A standalone, bootable RAM tester for PowerPC Macs — a faithful, line-by-line port of memtest86+ v2.00 to Open Firmware. It boots with no operating system, so the maximum fraction of system memory is under test. Same blue-screen TUI, IBM VGA 8x16 font, and green title bar — plus the runtime configuration menu.
vibe-coded with Claude 
Two methods:
Burn and boot memtestppc.iso (hold the c key at the startup chime)
- Copy the ELF binary to your hard drive as
/memtest(right beside/mach_kernel) - Boot into OpenFirmware (hold option + command +
o+fat the startup chime) - Enter
boot hd:3,memtestif using the first partition,boot hd:5,memtestif using the second partition, etc. - Note: this is just a single-shot. When you reboot, OpenFirware will resume using
/mach_kerneland boot into Tiger/Leopard.
v2.00 — a faithful, line-by-line port of memtest86+ v2.00. Boots and runs
end-to-end on real iBook G3 hardware — from a burned CD-R, from an HFS+
partition, and as a QEMU -cdrom image. The full v2.00 test suite cycles with
Errors: 0 on good RAM, the TUI and runtime config menu render and respond, and
CPU / clock / cache / memory all come from Open Firmware.
| Surface | Status | Notes |
|---|---|---|
| memtest86+ v2.00 test suite | ✅ Working | Address, moving-inversions, block-move, modulo-20, and random tests cycle; Errors: 0 on good RAM. |
| Run on real iBook G3 | ✅ Working | Boots + runs via Open Firmware (/memtest, boot hd:3,memtest); PowerPC 750, the 900 MHz iBook. |
| Boot from CD image in QEMU (mac99) | ✅ Working | Via a CHRP boot script; needs ≥128 MB RAM under OpenBIOS. |
| Physical CD boot | ✅ Working | Burned CD-R boots on a real iBook G3. genisoimage HFS hybrid: DDM+APM+blessed tbxi (ofboot.b) with a <COMPATIBLE> block for New World OF. |
| TUI rendering (VGA font, colors, layout) | ✅ Working | Embedded IBM VGA 8x16 font rendered to the OF framebuffer. |
| 8-bit framebuffer + palette | ✅ Working | Real iBook G3 (ATI Rage Mobility); Apple OF color! palette setup. |
| 32-bit framebuffer path | ✅ Working | QEMU's mac99 framebuffer. |
| CPU id (PVR → G3/G4/G5) + clock/cache | ✅ Working | CPU name from the PVR; clock and cache sizes from the OF device tree. |
| Memory discovery + claim | ✅ Working | OF /memory + ofw_claim in 1 MB chunks (~244 MB of 256 on the iBook). |
Runtime config menu (c) |
✅ Working | Test Selection / Address Range / Error Report Mode / Restart / Refresh, driven by OF console keys. |
| Error display (white-on-red) | 🟡 Partial | Full-row red verified in QEMU; not yet triggered on real 8-bit hardware (no errors seen there yet). |
| Bit-fade test | 🟡 Partial | sleep() runs off the OF timebase; selected-only (not in the default pass), so its ~90-min dwell never runs by default. |
Requires a powerpc-linux-gnu cross toolchain, qemu-system-ppc, and
genisoimage (all on a Linux host; Tiger's own gcc can't produce the ELF that
Open Firmware needs).
make memtestppc.iso
# Run in QEMU (mac99; 128 MB+ is required for OpenBIOS auto-boot):
qemu-system-ppc -M mac99 -m 256 -cdrom memtestppc.iso -boot dOn a real PowerPC Mac, burn memtestppc.iso to a CD-R (e.g.
wodim -dao -eject dev=/dev/sr0 memtestppc.iso) and hold C at the startup
chime, or boot it from the Open Firmware prompt with boot cd:,\\:tbxi.
Alternatively, copy memtestppc.elf to an HFS+ partition and
boot hd:N,memtestppc.elf.
src/ — the v2.00 port: head.S, ofw, display, lib, screen_buffer, random,
init, memsize, error, test, config, patn, main (+ test.h,
config.h, font_vga.h, ppc.h, linker.ld).
cd/ — boot script (ofboot.b) + HFS type map (hfs.map) for the ISO.
ref/ — memtest86+ v2.00 source (the port's base) + v5.01 + screenshots.
docs/ — project plan and per-session notes (docs/sessions/).
Makefile — cross-compile, ISO build, QEMU targets.
GPL v2, inherited from memtest86+ (Chris Brady and Samuel Demeulemeester). The PowerPC / Open Firmware port code is GPL v2 to match.