Seems that the Samsung 840 Evo is notorious for performance degradation. : r/buildapc
SAMSUNG 840 Series 2.5" 250GB SATA III TLC Internal SSD - Newegg.com
Samsung 840 Pro SSD Review | TechSpot
SAMSUNG 840 EVO MZ-7TE250BW 2.5" Internal SSD - Newegg.com
Amazon.com: New A+ Samsung SSD HDD 840 PRO 2.5" 7mm 128GB MZ-7PD128BW MZ7PD128HCFV-1BW00 0Z000 SATA 3.0 6.0Gb/s MLC Hard Disk Solid State Drive Laptop : Electronics
Samsung SSD 840 Pro Review - StorageReview.com
Samsung 840 Pro 128GB SSD Review | TweakTown
Samsung 840 series review: High-end entry-level SSDs - CNET