Both of these drives are discontinued at retail, but they still show up constantly in used sales, hand-me-down laptops, and “what SATA SSD should I buy” searches because people see the names and assume they’re current. They’re not the same drive at all, and the gap between them matters if you’re actually trying to decide what to put in a system today.
What these drives actually are
The 840 Evo came out in 2013. It used Samsung’s TLC NAND, which was still fairly new at the time, paired with their TurboWrite caching scheme. It got a lot of attention for a bug that caused old data to slow down on reads over time, bad enough that Samsung issued two separate firmware fixes for it in 2014 and 2015. The 860 Evo launched in 2018, five years later, on a more mature 3-bit MLC (TLC) process, with a controller and firmware stack that never had an equivalent public failure.
If you’re shopping used, you’re not really comparing two current products. You’re deciding whether a decade-old drive with a known history of problems is worth buying over one that’s merely old but was solid when new.
Specs side by side
| 840 Evo | 860 Evo | |
|---|---|---|
| Released | 2013 | 2018 |
| Interface | SATA III (6Gb/s) | SATA III (6Gb/s) |
| NAND | 21nm/19nm TLC | 64-layer V-NAND TLC (3-bit MLC) |
| Capacities | 120GB–1TB | 250GB–4TB |
| Sequential read/write | up to ~540/520 MB/s | up to ~550/520 MB/s |
| Known firmware issues | Yes, read-speed degradation bug, fixed via two patches | None of note |
| Endurance (TBW, 250GB class) | ~75TB (varies by capacity) | ~150TB |
| Warranty when new | 5 years | 5 years |
The headline speed numbers look nearly identical, which is the trap. SATA III caps both drives at the same bus limit, so on paper they look like a wash. In practice the 860 Evo holds its write speed more consistently under sustained load and has roughly double the endurance rating at a given capacity, because Samsung’s NAND and controller efficiency improved a lot in those five years.
The 840 Evo’s read-speed bug, explained
This is the part that actually matters for a buying decision. On early 840 Evo units, data that sat untouched for weeks would read back slower, in some cases dropping from ~500 MB/s to under 100 MB/s on affected files. It was tied to how the TLC cells held charge over time and how the firmware refreshed voltage states. Samsung’s fixes added an idle-time background process to rewrite old data periodically. If you buy a used 840 Evo today, you have no way to know whether it ever got the fix applied, or whether a previous owner updated firmware at all. Checking the firmware version against Samsung’s old support pages is possible but tedious, and Samsung’s SSD support infrastructure for this drive is largely abandoned at this point.
The 860 Evo never had anything comparable. That alone is a reason to pay a few extra dollars for one on the used market rather than chase a cheap 840 Evo.
Should you actually buy either one in 2024/2025
Honestly, for a primary drive in anything you depend on, no. Both are SATA drives at this point, and SATA SSD prices have fallen enough that a new drive isn’t a big premium over hunting for a decade-old used one. If you’re filling a SATA-only laptop or an older desktop that doesn’t support NVMe, a new SATA SSD gets you current firmware, a fresh warranty, and NAND that isn’t a decade into its retention life. Flash cells lose charge retention as they age even unpowered, and a used drive that’s eight to twelve years old is NAND that’s been through a lot of program/erase cycles already, regardless of how low the SMART wear counter reads.
Where a used 860 Evo makes sense is a cheap secondary drive, a scratch disk, or reviving an old machine you’re not going to trust with anything irreplaceable. At that point price is the only thing that matters, and you should be comparing it against what a new budget SATA drive costs, not treating “Samsung” as automatically worth a premium. A used 840 Evo I’d avoid outright unless it’s nearly free, specifically because of the firmware uncertainty.
If you’re upgrading anyway
If the system you’re working on supports NVMe at all, even an older PCIe 3.0 M.2 slot, that’s a better use of money than either of these drives. A budget NVMe SSD at a similar price point will outrun both the 840 and 860 Evo by three to five times on sequential transfers and noticeably on boot and load times, since you’re no longer capped by the SATA bus. The only reason to stay on SATA is hardware that physically doesn’t have an NVMe slot, or wanting a drop-in boot drive replacement with zero compatibility questions.
If you do go with either Evo because one landed in your hands for free or nearly free, run a SMART check with CrystalDiskInfo or smartctl before trusting it with anything, and back up to a second location regardless. Age is the real spec here, more than the model number.
