I would hazard a guess and say prefetching. SSDs have large blocks, so when you read 1, blocks 2-5 are maybe part of the block and loaded in anyway. Then the co

I would hazard a guess and say prefetching. SSDs have large blocks, so when you read 1, blocks 2-5 are maybe part of the block and loaded in anyway. Then the controller might also cache 6-10 for the heck of it. And 1000+ isn't, so it's not in cache, so it's slower. You might want to try a skipping read test, ie, reading sector 1, sector +10MB, sector +1GB, etc until end of disk, to avoid the controller or OS being able to prefetch data into cache.