MemTest86 vs MemTest86+: Differences and Which One Is Right for You?

If you've ever experienced random crashes, screen freezes, or data corruption, memory is probably the culprit, and you've come across these two tools: MemTest86 and MemTest86+. the RAM tests par excellence to validate modules and platforms, and although they share origins, they now follow different paths.

Before choosing, it's a good idea to understand their differences, how they work, and what tests they perform. In this comparison guide, you'll find a complete and updated vision, from history and licensing to UEFI/BIOS compatibility, testing algorithms, system integration, and advanced professional features.

What are MemTest86 and MemTest86+

Both utilities serve to check the integrity of the RAM memory subjecting it to intensive read/write patterns outside the operating system. They run as standalone programs from a storage medium Boot, allowing direct control of the hardware and preventing the OS or cache from mask errors.

MemTest86 was born in 1994 by Chris Brady and, after years as a reference, was acquired by PassMark in 2013. Since version 5.0 it has incorporated UEFI boot, mouse-based graphical interface and Secure Boot support, and added modern tests such as "row hammer", in addition to DDR4/DDR5 compatibility in recent editions.

Origin, bifurcation and evolution

During the early 2000s the original MemTest86 branch was stopped (it was left at v3.0 in 2002), and in that gap appeared Memtest86 +, the fork driven by Samuel Demeulemeester to support Newer CPUs/chipsetsThis fork maintained the original philosophy, updating compatibility and fixing bugs.

With There, MemTest86 has evolved under PassMark with a "freemium" model (free edition and paid Pro edition with extras for laboratory), while Memtest86+ has remained as a project open source (GPL). In October 2022 it was rewritten to the 6.x branch to support UEFI and DDR4/DDR5 memories, and in February 2023 it was already at version 6.10 with support for current chipsets and CPUs.

Licensing and distribution model

Memtest86+ continues under GNU GPL v2.0 license, which allows free downloading, modification, and redistribution. It's the preferred option if you value free software and inclusion in distros. Linux and code transparency.

MemTest86 (PassMark) adopts a free scheme versus Pro/Site. The Free edition covers general needs, but paid editions provide professional utilities such as DIMM/chip decoding, SPD validation, ECC error injection, automation by configuration file and integration with logic analyzers, among other functions oriented to SATs and testing laboratories.

Compatibility, platforms and firmware

On modern platforms, MemTest86 runs from UEFI (the v10 is UEFI only) (consultation How to adjust memory from UEFI or BIOS). If you need legacy BIOS support, v4.3.7 remains available for legacy scenarios (included in downloads as "Older Versions"). In addition, it supports Windows, Linux and macOS as host platforms to create the boot media.

Memtest86+ 6.x supported UEFI and BIOS, which makes it especially useful for older and current computers. It is also integrated into distributions such as Debian, Ubuntu, and Arch Linux (BIOS mode from GRUB), with patches to maintain functionality and compatibility over the years in the GNU/Linux ecosystem.

Method of execution and creation of the medium

These tools run without an operating system: you prepare a USB/CD and boot the computer from that media. This approach allows the tester to reserve as much RAM as possible possible and directly access the hardware, raising the reliability of the diagnosis.

The typical flow is simple: you download the appropriate image, burn the USB with utilities like Rufus, Etcher or the official installer, and select the boot from USB in the board menu. Once loaded, the test starts automatically and runs multiple passes with varied data patterns.

Quick Start Guide: USB Creation and Options

In MemTest86 (PassMark), you download a .zip package with a tool to write the image to the flash drive. After booting, you'll see a menu with options such as System Info, Test Selection, RAM benchmark and fine-tuning. The UEFI interface is graphical and mouse-friendly, making it easy to use. the navegation.

Memtest86+ has a Windows installer that automates the process: choose the USB drive, accept formatting, and the bootable media is created. On very old computers, you can also use CD or floppy disk, although USB is clearly recommended these days. If your BIOS won't boot from USB, check the boot order or use the appropriate firmware version.

How memory tests work

The methodology consists of writing specific patterns to all memory addresses and verifying that when reading there are no discrepanciesThis detects defective cells, addressing errors, interference problems, and intermittent data- or temperature-dependent failures.

Memtest86+ details a battery of extremely effective classic tests. A standard run covers tests 0 through 8, and test 9 ("bit fade") is manually activated. Execution is cyclical and infinite, so you can leave it for hours to increase statistical confidence.

Test details (Memtest86+ 0–9)

• Test 0 – Address test, walking ones, no cache: It walks through all addressable bits in a "walking ones" pattern through all banks, identifying addressing errors.
• Test 1 – Address test, own address: write the own address in each cell and checks for differences. It is more stringent than Test 0 and is complementary to locating addressing errors.
• Test 2 – Moving inversions, ones and zeros: Fast algorithm that alternates 1s and 0s; often uncovers faults in memory subsystems badly damaged.
• Test 3 – Moving inversions, 8-bit pattern: designed to detect errors by interference between adjacent cells.
• Test 4 – Moving inversions, random pattern: Same as 3, but with pseudorandom number and its complement; uses ~60 different patterns per pass, so multiple passes increase efficiency.
• Test 5 – Block move, 64 moves: It uses block copy instructions (movsl) based on the old "burnBX". It usually uncovers subtle errors.
• Test 6 – Moving inversions, 32-bit pattern: slower, but very effective after 32 pattern passes; detects data errors difficult.
• Test 7 – Random number sequence: writes random numbers, complements them and checks them again. It can surface intermittent faults.
• Test 8 – Module 20, ones and zeros: "Modulo-X" algorithm designed to minimize the impact of caches that could hide errors in previous tests.
• Test 9 – Bit fade (90 min, 2 patterns): Initializes all RAM, leaves it idle for 90 minutes, and checks for variations. It runs twice (all 0s and all 1s) and lasts ~3 hours; it is not in the standard cycle and must be activated manually.

