering.
What you mention that I understand.

I tried to express myself more clearly:

how to know what would be the limit of a pci x1 2.0 in Gbits
what would be the top video card model that I could place.

I have tried to investigate it.

Example:

if a 590 card uses xxx / Gbits

And how much is the maximum that a 1x 2.0 express pci can use. xxx / Gbits

I have tried to understand this, but the measures I get on the Internet do not fully understand them.

I want to know the limit, which I have in terms of models according to my capacity.

if it is a 380/480 / 580. For a performance without a bottleneck.
 
bottleneck will depend on which games / which settings u will use

gpu itself shouldnt have issues, when it gets some data /textures, it will process it and send it back to cpu
bottleneck may appear if game has too large textures and too many of them, gpu will need to wait for those data (bandwith limit), some post processing (effects) shouldnt be affected as it just eyecandy stuffs which arent bandwith strained

texture fill rate will be limited, u shouldnt be using anisotrophic filtering
 
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Sep 6, 2019
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Thanks for answering :)

So there is no way to know, what would be the limit of a 1x 2.0 express pci?

I have that doubt to see until what video card I could use, in my configuration.
 
There are fewer PCIe scaling tests for AMD GPUs, but this should still help:

The FuryX is only slightly more powerful than the RX590. As you can see, there is a 20% drop in performance going to the equivalent of PCIe 2.0 x2, so it would be reasonable to expect a further halving of the bandwidth would lead to only ~60% of the expected performance.

The 7970 here is only slightly more powerful than your R9 270 as it is essentially a 280X. Like the FuryX, it appears to also lose ~4% when PCIe bandwidth is cut to 1/8, so probably is also severely hampered by cutting bandwidth to 1/32 despite being a much lower performance card to begin with. In general, only very slow cards aren't hobbled when cutting the bandwidth that severely.

Note that any x1 slots are also connected to your CPU over DMI 2.0, which means they must share the bandwidth of all hard drives and USB devices over the equivalent of a PCIe 2.0 x4 link.
 

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