Question Is PCI-E 5.0 backward Compatable

[Knight-Eagle]

Have a ASUS 790 MotherBoard PCI-E5.0 problems
Bought an ASUS 790ZX motherboard. And the video card was the RX580 8G GDDR5 (3.0) installed in the first PCI-E slot (5.0) next to the CPU. First off wouldn't boot up. took it in to the shop where the tech figured the board might be bad. He placed his card in the top slot next to the cpu slot still wouldn't work, tryed the bottom PCI-E slot and it worked fine. As for dropping my RX580 (3.0) card into the bottom slot there no room because of the power supply and case wiring. Sent the board in after getting another vidio (3.0) card placed it in the bottom slot started up worked fine Forgot to try it in the upper slot below the CPU. Now I was in contact with Asus and they told me that PCI-e (5.0) was not Compable with RX 580 (3.0) pci-e What can I do? or is there a fix besides pay over 2k for a 5.0 card

Ok been out of building computers and forums for a spell long spell;
most of the parts are less than 3 months old

As for version of bios currient for Asus which they are upgrading since they have the board now. Will be getting the board back in three weeks.

 

[Lutfij]

Welcome to the forums, newcomer!

To answer your thread title's question, Yes.

When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.

 

[CountMike]

They are backward and forward compatible but particular BIOS nay not be able to detect it with such spread of versions. Unfortunately your CPU doesn't have IGPU so you can't plug monitor into MB. Somewhere in BIOS there should be a setting for primary PCIe to work in v4.0 or even 3.0 mode. You need some way to access BIOS to do it.

 

[chillhouse1]

yes, it has a backward compatibility with 4 and pci express 3 as well

 

[dwd999]

I'm concerned about your Windows 10 comment. Are you saying that if you detached all of your drives the system would not even boot to bios with your gpu in any slot? Are you saying that with all of your drives detached you cannot boot to a usb stick containing the Windows 11 installer or a Linux distro with your gpu in any slot? Are you sure this is a hardware problem and not a Windows problem? (And this is why I would never recommend that anyone buy an F cpu since you really need a igpu to help diagnose this).

 

[Knight-Eagle]

My fingers sometimes type fast than my thoughts lol. After I had the Computer put together around the Asus Motherboard. With the RX580 vidio card installed in the first PCI-E slot (Ver5). It wouln't Boot or it seemed that it didnt Boot. Had the HHD at the time of build was running Win10. Before taking it to the shop. I slowly remove item's to see what was causing it not to Boot. Before I knew that I had to have a vidio card to have vidio because I had a F-type I7.14700f CPU. I even removed the vidio card. After getting the report from the shop and the computer I used another vidio card from AMD (ver3) pci-e in the lower PCI_E (ver3) first try at Booting it up from the shop without the RX580 card. It failed, again removed items one by one. nothing. I thought nothing too lose I tryrd a boot USB then i got it up to the boot screen.
When I get the Asus board Home I'll place the m2 SSD card and the new SATA 12T HHD also the 128MB ram lastly again the RX580 card will be loading win10 fresh install

 

[Knight-Eagle]

I'm concerned about your Windows 10 comment. Are you saying that if you detached all of your drives the system would not even boot to bios with your gpu in any slot? Are you saying that with all of your drives detached you cannot boot to a usb stick containing the Windows 11 installer or a Linux distro with your gpu in any slot? Are you sure this is a hardware problem and not a Windows problem? (And this is why I would never recommend that anyone buy an F cpu since you really need a igpu to help diagnose this).

If I had knowing that F on the CPU would mean that I could not boot without a vidio card i would not of bought it. At Amazon, Ebay, other sites they list the CPU like I7 14000F or I7 14000 yet not tell you if it would run vidio or needed a card and what the F ment. This not my first working at building a computer. If I was going to tell someone which one to buy would be not to get the F chip.

 

[Knight-Eagle]

Well back to where I started here. I sent the motherboard off to Asus and they checked it out everything worked and checked out. It arrived back today and installed it made sure everything was hooked up. Then started the computer up. Nothing happend not a thing, black screen only. So I powered down and removed my rx580 card and installed my smaller card first in the 1st PCI-E still didnt work. Tryed the second slot PCI-E and it then would boot up. Both cards are ver3.0 PCI-E but rx-580 card wouldnt fit in that slot. So why cant I use the first slot.

 

[thestryker]

What is the motherboard model? (what you have listed doesn't match any model)

PCIe is completely backwards compatible so that isn't a problem. Sometimes there can be problems with BIOS incompatibilities, but if the card works in the lower slot but not in the upper slot then this isn't the issue.

Assuming Asus properly tested the motherboard then there could be a problem with your CPU. The only way to verify that would be by trying a difference CPU in the motherboard.

 

[Knight-Eagle]

What is the motherboard model? (what you have listed doesn't match any model)

PCIe is completely backwards compatible so that isn't a problem. Sometimes there can be problems with BIOS incompatibilities, but if the card works in the lower slot but not in the upper slot then this isn't the issue.

Assuming Asus properly tested the motherboard then there could be a problem with your CPU. The only way to verify that would be by trying a difference CPU in the motherboard.