Please note that tests 4 and 7, due to their random nature, may bring to light CPU instabilities In addition to RAM, this is why multiple passes are advisable: each iteration uses different patterns that increase coverage.

Advanced Testing, UEFI and SIMD

The modern branch of MemTest86 integrates additional tests into UEFI, including row hammer detection and numbered tests. #11 and #12 that use SSE/Neon instructions to move 64/128 bits per operation. These modes strain the bandwidth and data paths, useful for discovering errors under high pressure.

In addition, the UEFI interface provides compatibility with Secure Boot and improved peripheral support (e.g. USB keyboards on systems that do not properly emulate certain IO ports), making it easier to interact across platforms most recent.

Exporting Errors and BadRAM

Since MemTest86 2.3 and Memtest86+ 1.60 both tools can generate a list of bad regions in a patch-compatible format. BadRAM of the Linux kernel. GRUB2 allows this information to be injected even without patching the kernel, which makes it unnecessary BadRAM in many cases.

Windows offers something similar via "badmemorylist/badmemoryaccess," but it requires manual conversion. Clicking here helps integrate with systems. isolate bad blocks and keep a machine operational while managing damaged hardware.

Pro Features and Lab Utilities (MemTest86)

In professional environments, MemTest86 Pro adds capabilities such as DIMM/chip decoding to map a failed address to a specific physical slot (depending on hardware), SPD validation, automation by configuration file, and support for logic analyzers (for example Keysight U4164A) through error triggers.

It also incorporates ECC error injection to validate correction and reporting mechanismsSupport depends on the CPU/chipset/BIOS and, for some AMD retail models, may be disabled by default; it's a key tool for SATs and validation. post-assembly.

CPU and core compatibility

Both branches support modern x86 architectures with multicore. MemTest86 Free employs up to 16 cores and the Pro edition scales up to 512, while Memtest86+ has been updated to work with CPU Intel and current AMD, including DDR4/DDR5 in its 6.x rewrite.

As a note, ECC reporting on ARM is not supported in MemTest86 and certain functions (such as DIMM decoding and timing recovery from BIOS/SMBIOS) are dependent on chipset and exposed tables, so the availability varies.

ECC Error Injection: Supported Chipsets (MemTest86)

La ECC injection It allows you to simulate failures to verify system error handling. Compatibility depends on hardware/BIOS and covers a wide range of AMD and Intel platforms across multiple generations.

• AMD: Bulldozer/Steamroller/Jaguar/Ryzen (17h–1Ah; usually disabled in retail), Steppe Eagle SoC, Merlin Falcon SoC
• Intel: Nehalem, Lynnfield, Westmere, Core 2nd–13th Gen and Xeon E3/W/Scalable equivalents, including mobile (Tiger Lake-H) and SoC (Silvermont, Apollo Lake, Elkhart Lake) series, as well as W-2400/3400

The goal here is to validate that the stack (controller, ECC, firmware and system) responds correctly to error conditions, something critical in production and data centers.

Test execution and duration tips

The recommended duration is "as many passes as your level of skill allows." The tests are infinite, and leaving it for several hours increases the likelihood of encountering intermittent or data/temperature-dependent errors. Test 9 ("bit fade") adds another layer after leaving the RAM inactive 90 minutes.

If red lines appear on the screen (reported bugs), the module is probably faulty. On computers with multiple DIMMs, test each module and each slot separately, because a failure can be due to baseboard or channel in addition to the stick itself.

Factors that can alter the results

RAM is sensitive to physical and environmental variables: thermal fluctuations, interference, power supply and "soft errors" by cosmic rays or small radioactive sources in materials. It's not science fiction: it's documented by IBM's technical literature, and its impact on reliability it is not negligible.

Thermal errors: These sometimes appear after the 3rd or 4th pass due to overheating. Ensure proper ventilation over the DIMMs, and even active ventilation if you were to do so. prolonged stress tests. On overclocked systems, lower frequency/voltage to stable values ​​before concluding that the RAM is damaged.

Interferences, feeding and false positives

Although it is rare today, there may be mutual/external interference that degrades signals at certain MHz. Also, feeding anomalies (unstable power supply or dirty mains) generate false positives; monitor PSU voltages during testing.

When using mixed kits or memory from different manufacturers/latencies/voltages, the chances of instability increase. Ideally, the modules should be identical in specifications; mixing batches can complicate diagnosis and XMP/EXPO profiling.

Linux integration and boot options

Memtest86+ is part of multiple Linux distros (Debian, Ubuntu, Arch) and appears in the GRUB menu in BIOS installations, making it easy to run a test. without downloading anything additional. These distros have maintained patches to keep legacy code functional with new versions of tools and compilation strings.

MemTest86, for its part, continues to offer updated images and compatibility with macOS as a platform for generate the USB. In UEFI, it supports Secure Boot and modern peripherals, which is handy on recent hardware.

When to use each

If you are looking for a free, BIOS/UEFI compatible and very up-to-date option for modern hardware, Memtest86+ 6.x is a great option. solid betIf you need professional features (ECC injection, DIMM decoding, automation, integration with instrumentation), MemTest86 Pro offers a set of tools hard to match.

For the home and enthusiast user, the free edition of both is usually sufficient. Still, on modern UEFI, MemTest86 Free provides a polished interface, Secure Boot, and advanced testing, while Memtest86+ stands out for its BIOS/UEFI scope transversal and its presence in Linux distributions.