This theory is not restricted to DRAMless SSDs and not current. Explaining in the most basic of terms, it relates to how information is saved and deleted from pages and blocks as the SSD fills past, for the most part, the 80% mark. Overprovisioning and Garbage Collection which is present in all SSDs counters this. We discuss that in detail in our Beginners article, Trim and Garbage Collection. I would invite you to return with a link if you have found something other than this. We have not, and don’t find it necessary to fill a drive in order to dedtermine if it slows which, actually also brings up another thought which is present in all SSDs, steady state transfer. All SSDs will slow to a certain speed for large transfers; this is inevidable. It is not the result of the drive being half full, and is not restricted to DRAMless SSDs.