I heard somewhere or even read it here, cant remmeber for sure, but it stated yes backward yet that was 3.0 to 2.0 not 1.0 I did mention the name Asus 790ZX can be found at most all stores and web sites. Think I didnt mention (TUF Gaming) So I just dont see where you got your score at. Well I now have three votes saying you are just sending ??? out there sounding like you know something. Maybe you do you just havent been here. I have one computer shop one maker and what i've seen myself. the smaller vidio card I bought fits in both slots is a GT 730 graphics card both are from the same maker. When I sent this MB in to ASUS I sent in a detail list of all parts and what was done and by who. They couldnt cause it to happen again. I will look ino the bios yet i have my doughts at Asus they updated the bios then tested again same resuts evrything fine. As for trying a defferent CPU feel free to mail be one.

 

[Knight-Eagle]

Entered the bios searched for the PCI-E the results showed if i remmber right pci-e on startup <disable> other choice in the drop down was (enable) the setting was set to <disable>

 

[DRagor]

The problem is not in PCie as it is both backwards and forward compatible. More likely is comes from new boards having Secure Boot enabled by default and it will not play nice with old GPU. Since you can use different GPU to boot to BIOS you can try something like this: boot to BIOS with other GPU, disable TPM and Secure Boot, save and restart to BIOS, make sure the changes have been made, power down the rig and swap GPU for 580. Once you install Windows let it install video drivers for your 580 and at this point you should be able to enable Secure boot again if you need it.

 

[Dashhh]

Good morning, Knight-Eagle!

First, to answer your question... Yes. PCIe generations are backwards/forwards compatible. There is a catch, however. Just because your board supports newer PCIe speeds, that doesn't mean you'll get them pending where you slot your hardware. Your CPU supports Gen5 PCIe, so if you follow your slots properly when installing your NVMe SSD's, HDD's, etc, you'll be able to support Gen5 speeds. Take a look at your motherboards manual to see which slots support which speeds. Due to lane architecture, some boards in these generations will have like 3 ssd slots but only allow you you use M.2_2 and M.2_3 if you want to use your PCIe 5.0 slot (x16 slot) for your graphics card or whatever.

I was also reading some basic specs on your Asus board and the manual shows that the only slot on that board that supports Gen5 PCIe is the PCIe_1 (x16) which is great, but again your card supports at max Gen3 speeds, so regardless you'll be throttled and your board might not even recognize it. Since your CPU powers Gen5 lane architecture, this is sounding more like a BIOS misconfiguration to me. Head into your bios and there should be an option in there to change from Gen3 or 4 to Gen5. After that, your card will most likely be recognized in that PCIe slot, but it would only run at PCIe3 speeds.

 

[thestryker]

You can try manually setting PCIe in the BIOS under Advanced > PCI Express Configuration

There is also a Graphics Configuration section under the Advanced tab where you could make sure it is set to use PCIe.

You can also reset the BIOS to defaults though I imagine this has already been done and likely multiple times.

It's possible these settings may have an impact, but if the CPU is the issue then they will do nothing.

I did mention the name Asus 790ZX can be found at most all stores and web sites. Think I didnt mention (TUF Gaming)

There's no such thing as a 790ZX period so while I assumed you were talking about an Asus Z790 motherboard they sell dozens of different Z790 models. The TUF Gaming is the important part as that allows everyone to know which Asus Z790 motherboard you're talking about.

When I sent this MB in to ASUS I sent in a detail list of all parts and what was done and by who. They couldnt cause it to happen again. I will look ino the bios yet i have my doughts at Asus they updated the bios then tested again same resuts evrything fine.

Asus will have just tested with whatever standard components they use to make sure everything is working.

As for trying a defferent CPU feel free to mail be one.

If it's not the motherboard and it's not the video card that is the only thing left. You said the shop tried their own card in the top slot and it didn't work, but the bottom did. You also currently have a card that doesn't work in the top slot but does in the bottom. Asus said the motherboard works which means the only thing left would be the CPU as that provides the PCIe lanes to that top slot.

 

[Knight-Eagle]

Good morning, Knight-Eagle!

First, to answer your question... Yes. PCIe generations are backwards/forwards compatible. There is a catch, however. Just because your board supports newer PCIe speeds, that doesn't mean you'll get them pending where you slot your hardware. Your CPU supports Gen5 PCIe, so if you follow your slots properly when installing your NVMe SSD's, HDD's, etc, you'll be able to support Gen5 speeds. Take a look at your motherboards manual to see which slots support which speeds. Due to lane architecture, some boards in these generations will have like 3 ssd slots but only allow you you use M.2_2 and M.2_3 if you want to use your PCIe 5.0 slot (x16 slot) for your graphics card or whatever.

I was also reading some basic specs on your Asus board and the manual shows that the only slot on that board that supports Gen5 PCIe is the PCIe_1 (x16) which is great, but again your card supports at max Gen3 speeds, so regardless you'll be throttled and your board might not even recognize it. Since your CPU powers Gen5 lane architecture, this is sounding more like a BIOS misconfiguration to me. Head into your bios and there should be an option in there to change from Gen3 or 4 to Gen5. After that, your card will most likely be recognized in that PCIe slot, but it would only run at PCIe3 speeds.

 

[Knight-Eagle]

Well I've I desided just to live with using the lower PCI-E slot the computer is up and running. Only thing that has me pissed is having to buy the 2nd vidio card and folks not telling about the letter F on the CPU's back when i was looking for the processor. WHat made me decide just be happy for what is where im at was when I looked into the Bios for the PCI-E listed 6 items i could change from gen 1 up to gen 4. thought i would keep the build where it is and not try to mess with the bios that where i draw the line at just dont feel conferable making the changes there.