There are some additional complications.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.
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
My Computers
System One System Two
-
- OS
- Windows 11 26100.3915
- Computer type
- PC/Desktop
- Manufacturer/Model
- homebuilt
- CPU
- Amd Threadripper 7970X
- Motherboard
- Gigabyte TRX50 Aero D
- Memory
- 128GB (4 X 32) G.Skill DDR5 6400 (RDIMM)
- Graphics Card(s)
- Gigabyte RTX 4090 OC
- Sound Card
- none (USB to speakers), Realtek
- Monitor(s) Displays
- Philips 27E1N8900 OLED
- Screen Resolution
- 3840 X 2160 @ 60Hz
- Hard Drives
- Crucial T700 2TB M.2 NVME SSD
WD 4TB Blue SATA SSD
Seagate 18TB IronWolf Pro
- PSU
- BeQuiet! Straight Power 12 1500W
- Case
- Lian Li 011 Dynamic Evo XL
- Cooling
- SilverStone Technology XE360-TR5, with 3 Phanteks T30 fans
- Keyboard
- Cherry Streaming (wired)
- Mouse
- Logitech M500s (wired)
- Internet Speed
- 2000/300 Mbps (down/up)
- Other Info
- Arris G36 modem/router
-
- Operating System
- windows 11 26100.3915
- Computer type
- PC/Desktop
- Manufacturer/Model
- homebuilt
- CPU
- Intel I9-13900K
- Motherboard
- Asus RoG Strix Z690-E
- Memory
- 64GB G.Skill DDR5-6000
- Graphics card(s)
- Gigabyte RTX 3090 ti
- Sound Card
- built in Realtek
- Monitor(s) Displays
- Asus PA329C
- Screen Resolution
- 3840 X 2160 @60Hz
- Hard Drives
- WDC SN850 1TB
8TB Seagate Ironwolf
4TB Seagate Ironwolf
- PSU
- eVGA SuperNOVA 1300 GT
- Case
- Lian Li 011 Dynamic Evo
- Cooling
- Corsair iCUE H150i ELITE CAPELLIX Liquid CPU Cooler
- Mouse
- Logitech M500s (wired)
- Keyboard
- Logitech K120 (wired)