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The MPS bug on AMD motherboards NEVER ends!

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In 2021, ComputerBase reported that WD SN850 had a low speed on M.2 slots from AMD X570 PCH. It turned out that there was a limit at 128-bytes for Maximum Payload Size (MPS) on AMD X570 MBs and SN850 suffered from it. WD fixed the bug for SN850 in that time.

But a thread on NGA forum shows that things don't end so easily.

In that thread, the poster said that not only X570, but B550 MBs have the same bug as well. The poster used a Hynix PE6031 3.2T on MSI MPG B550 Gaming carbon WIFI's PCH (I get these models from his/her pc components list) and it suffered a seq. write speed downgrade ( just like what SN850 did on X570 PCH ) about 800MB/s.

In another thread on NGA forum another user told why things happen: the MPS on AMD PCHs is limited to the lowest one. And since the MPS of Intel AX210 Wi-Fi card is just 128-bytes, most AMD MBs with Wi-Fi 6 have the problem with some NVMe SSDs.

The list of affected SSDs have known includes Samsung 970 EVO PLUS (older version) , WD SN850/SN750, Zhitai TiPro7000, Hynix PE6031. WD and Zhitai update FWs for SN850 and TiPro7000 to fix the bug, but the poster said that a newer version of SN850 had the same bug again.

Things would only end after AMD fixes the MPS limit rules or ALL SSD manufactuers affected upgrade FWs for their SSDs. But the latter will never come ture becasue the list may be too long and some SSDs have lower seq. write speed are for DC/enterprise use.

So AMD should launch a new PCH driver to fix it soon.
 
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To clarify, this does not affect direct-to-cpu (aka fastest) M.2 slot?

Also, does this affect drives of all speeds, or just the fastest ones?
 
Joined
Aug 11, 2021
Messages
37 (0.09/day)
Location
Wuhan,China
To clarify, this does not affect direct-to-cpu (aka fastest) M.2 slot?

Also, does this affect drives of all speeds, or just the fastest ones?

Yes, things only go wrong on AMD chipsets.
I think just some particular NVMe SSDs are affected by a low MPS limit, regardless of speed essentially. But only faster types show the downgrade clearly.
 
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