BIOS/UEFI Error Beeps & POST Codes: RAM/CPU/GPU Diagnosis

Use this guide to interpret early-boot failures safely and decide whether the issue is boot order/config, disk detection, or hardware health signals.

More systems guides Systems & Devices hub BIOS / UEFI hub

TL;DR

✓ Beep/POST patterns vary by OEM; identify the vendor first.
✓ Start with power/cables/drive detection basics.
✓ Bootloader messages often indicate boot config or drive issues.
✓ Avoid unsafe hardware handling; follow OEM procedures.

Quick Navigation

Symptoms Root Causes Step-by-step fixes What NOT to do If it persists Code directory Related guides & hubs FAQ References

Symptoms / When you see this

✓ PC powers on but won’t boot OS.
✓ Messages like “no bootable device”, “bootmgr is missing”.
✓ PXE/network boot messages appear unexpectedly.
✓ Beep patterns or POST indicators appear (vendor-specific).

Root causes (grouped)

✓ Boot order and boot mode mismatch.
✓ Drive not detected or unreadable.
✓ Bootloader/partition issues after cloning or partition edits.
✓ Hardware health warnings depending on model.

Step-by-step fixes (safe, prioritized)

✓ Remove external boot media and check boot order.
✓ Confirm system drive is detected in BIOS/UEFI.
✓ Reseat cables on desktops (power off) if applicable.
✓ Prioritize data recovery if disk read errors appear.
✓ Use official recovery media for boot repair.

What NOT to do

✓ Do not flash firmware without stable power and correct image.
✓ Do not change partitions without backups.
✓ Do not continue repeated boot attempts on a failing drive without a recovery plan.

If it persists (escalation checklist)

✓ Record exact message/beep pattern and hardware model.
✓ Use OEM documentation for your board/laptop.
✓ Seek professional service when hardware faults are suspected.

Code directory within this guide

✓ Beep codes vary; this directory focuses on widely shown messages and safe interpretation paths.

Code	Meaning	Next step
A DISK READ ERROR OCCURRED	Disk read failure — The system failed to read from the boot disk during early boot.	Follow the checklist on the code page
BOOT FAILURE	Insert system disk — Firmware could not boot from the current device and is prompting for bootable media.	Follow the checklist on the code page
BOOTMGR IS MISSING	Boot loader missing — The system cannot find the Windows Boot Manager on the selected boot device.	Verify the correct path/resource and prerequisites
DISK BOOT FAILURE	Boot device not bootable — The selected disk does not contain a valid boot record for the current boot mode.	Follow the checklist on the code page
INVALID PARTITION TABLE	Boot partition issue — The system found an invalid or non-bootable partition table on the selected drive.	Follow the checklist on the code page
NTLDR IS MISSING	Legacy boot loader missing — The system is attempting a legacy boot but cannot find the required loader on the boot device.	Verify the correct path/resource and prerequisites
OPERATING SYSTEM NOT FOUND	No OS detected — Firmware could not find a bootable operating system on the selected device.	Verify the correct path/resource and prerequisites
PRESS ANY KEY TO BOOT	Booting from external media — The system detected bootable external media and is asking whether to boot from it.	Follow the checklist on the code page
PXE BOOT FAILED	Network boot fallback — The system attempted to boot from the network (PXE) and failed, often after it couldn’t boot from local storage.	Follow the checklist on the code page
REBOOT AND SELECT PROPER BOOT DEVICE	Wrong boot device — Firmware cannot find a bootable device from the current boot order selection.	Follow the checklist on the code page
BOOT DEVICE NOT FOUND	Boot device unavailable — Firmware could not locate the configured boot device or boot partition.	Verify the correct path/resource and prerequisites
CMOS BATTERY FAILURE	RTC/CMOS battery issue — Firmware reported that the battery maintaining time/settings is not functioning correctly.	Follow the checklist on the code page
CMOS CHECKSUM BAD	Firmware settings invalid — Firmware reported that stored configuration data failed validation.	Follow the checklist on the code page
CPU FAN ERROR	Cooling issue detected — Firmware detected a problem with CPU cooling fan operation.	Follow the checklist on the code page
KEYBOARD ERROR OR NO KEYBOARD PRESENT	Input device not detected — Firmware reported that a required keyboard input device was not detected during POST.	Follow the checklist on the code page
NO BOOTABLE DEVICE	Boot device missing — Firmware could not find a valid bootable device for the configured boot order.	Verify the correct path/resource and prerequisites
PXE-E61: MEDIA TEST FAILURE	Network boot attempted — The system attempted network boot because a local boot device was not found.	Verify the correct path/resource and prerequisites
SECURE BOOT VIOLATION	Boot blocked by policy — Firmware blocked boot because Secure Boot validation failed.	Follow the checklist on the code page
SMART STATUS BAD	Drive health warning — Firmware reported a storage device health warning condition.	Follow the checklist on the code page
TPM DEVICE NOT DETECTED	TPM unavailable — Firmware could not detect or initialize the TPM required for security features.	Follow the checklist on the code page

Tip: If your exact code isn’t listed, use the closest hub link above and browse related prefixes or message patterns.

FAQ

Are beep codes universal?

No. They vary by BIOS vendor and OEM. Identify the exact vendor/model first.

Why do I see PXE boot messages?

Often because the system didn’t find a bootable local device and moved to network boot.

Does BOOTMGR missing mean Windows is unrecoverable?

Not necessarily. It often indicates missing boot files or wrong boot device selection.

Safest first check?

Confirm the OS drive is detected and first in boot order.

When should I stop and back up?

When disk read errors or health warnings appear.

Is firmware update a fix?

Sometimes, but it carries risk. Only do it when OEM recommends and power is stable.

Can a loose cable cause boot failure?

Yes, especially on desktops.

What should I capture for support?

Exact message text, hardware model, and recent changes (drive swap, BIOS reset).

References / Notes

✓ OEM BIOS/UEFI documentation
✓ Drive health diagnostics
✓ Official recovery media guidance