Question Ssd slower in second m.2 slot?

shabby

Diamond Member
Oct 9, 1999
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Just got a pcie gen 4 ssd and noticed in the top slot i get 7.4gb/sec read and 6.6gb/sec writes while in the lower slot i get 6.6gb/sec read and only 3.2gb/sec write. Is this because the top slot gets its pcie lanes from the cpu and the bottom slot from the chipset? Its an asus x570 mobo.
 

deustroop

Golden Member
Dec 12, 2010
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If the on and off CPU lanes are the same generation then you will notice a performance difference only if your application is sensitive to PCIe latency.


I wouldn't think a difference in such minuscule latency will cause a substantial loss of bandwidth like you report.
 

shabby

Diamond Member
Oct 9, 1999
5,760
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I wouldn't think either but it did, only reason i'm using the lower m.2 slot is because the mobo has a heatsink for the ssd and it drops the temps around 10c.

Screenshot_20211219-105245_Gallery.jpg20211219_105540.jpg
 

shabby

Diamond Member
Oct 9, 1999
5,760
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81
I did, that's how I got those two results above. One result is before I put the os on it but when I switched it later it's the same results.
 

KentState

Diamond Member
Oct 19, 2001
8,397
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The lower slot has to share the 4 PCIE lanes back to cpu with everything on the chipset. This includes SATA, USB, nic and so on.
 
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