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If a desktop will not complete POST or show a display, clearing CMOS can restore default BIOS settings and may help when a problematic setting is preventing startup. You do not need to enter BIOS setup to do it, but you must use the reset method documented for your exact motherboard. A reset is only one troubleshooting step—not a guaranteed fix for every no-POST problem.
What clearing CMOS does—and what it does not do
Clearing CMOS restores BIOS setup defaults, so it can undo an unsuitable configuration even when the computer cannot reach setup. ASUS says stored settings can include the date, time, BIOS password and other setup parameters; Intel describes clearing CMOS as restoring BIOS defaults. See Intel’s explanation of clearing CMOS and the ASUS clear-CMOS instructions.
This procedure does not rewrite or recover BIOS firmware. If the trouble began after a BIOS update, follow the motherboard maker’s firmware recovery instructions instead of assuming a CMOS reset repairs the firmware.
Find the reset method for your motherboard
Identify the exact motherboard model, then consult its official manual or manufacturer support page. Search the manual for terms such as CLR_CMOS, CLRTC or JBAT1, or for a clear-CMOS button. The board determines which method is supported and where its controls are located. ASUS describes a dedicated button, designated pins and battery removal as possible methods, while directing users to check their model’s manual; Intel’s instructions are scoped to systems with Intel boxed desktop processors. Do not guess at pin locations or assume another model’s procedure applies.
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| Method | What to check |
|---|---|
| Clear-CMOS button | Confirm the board has one and follow the manual’s power and press-duration instructions. |
| Designated pins or jumper | Use only the labeled pins specified in the manual; never short unknown contacts. |
| Battery procedure | Check whether the board uses a coin-cell holder or a wired battery, and follow its documented procedure. Do not assume battery removal works identically on every design. |
No one method is universally best: availability, access and the board’s exact instructions decide which is appropriate.
Clear CMOS without entering BIOS setup
- Confirm the board model and instructions. Locate the manufacturer’s manual and the specific clear-CMOS procedure for your board.
- Shut down and isolate power. Turn the system off and disconnect the power cord before opening the case or using a board control. MSI likewise requires complete power disconnection before shorting JBAT1 or removing the battery. Follow your manual’s safety instructions.
- Use only the documented control. Press the clear button, short the specified pins, or use the specified battery procedure exactly as the manual directs. On the ASUS guidance page, the example button or CLRTC pins are held/shorted for about 5–10 seconds; that timing is ASUS’s instruction, not a universal duration for all boards.
- Restore power and start the computer. If a reset notice appears, follow its on-screen prompt. ASUS gives an example of entering setup, loading optimized defaults and saving. If the machine starts, correct the date and time if needed, then review settings before returning to normal use.
Expect custom setup values to be cleared. Review any settings you previously changed, including memory or overclock settings, rather than assuming they were retained.
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If the computer still has no display or will not POST
A CMOS reset cannot resolve every startup failure. Check the basics first, then use the motherboard’s indicators and a minimal configuration to narrow down the cause. MSI and ASUS both recommend systematic checks rather than repeatedly clearing settings.
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Check power and the display path
- Confirm the monitor is powered on and set to the input connected to the computer.
- Reseat the display cable at both ends and verify it is connected to the intended graphics output.
- Check whether the computer shows signs of powering on. A system with no power at all needs power-connection and hardware diagnosis, not just a CMOS reset.
Read the motherboard’s debug indicators
Check the board’s EZ Debug LEDs or other diagnostic indicators, if present, and consult the manual to interpret the indicator that remains lit. The light can help identify which component or startup stage needs attention; do not infer a diagnosis from the indicator name alone.
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Try a minimal POST configuration
Following the motherboard maker’s instructions, disconnect nonessential devices and attempt startup with a minimal set: CPU, cooler, one memory stick, power supply and monitor. If the minimal system starts, reconnect removed devices one at a time to identify what changes the result. ASUS also recommends isolating components and reconnecting them individually when a minimal setup works. See MSI’s no-power/no-display troubleshooting guide and ASUS’s no-power, no-boot and no-display guidance.
If the minimal configuration still does not POST, use the motherboard maker’s support guidance for the exact model rather than repeating the reset indefinitely.
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If the computer boots but you cannot open BIOS setup
This is a different problem from a machine that will not POST. If the computer starts normally but you cannot enter setup, check the motherboard or system maker’s instructions for the correct setup key and when to press it. MSI’s BIOS-entry troubleshooting guide addresses access to setup. Clearing CMOS is not a substitute for identifying the correct key or resolving a keyboard-entry issue.
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