[SOLVED] rtx 4090 MB x299 riser cable 3.0 computability

[HaizRail007]

Hello, I have a question About riser cables, Gpu and Motherboard. I have a x299 motherboard which runs pcie 3.0. I know that the rtx 4090 is pcie 4.0 and is backwards compatible with 3.0. Nevertheless, I am wanting to know if anyone knows if a 3.0 pcie riser cable will work connected to the rtx 4090, which will be connected to a 3.0 motherboard. I understand there will be a speed bottle neck. However the price difference between cables are massive.

so long story short will a pcie 3.0 riser cable connected to a rtx 4090 all work connected to a 3.0 motherboard.

 

[Lutfij]

However the price difference between cables are massive
Yes, rightly so, as is with the case with any new piece of tech until it's been widely adopted by the masses.

PCIe 3.0 riser cables will work with the GPU in question. I hope you've got a reliably built PSU that can deliver 1.2KW of power to the entire system. In your current state, make sure you've got the latest BIOS version for your motherboard.

 

[SkyNetRising]

will a pcie 3.0 riser cable connected to a rtx 4090 all work connected to a 3.0 motherboard.

As long as motherboard doesn't try to force PCIE 4.0 mode, you should be fine.
Though - it depends on riser cable quality and length of it.

On PCIE 4.0 compatible boards you'd have to force PCIE slot to PCIE 3.0 operation mode.

You may want to watch this:

View: https://www.youtube.com/watch?v=q5xvwPa3r7M

 

[HaizRail007]

Okay thank you very much for your response, yeah I have a seasonic vertex 1200 watt, which is replacing a 10 year old 1300 evga Super nova. and my bios is updated to the current version. I've never had to use riser cables before, but with the cards getting so big it's just unavoidable not to run a vertical mount this time. so I've ordered a custom vertical mount that will mount to my secondary psu mount so I won't have to sacrifice my expansion slots.

 

[HaizRail007]

As long as motherboard doesn't try to force PCIE 4.0 mode, you should be fine.
Though - it depends on riser cable quality and length of it.

On PCIE 4.0 compatible boards you'd have to force PCIE slot to PCIE 3.0 operation mode.

You may want to watch this:

View: https://www.youtube.com/watch?v=q5xvwPa3r7M

yeah I was wondering about cable quality and the length, because I realize the riser cables arn't made equal. but what I'll need is a 230mm - 440mm with a 90 degree angle at the gpu side. longer wouldn't hurt. and considering my motherboard doesn't support 4.0 pcie only pcie 3.0, I need a cable that won't blue screen etc. because it seems some people are have issue when buying the wrong riser cables, so and recommendations would be welcome.

 

[VegasRebel]

I registered just to say thank you. This ended days of troubleshooting and saved my sanity.

I have a B550 motherboard that supports PCIE 4.0, and just bought a rtx 4090. I used a riser cable from my previous card that was PCIE 3.0.

I was getting about 20 FPS in 3DMark Firestrike and Heaven with a 4090, which was just insane. It would do normal web tasks without an issue, but gaming performance was shot. After seeing @SkyNetRising's response above I went into BIOS and set the PCIE x16 slot to Gen 3 instead of Auto. Problem solved. (Well, mostly solved. I'm going to get a Gen 4.0 riser cable so I'm not running a 4090 in Gen 3, but FPS is basically what it should be now.)

So, thanks @SkyNetRising and OP.