Troubleshooting MemTest86

• Check platform: MemTest86 v5+ images require UEFI. On BIOS-only systems, use the Legacy v4 build (CD/USB/Floppy). Get v4.
• Boot the UEFI entry: open the one-time boot menu (often ESC, F9, F11, or F12) and choose the entry that starts with UEFI: for your USB.
• Recreate the USB with the official imageUSB.exe (Windows ZIP) and verify the download hash.
• Ports & hubs: try a rear I/O port, avoid front-panel hubs; try a USB 2.0 port if available.
• Firmware: disable “Legacy/CSM” if you’re using the UEFI build; update to the latest BIOS/UEFI if boot entries are flaky.

Modern MemTest86 builds are Secure-Boot signed and normally start without changing firmware settings. If blocked:

• Confirm you’re booting the UEFI entry for the USB (not legacy/CSM).
• On Macs with the T2 security chip, reduce boot security per Apple’s instructions, then restore defaults after testing.
• As a last resort, temporarily disable Secure Boot, complete testing, then re-enable.

• Recreate the USB with the official tool and try another port.
• Clear “Fast Boot” in firmware; some boards skip USB scanning with it enabled.
• Set firmware to UEFI-only (or use v4 if the board is truly BIOS-only).
• Update motherboard BIOS/UEFI to improve boot compatibility.

• Ensure the USB has writeable space; MemTest86 can save HTML and optional JSON logs to the boot media.
• When the run completes, follow on-screen prompts to save results. Then mount the USB in Windows to access them.

• Disable XMP/EXPO and test at JEDEC defaults.
• Test each DIMM one-by-one; swap slots to rule out slot issues.
• Update BIOS/UEFI; memory training fixes are common in vendor releases.
• If a module fails across slots, document the report and replace/RMA the stick.

Use imageUSB.exe → Reformat USB (or “Zero USB drive” then replug and format). This resets partitions and restores full size.

Use Etcher (GUI) or dd:

• sudo dd if=memtest86-usb.img of=/dev/sdX bs=4M status=progress conv=fsync (replace sdX)
• On Macs, hold Option at power-on to pick the USB. (Apple Silicon Macs aren’t supported.)

• Reinsert the USB into a **rear I/O port** (direct to motherboard) and avoid hubs.
• Open **Disk Management** → delete all partitions on the USB → create a new simple volume → format **FAT32** → re-run imageUSB.exe.
• Try another USB stick (some controllers misbehave with raw image writes).
• Disable aggressive USB power saving: **Device Manager** → USB Root Hub → Power Management → uncheck “Allow the computer to turn off…”.

• Re-download from the **official page** only. Avoid mirrors or repacks.
• Verify in PowerShell: Get-FileHash .\MemTest86.zip -Algorithm SHA256 and compare to the value on your download page.
• Turn off download “accelerators” or proxies that mangle archives.
• If you use corporate antivirus, extract to a whitelisted folder (AV sometimes quarantines bootable images).

• Use a **wired USB keyboard**; some wireless receivers need BIOS/UEFI “legacy USB”/HID options enabled.
• Try a different USB port (rear panel). Avoid KVMs or hubs during testing.
• Update motherboard **UEFI**; older firmwares have USB HID quirks.
• Note: most runs are **automatic**—you can let it proceed without input.

• Recreate the USB and **reboot cold** (fully power off, wait 10 seconds).
• Disable **XMP/EXPO** and test at JEDEC stock; remove any CPU/RAM overclocks.
• Test with **one DIMM at a time**; swap slots to check for slot issues.
• Make sure fans are unobstructed; overheating can cause system hangs.

Some patterns are **platform-dependent** and may be skipped if the firmware or memory controller doesn’t expose the required features or if stability safeguards are triggered. This is normal and doesn’t indicate a fault by itself.

• Update to the **latest UEFI** and re-test.
• Return RAM to **stock timings/voltages** and try again.

DIMM slot mapping varies by vendor and can be hidden by firmware. To isolate:

• Test **one module at a time** and note the slot used (A2/B2 etc.).
• Swap the suspect module to another slot; if errors follow the module, it’s the **stick**; if errors stay in slot, it’s the **slot/board**.
• Consult the motherboard manual for the vendor’s slot naming.

• Manually step down to the **next lower memory multiplier** or loosen tCL/tRCD/tRP by one bin.
• Increase **DRAM voltage** slightly within spec (e.g., DDR4: up to ~1.37–1.40 V if safe per vendor; DDR5 often 1.25–1.35 V).
• Update to the latest BIOS with **memory training** fixes; check vendor QVL for validated kits.

• Windows with **BitLocker**: suspension may be required before changing boot flow; re-enable afterward.
• Intel Macs with **T2**: reduce boot security and allow external boot; restore defaults after testing.
• Apple Silicon (M-series): not supported for direct boot.

No. Run MemTest86 on **bare metal**. Hypervisors abstract memory and can mask hardware faults.

• Connect directly to the **GPU’s primary output** and avoid adapters during testing.
• Try another monitor temporarily; some EDID/firmware combos report odd modes during pre-OS boot.

• Use a **freshly written** USB and ensure there’s free space on it.
• If logs still don’t write, recreate the USB and try another stick; some older drives expose weird partitions after imaging.
• As a fallback, **photograph** the on-screen summary so you don’t lose evidence.

• Use the **one-time boot menu** instead of changing permanent order for the test run.
• If settings won’t save, replace the **CMOS battery** (common on older boards).
• Save & exit with the vendor’s recommended hotkey; avoid power loss during save.