Samsung 870 EVO Not Detected, Not Booting, Disconnecting, Slow Speeds, and Bad Block Problems

Samsung 870 EVO Not Detected, Not Booting, Disconnecting, Slow Speeds, and Bad Block Problems

The Samsung 870 EVO usually fails in ways that make the drive look only partly broken. It may appear in BIOS but not in the boot list. It may show up briefly in Samsung Magician and then disappear again. It may finish a clone successfully, yet the first boot ends at the Windows logo with a blank screen. It may benchmark at only half the expected speed because the drive has negotiated the wrong SATA mode. 

In the worst cases, the 870 EVO keeps a nearly normal health reading while the system starts logging bad blocks, freezing, or treating the drive as read-only. Those split failures are what make this page different from a generic not working or not recognized complaint.

Problem: The 870 EVO appeared briefly in Samsung Magician, then disappeared or could not be migrated

What users observed: One exact 870 EVO migration case started with the drive showing up in Samsung Magician, but with no usable drive data. As soon as the user refreshed the app or tried to start migration, the SSD disappeared again. The drive also failed to stay visible in Device Manager and Disk Management, which made the problem look like a dead SSD even though the same drive still appeared intermittently in UEFI.

What was tried: Users first stayed with the same SATA-to-USB adapter and kept retrying Magician, refresh, reconnect, and migration. They also assumed the adapter path should be enough for a normal clone because the drive could at least be seen part of the time.

How this played out: The migration only worked after the 870 EVO was moved off the bad SATA-to-USB adapter and connected directly inside the PC with normal SATA data and power. In the solved case, borrowing the SATA and power leads from the DVD drive long enough to complete migration was what made the drive behave normally. This was not fixed by another Samsung Magician refresh or another USB reconnect. The unstable adapter path was the real blocker.

Problem: The cloned 870 EVO showed the Windows logo and then only a blank screen

What users observed: In a solved clone case, a Windows installation was cloned from an older Samsung SSD to a new 870 EVO and the copy process completed without obvious errors. After the swap, the laptop reached the Windows logo, then stalled on a blank screen with a movable cursor. That made the clone look almost successful, which is exactly why this problem wastes time.

What was tried: The old drive was already disconnected on first boot, so the usual “disconnect the original drive” advice had already been satisfied. The user had also cloned over USB, which is where the problem narrowed itself.

How this played out: The solved outcome was to avoid that USB-to-SATA cloning path and repeat the clone using a different adapter or, better, with both drives connected directly over SATA inside a desktop. In the reported case, the USB adapter’s partitioning behavior was treated as the reason the cloned 870 EVO would not boot properly once installed internally. When the cloning path changed, the boot failure stopped looking like a bad SSD and started behaving like a bad migration method.

Problem: The SSD was installed, but it did not show up as a usable boot device in BIOS

What users observed: Another class of 870 EVO complaints starts with the drive being physically present and even visible in storage menus, but missing from the actual BIOS boot list. That makes the drive look inconsistent: the board knows something is there, but still refuses to treat it as a normal boot target.

What was tried: Users swapped only the SATA data side first, checked ordinary BIOS screens, and retried boot priority without changing the power lead or the board’s SATA boot behavior. In older systems, that often left the same exact symptom in place.

How this played out: In one solved case, the missing-boot-target problem cleared only after Use RST Legacy OROM was enabled in BIOS, which made the SSD appear again in boot priority. In another solved detection case, simply changing to a different SATA power connector restored normal drive detection. On this class of SATA SSD, both are real, narrow fixes: one at the BIOS boot-mode layer, the other at the power-delivery layer.

Problem: The 870 EVO kept disconnecting or disappearing after a few minutes of use

What users observed: A newly installed 870 EVO could look healthy at first, then drop off the system during ordinary activity such as game installs or heavier file writes. In one solved case, the drive passed Samsung’s own diagnostic check, yet kept disappearing after only a few minutes of use. That made the failure look random and much harder to trust.

What was tried: Users checked the SATA port choice and initially focused on bandwidth-sharing assumptions, because the drive had been installed in a port that should have worked on paper. The drive was left in place while repeated disconnect behavior continued.

How this played out: The solved advice was to update the motherboard BIOS, and in that case the disappearing behavior was treated as a board-level compatibility issue rather than a dead 870 EVO. This is one of the more useful real-world outcomes because the SSD did not fail in a clean, permanent way. It behaved like a compatibility problem until the board firmware path was corrected.

Problem: 870 EVO working very slowly

What users observed: Users reported 870 EVO read and write speeds in the rough 250 MB/s range instead of the normal SATA 6 Gb/s performance they expected. CrystalDiskInfo showed the crucial clue: the drive had negotiated SATA/300 instead of SATA/600. That made the SSD feel underwhelming even though it was not actually broken.

What was tried: The drive was first left on the same internal connector path while users checked firmware and compared performance to other storage already in the machine. Keeping the 870 EVO on that same cable path changed nothing.

How this played out: Full performance returned only after the 870 EVO was moved to a different SATA connection path that allowed it to negotiate SATA/600. In the solved laptop case, changing where the drive was connected instantly raised performance into the normal 500+ MB/s range. The issue was not the SSD firmware, the OS, or Windows 11. The drive had simply been sitting on the wrong SATA path for full speed.

Problem: The drive started showing bad blocks, became inaccessible, or slipped into read-only behavior

What users observed: The more serious 870 EVO failures often begin with disk I/O errors, uncorrectable read behavior, or a drive that still appears in Windows but can no longer be opened, formatted, erased, or repartitioned. In other reported cases, users saw the drive degrade into system freezes, boot issues, or eventual 0-byte detection. One reason these failures are especially dangerous is that the visible health number can stay deceptively high even while the real read path is already collapsing.

What was tried: Users tried the usual storage-recovery habits first: format attempts, partition removal, fresh system changes, and general software-side checks. Those attempts did not restore normal access once the drive had crossed into bad-block or inaccessible behavior.

How this played out: The real outcome in these cases was not a software repair. Once the 870 EVO began showing bad blocks, write-protect behavior, freezes, or inaccessible sectors that survived reboot and format attempts, the practical fix was to stop trusting the drive, copy whatever readable data remained, and replace or RMA it. In cases severe enough to produce 0-byte behavior or persistent uncorrectable read failures, the drive had already moved beyond a normal not detected or boot issue and into outright hardware failure.