Motherboard · high

How to fixPOST-CODE-99

POST Code 99 - Super I/O Initialization

What this error means

POST Code 99 - Super I/O Initialization ranks as a high-severity motherboard issue in our database. Motherboard debug code 99 indicates a failure during Super I/O chip initialization, which handles legacy hardware connections, front panel ports, and display outputs. Most commonly caused by loose display cables, graphics card seating issues, or conflicting USB devices. This can also stem from corrupt BIOS settings or outdated firmware. Use the steps below to track down and fix the cause.

Before you begin

Save open work and back up important files. Note any recent driver or hardware changes. If Windows cannot start, use the startup guide first.

Work through these checks

0 of 4 complete
01Ensure display cable is plugged into the discrete GPU, not motherboard

Ensure display cable is plugged into the discrete GPU, not motherboard.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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02Reseat the graphics card in the primary PCIe x16 slot

Reseat the graphics card in the primary PCIe x16 slot.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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03Unplug all non-essential USB devices and restart

Unplug all non-essential USB devices and restart.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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04Perform a CMOS reset to clear hardware mapping

Perform a CMOS reset to clear hardware mapping.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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Possible causes

  • Incorrect display output connection or cable
  • Graphics card not fully seated in the PCIe slot
  • Conflicting external USB or SATA storage devices
  • Corrupt BIOS settings or outdated firmware