Solved Is my GPU running on PCIe 4.0 or 3.0 ASUS ROG Strix B550-F Gaming AMD AM4 Zen 3 Ryzen 5000 & 3rd Gen Ryzen ATX Motherboard (PCIe 4.0

CountMike said:

All modern consumer grade CPUs controll 24 PCIe lanes, server grade like Xeon, Threadripper, Epyc double or more.
Of those 24, 4 are dedicated to communication with Chipest and 16 to communication with 1 or 2 PCIe x16 slots/busses. First x16 slot has 16 of those lines but if 2 of those first two x16 slots are used PCIe lanes are divided between them in 8+8 lines.
That leaves other 4 PCIe lanes to be used by eventual PCIe x1/x4 or M.2 NVMe slots/busses.
PCIe x16 slot doesn't "share" PCIe lanes with M.2 NVMe slots, inserting NVMe SSD in M.2 slot is not going to "steal" any PCIe lanes from CPU or can gain any if none of x16 slots is not used, it simply has 4 lames allocated to it and if no NVMe SSD is used they are just "wasted".
Generation of those 16 lanes is determined by CPU and BIOS options.
Wiring/traces are same for all PCIe generations, it's only frequency/bandwidth that changes so they are all up and down compatible. Every PCIe generation doubles the bandwidth/speed of previous generation but uses it's bandwidth/speed of earlier one.

It's similar with Chipset controlled/provided PCIe lanes but that doesn't depend on CPU PCIe generation. It also generates and distributes them same way and can have different generation from CPU. Cheaper MB Chipsets usually have less and/or earlier generation lanes that those of top grade. Chipsets also control most of I/O operations like for instance SATA so if they have less PCIe lanes, they may share them with SATA ports so some of them may become unavailable if M.2 or PCIe U (usually x4 or x1) are used.

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bobkn said:

There are some additional complications.

I have an Asus Z690-E motherboard. Its M.2_1 slot is PCI-E 5.0.

If that slot is populated with any PCI-E version M.2 drive, the graphics slot drops back from X16 to X8. That's with an I9-13900K, which has 16 PCI-E 5.0 lanes plus 4 PCI-E 4.0 lanes. There are some Z690 boards that use the 4 PCI-E 4.0 lanes for M.2_1, so the graphics slot gets 16 lanes even if an M.2 drive is used in the CPU driven slot.

(I don't know about any additional dedicated lanes for communication with the motherboard.)

The same applies to the I9-14900k (16 lanes at 5.0, 4 at 4.0).

The AMD 5700G is spec'd with 16 PCI-E 3.0 lanes. AMD Ryzen 7 5700G Specs (That may have something to do with it being an "APU", with relatively high integrated graphics performance.)

A 5700X, 20 PCI-E 4.0 lanes. AMD Ryzen 7 5700X Specs

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CountMike said:

Yeah, if there are more than one M.2 slot connected to CPU that has NVMe installed it has to share those 24 PCIe lanes as with all other. NVMe runs on 4 lanes for full speed but can run on less with some speed loss.
Ryzen G series (APU) still have 24 lanes but 4 are dedicated to IGPU so only 20 available for other stuff. They also have earlier gen PCIe because IGPU can run only at gen 3. Even if disabled it still stays at gen3, early ones gen2. Ryzen has I/O (including IGPU) chip separate from chip eith cores. AM5 ( Zen4, 7000 and 9000 series) has IGPU that doesn't use PCIe lanes but it's not considered an APU. New, real APUs with powerful graphics are coming soon, Present ones are a bit better than Intel but still very basic. Don't know if and how many dediicated PCIe lanes they'll have. Ryzen 8000G series, same as 5000 have only gen3 and use 4 PCIe lanes.

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BamaInArk said:

It must be remembered that the motherboard design has a lot to due with PCIe lane support or lack thereof more so than the CPU itself. More expensive motherboards typically support more PCIe hardware. Cheaper motherboards simply offer less connectivity. Then you've got CPU connections vs Chipset connections.

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bobkn said:

The 20 lanes for the 5800XT were for the CPU only.

What CPU are you using? An old Xeon?

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CountMike said:

All modern consumer grade CPUs controll 24 PCIe lanes, server grade like Xeon, Threadripper, Epyc double or more.
Of those 24, 4 are dedicated to communication with Chipest and 16 to communication with 1 or 2 PCIe x16 slots/busses. First x16 slot has 16 of those lines but if 2 of those first two x16 slots are used PCIe lanes are divided between them in 8+8 lines.
That leaves other 4 PCIe lanes to be used by eventual PCIe x1/x4 or M.2 NVMe slots/busses.
PCIe x16 slot doesn't "share" PCIe lanes with M.2 NVMe slots, inserting NVMe SSD in M.2 slot is not going to "steal" any PCIe lanes from CPU or can gain any if none of x16 slots is not used, it simply has 4 lames allocated to it and if no NVMe SSD is used they are just "wasted".
Generation of those 16 lanes is determined by CPU and BIOS options.
Wiring/traces are same for all PCIe generations, it's only frequency/bandwidth that changes so they are all up and down compatible. Every PCIe generation doubles the bandwidth/speed of previous generation but uses it's bandwidth/speed of earlier one.

It's similar with Chipset controlled/provided PCIe lanes but that doesn't depend on CPU PCIe generation. It also generates and distributes them same way and can have different generation from CPU. Cheaper MB Chipsets usually have less and/or earlier generation lanes that those of top grade. Chipsets also control most of I/O operations like for instance SATA so if they have less PCIe lanes, they may share them with SATA ports so some of them may become unavailable if M.2 or PCIe U (usually x4 or x1) are used.

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Scannerman said:

It's an old Intel i9 series chip that used to get rave reviews back in the day when Thread Ripper was a thing. I got it cheap with the board so I decided to try it.

i9 7960X

It doesn't overclock as easily as the 6900K (which, to make matters even more confusing, is categorized by Intel as an X series chip as well) and for whatever reason I can't get Thunderbolt 3 to work with it so that card will have to go back in my non-compliant with Win11 X99 board.


I suppose the i9 7960X could be classified as a "server grade" chip but methinks it is more of a work station chip for back when work stations were in fact WORK stations. Alas, the only PCIe slot that ASUS has designated for Thunderbolt on the SAGE work station board is PCIe x16_2; which, is conveniently tucked underneath the GFX card. Moving the graphics card is possible but in either case I cannot get Thunderbolt to work with this board. Intel diagnostics and HWNiNFO show board is healthy so . . I dunno. Guess I'll be keeping the X99 for a while.

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bobkn said:

A Socket 2066 chip. I'd call it an HEDT (high end desktop) CPU. From 2017. Intel® Core™ i9-7960X X-series Processor (22M Cache, up to 4.20 GHz) - Product Specifications | Intel

From the only Gen7 family that's approved for Windows 11.

Intel seems to have abandoned that market after Gen10. I guess we could use server hardware in lieu of that.

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ASUS X299 SAGE

The system board came in today. I'll be giving it a thorough inspection before putting it on the test bench. I purchased it second hand as there are likely not many brand new boards like this available and the ones that are would likely cost a fortune. One more system board spared from a...

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