>>I had 2 x 500Gb Samsung SSD that I took out of an old server and wanted to sell. The potential buyer tested them and said they were no good with read speeds of only 3Mb/sec !! So I researched the problem and found that first I made the mistake of trying to full-format them and secondly they had been in use a long time even with TRIM on. I purchase a program called Parted Magic https://partedmagic.com which is a disk management tool with many features. It comes as an iso which you have to burn onto a DVD and then boot off that DVD. Then I plugged in the 2 SSD into a USB drive enclosure and plugged them into the computer. Then did a secure erase on them which took just 1 minute. The drives went back to having access speeds of > 30Mb/sec as per spec.
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>Hopefully you meant the speed went up to > 300 MB/sec ; 30 MB/sec is slow even for a mechanical hard drive.

Sorry, yes, typo. It was a 10 fold increase in access speeds binging the drive back to expected performance.