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Threads - The number of tasks which the OS's scheduler can schedule. Think of them as workers. A program can request more workers in order to complete a task faster
PCI Express Lanes - The number of electrical PCI Express connections between two components.
Bandwidth - The amount of data which can flow between two components.
The CPU has a small number of PCI Express lanes which are used to interconnect through the motherboard, especially between the CPU and external chipset, and the rest are divided up however the manufacturer decides, be it SATA ports, an M.2 slot, external PCI Express, or a combination of the three. The chipset itself has a number of PCI Express lanes, and the X370 is the only one with enough to power a PCI Express 3.0 x8/x8 setup, which is plenty for dual graphics cards.
I always explained it like this.
Think of it as destinations.
PCI-E, SATA, M.2, CPU
The PCI lanes are exactly that, lanes. They get you from destination A to destination B.
Threads relate to CPU. How many different work centers are at that destination.
Bandwidth is the size of the BUS. How many people can the bus fit.
Alright. I feel I have a grasp on what lanes are and how they work. However, would a single gpu take up all 16 lanes of the R7? And then the chipset handles the sata, m.2 and so forth?
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The motherboard manufacturer determines how the PCIe lanes are divvied up. Take the ASUS Strix X370-F for example:
The board has 3 PCIe x16 physical slots, and 3 PCIe x1 physical slots. With a Ryzen processor, one of those PCIe x16 slots will run at full x16 if one is populated, or two at x8 if both are populated, the third will always run at x4, or less if two of the PCIe x1 slots are populated. PCIe is not dynamically allocated, so you can't have something like x10/x6, so if you just use one graphics card, the second slot is essentially unpowered with the GPU getting all 16 lanes.
On that board, the M.2 slot does not share bandwidth with SATA slot, so it will run with its 4 dedicated lanes.
Ah. That clears it up. Thanks! Let's take it one more step though... Let's say I have 1 gpu running with all 16 lanes in a PCI e x16 slot and I decide to add a sound card into one of the PCIe x1 slots. According to the image above, the chipset will take those lanes instead of the CPU?
Yes, the x1 slots are added by the chipset connectivity.
This may be a little off.
If you are gaming, I would get a single GPU.
Also a bigger M.2 SSD will hugely benefit you in the future. 120GB will fill up super quickly.
This is what I'm working with:
-Ryzen 7 1700x
-NZXT Kraken X62 Cooler
-Asus Strix X370-F Mobo
-G.Skill DDR4-3200MHz RAM
-Corsair 120GB M.2 SSD
-WD 1TB HDD
-Corsair HX750i PSU
..As for GPU, I currently have Asus Strix GTX 1050 ti (got it dirt cheap and only have a 1080p TV.. QHD, 144hz monitor to come). Future plan is to run 2 GPU's of GTX 1080, RX Vega, or equivalent...most likely Vega.
I was thinking the same with the single GPU, its a want rather than a need. Also, the M.2 is strictly for OS and a few content creation applications. 128GB fits my needs for this. A 1 TB SSD will be added as necessary down the line.
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