Blackmagic Speed Test write speeds plummet

Testing a number of internal SSDs in various Mac computers, many of them show write speeds steadily dropping lower and lower as Blackmagic Speed Test continues to run, starting even within the first minute or two. Is this a sign that the SSDs are defective? Thanks!

I believe many SSDs have fast caches to make them speedy for frequently used files. Speed test will intentionally max out such a cache. So the real SSD speed will start to become clear.

There are probably other reasons this can happen but the cache thing is the most common and doesn’t indicate a failing SSD.

While I don’t see that here with current Macs, get a software called DriveDX to check health of drives.