Legacy • BIOS / CSM • Older PCs

MemTest86 — Legacy BIOS Build (v4)

This page provides the classic v4 release of MemTest86 for systems that do not support UEFI. If your motherboard has UEFI, use the modern build instead. For BIOS‑only machines, choose one of the v4 images below (CD, USB, or Floppy) and follow the quick start.

Download v4 Images

Select your operating system to grab the appropriate images. All v4 builds are designed for Legacy BIOS/CSM boot.

Windows — CD Image Burn to CD/DVD, then boot via BIOS/CSM

ISO Older PCs

Download

Windows — USB Image Write image to USB drive, boot via BIOS/CSM

IMG Legacy

Download

Windows — Floppy Image For very old systems with floppy drives

IMG

Download

Linux / Mac — CD Image Burn to CD/DVD, then boot via BIOS/CSM

ISO Linux / macOS

Download

Linux / Mac — USB Image Use dd/Etcher to write image, then boot via BIOS/CSM

IMG macOS

Download

Linux / Mac — Floppy Image Legacy media for very old systems

IMG

Download

When to choose v4

Your motherboard does not support UEFI and boots using Legacy BIOS / CSM.
You need MemTest86 on very old PCs, or to troubleshoot pre‑UEFI platforms.
You prefer simple, proven diagnostics for hardware from the BIOS era.

Requirements

Legacy BIOS/CSM capable motherboard
USB drive ≥ 512 MB (for USB image) or blank CD/DVD (for ISO)
Another PC to write the media (Windows, Linux, or macOS)

Quick Start

Download the appropriate image for your OS (CD/USB/Floppy).
Write the image to media (e.g., Rufus / Etcher / dd).
Boot the target PC, press the BIOS boot key, and select your media.
Run several passes; if errors appear, test modules one‑by‑one.

Verify integrity

Compare the SHA‑256 hash from the download page with your file before booting.

Windows PowerShell: Get-FileHash .\memtest86-v4.img -Algorithm SHA256

Important

v4 targets BIOS/CSM systems only. If your board supports UEFI, prefer the modern UEFI build for better hardware support and features.

Troubleshooting

USB not detected? Try another port, re‑write the image, or switch to CD. Still stuck? Reseat RAM and test modules individually.

Documentation

For usage tips and background, see the main help pages and release notes. Keep notes of any error addresses for later comparison.

Which build should I use?

UEFI build for modern PCs • v4 (BIOS) for older, legacy-only systems

UEFI Build (Recommended)

Best compatibility and features on modern hardware with UEFI firmware.

Secure‑Boot signed; boots from UEFI USB
Modern test patterns and reporting
Works with most Windows 10/11 PCs

Get UEFI Build

Legacy BIOS Build (v4)

For systems that only support Legacy BIOS / CSM (no UEFI option).

Boots via BIOS from CD/USB/Floppy
Simple, proven diagnostics for older PCs
Use when UEFI boot is unavailable

View v4 Downloads

Legacy v4 — FAQ

How do I know if my PC needs the v4 (BIOS) build?

If your firmware setup has no UEFI option and boots only in Legacy/CSM mode, use v4. A quick sign: your boot menu shows legacy drives without the “UEFI:” prefix.

Which boot key opens the BIOS boot menu?

Common keys: F12 (Dell, Lenovo, Gigabyte), F11 (MSI), F8 (ASUS), Esc (HP). Power on and tap the key repeatedly to select your USB/CD.

How do I write the v4 USB image on Windows, Linux, or macOS?

Windows: Rufus (select image → Write).
Linux: sudo dd if=memtest.img of=/dev/sdX bs=4M status=progress conv=fsync (replace sdX).
macOS: Balena Etcher or dd via Terminal. Always eject safely.

How many passes should I run?

At least 4 passes for a quick check; run overnight for intermittent issues. If errors appear, test each DIMM and slot one‑by‑one.

MemTest86 found errors — what next?

Reseat modules, test sticks individually, and consult your motherboard QVL. If a module consistently errors, document with the report and contact your retailer for RMA.

Why not use v4 on a UEFI system?

The modern UEFI build offers better hardware support, Signed Secure‑Boot, and richer reporting. Use v4 only when UEFI isn’t available.