When Windows won't boot at all.
A Buildroot-based minimal Linux image that boots straight into a full-screen diagnostic tool — no login prompt, no OS install needed, straight into diagtool.
RAM test — 128 passes, five algorithms.
Each algorithm catches a different real fault class, the same way Memtest86/memtester splits its own test suite.
Illustrative sample data.
RAM test
5 algorithms: address test, moving inversions (solid and random), walking ones, block sequential. A continuous mode loops the whole battery indefinitely with a live pass/error counter.
CPU stress test
3 algorithms loading different execution units: integer checksum, floating-point reduction, memory bandwidth.
GPU test
PCI-based GPU detection plus a framebuffer/VRAM pattern test — the most a driver-less diagnostic image can honestly do, and it says so.
Disk test
SMART health query plus a read-only sequential throughput benchmark — deliberately never a write test.
Configure before you run.
A dedicated test configuration screen lets you toggle any individual algorithm on/off, adjust thread counts, durations, and the disk device path — all before running. Big ASCII-art PASS/FAIL/ERROR banners after every test make the outcome unmistakable at a glance.
A real bug the GPU test found in QEMU.
The first version of the framebuffer pattern test, run against a virtual GPU, reported hundreds of false "VRAM errors" — not a real fault, but a race with the kernel's own console driver, which keeps redrawing text and a blinking cursor into that same framebuffer independently of the test. Fixed by switching the console to graphics mode for the duration of the test, then back afterward — the same mechanism old X servers used to take over the display. Re-verified clean: PASS, 4,096,000 bytes of VRAM tested, no errors, against the same virtual GPU that produced the false positives before the fix.
From the desktop app to the USB stick.
USB Creator is a Rufus/balenaEtcher-style tool built into the desktop app, with three independent safety checks before it ever writes a byte.
Every angle on instability
When the desktop app can't even boot, this is the last line of diagnosis.