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ok so the ssd is running slow because it is for some reason in pcie 2x4 mode and not pcie 3 even though its in a x16 slot, idk how to change it though
Transfer mode is x4 PCIe 2.0 which is typical for the CHIPSET on a B450-based board. Adapter has no impact on this as you're bottlenecked by the chipset/PCH.

PCIe 2.0 transfers at 5 GT/s per lane, so 20 GT/s in this case, and considering 8 bits/byte and 8b/10b encoding that comes out to 2 GB/s. Overhead is at least 10%, so 1.8 GB/s at the most is expected. That would be at maximum queue depth and thread count, keeping in mind the entire chipset bandwidth is limited to that amount, which likely includes other devices (e.g. SATA).

The primary M.2 slot uses CPU lanes and would thus run at x4 PCIe 3.0. An adapter will only hit those speeds using CPU and not chipset lanes - which would mean no discrete GPU.
 

kamikazilucas

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Transfer mode is x4 PCIe 2.0 which is typical for the CHIPSET on a B450-based board. Adapter has no impact on this as you're bottlenecked by the chipset/PCH.

PCIe 2.0 transfers at 5 GT/s per lane, so 20 GT/s in this case, and considering 8 bits/byte and 8b/10b encoding that comes out to 2 GB/s. Overhead is at least 10%, so 1.8 GB/s at the most is expected. That would be at maximum queue depth and thread count, keeping in mind the entire chipset bandwidth is limited to that amount, which likely includes other devices (e.g. SATA).

The primary M.2 slot uses CPU lanes and would thus run at x4 PCIe 3.0. An adapter will only hit those speeds using CPU and not chipset lanes - which would mean no discrete GPU.
but the motherboard says both 16 slots are pice 3
 

kamikazilucas

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Transfer mode is x4 PCIe 2.0 which is typical for the CHIPSET on a B450-based board. Adapter has no impact on this as you're bottlenecked by the chipset/PCH.

PCIe 2.0 transfers at 5 GT/s per lane, so 20 GT/s in this case, and considering 8 bits/byte and 8b/10b encoding that comes out to 2 GB/s. Overhead is at least 10%, so 1.8 GB/s at the most is expected. That would be at maximum queue depth and thread count, keeping in mind the entire chipset bandwidth is limited to that amount, which likely includes other devices (e.g. SATA).

The primary M.2 slot uses CPU lanes and would thus run at x4 PCIe 3.0. An adapter will only hit those speeds using CPU and not chipset lanes - which would mean no discrete GPU.
so if i made it so my gpu used 8 lanes instead of 16 i would have more cpu lanes to use on my ssd and then i can make it run at full speed ?
 

kamikazilucas

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You can put graphics card into second PCIE x16 slot (PCIE 2.0 x4) and
put PCIE M.2 adapter into top PCIE 3.0 x16 slot.

You'll get full speed on your M.2 drive this way. Graphics card bandwidth will suffer a bit though.
yeah i could but when i get a new gpu which i am gonna soon it will bottleneck it alot
 

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yeah i could but when i get a new gpu which i am gonna soon it will bottleneck it alot
GPU on x4 PCIe 2.0 is definitely pushing it a bit. TPU tested this with a 2080 Ti and found ~20% drop in FPS.

ok thanks, idgi why dosent the new cpus have more than 20 lanes, they litterally only give you enough for 1 gpu and ssd and thats it
It's a B450 limitation. B550 and X570 would be fine, assuming an appropriate CPU. To be fair, your limitation isn't a big deal with the 1TB P2.
 

kamikazilucas

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GPU on x4 PCIe 2.0 is definitely pushing it a bit. TPU tested this with a 2080 Ti and found ~20% drop in FPS.



It's a B450 limitation. B550 and X570 would be fine, assuming an appropriate CPU. To be fair, your limitation isn't a big deal with the 1TB P2.
are b550 chipset lanes pcie 3 or 4?
 

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