Fix eGPU Driver Errors Code 12 and Code 43 in Device Manager

An external GPU that shows a yellow warning in Device Manager is almost always one of two errors, and they need opposite fixes. eGPU driver errors Code 12 and Code 43 look similar but mean different things: Code 12 is a resource conflict the system cannot resolve on its own, while Code 43 is a fault the driver or hardware has reported. Knowing which one you are looking at saves you hours of guessing.

Quick Answer

Code 12 means the system cannot allocate enough PCIe address space for the eGPU, and the fix is to enable Above 4G Decoding in the BIOS. Code 43 means the driver or hardware flagged a fault, so the fix is usually a clean driver reinstall and checking the connection, with BIOS power-management tweaks if it persists.

Code 12: not enough resources

Code 12 reads as "this device cannot find enough free resources that it can use." With an eGPU, that means the system has run out of PCIe address space to map the card's memory. A graphics card needs a large block of address space, and on many systems the default setting cannot hand out enough.

The fix lives in your BIOS. Reboot, enter the BIOS or UEFI setup, and look for Above 4G Decoding. It hides in different places depending on the board, commonly under Advanced, Peripherals or Boot. Set it to Enabled, save and exit. This lets the system map the card's memory above the 4GB boundary, freeing the address space the eGPU needs. On most machines this clears Code 12 on its own. If your board offers Resizable BAR, enabling it alongside Above 4G Decoding often helps too.

Code 43: the device reported a problem

Code 43 means Windows stopped the device because the driver or the hardware itself reported a fault. It is broader than Code 12 and has a few common causes worth working through in order.

1. Reinstall the graphics driver cleanly. Remove the current driver fully, then install the latest version fresh rather than over the top. A corrupt or mismatched driver is the most frequent trigger.
2. Check the physical link. Reseat the cable at both ends, try a different known-good cable, and make sure the dock or enclosure has solid power. A flaky connection on an eGPU shows up as Code 43 surprisingly often.
3. Look at BIOS power management. If a PCIe power-saving mode is switching off the host port, the card drops out and reports the fault. Disabling aggressive PCIe link power management in the BIOS can stop the port being powered down mid-session.
4. Update the system firmware. An outdated BIOS or chipset driver can mishandle the eGPU connection, so a firmware update sometimes resolves a stubborn Code 43.

If the card works fine in a desktop slot but throws Code 43 only over the eGPU link, the problem is almost always the cable, dock or power rather than the card itself. The eGPU docks and enclosures in the docking stations range at Evetech are where a dodgy connection often gets solved.

Working through both efficiently

Start by reading which code Device Manager actually shows, because the two need different fixes. If it is Code 12, go straight to Above 4G Decoding in the BIOS. If it is Code 43, do the clean driver reinstall first, then check the cable and power, then the BIOS power settings. Change one thing at a time and recheck, so you know which step solved it. If the card itself turns out to be at fault, the best-selling graphics cards at Evetech are a quick way to see current options.

Frequently Asked Questions

What is the difference between Code 12 and Code 43?

Code 12 is a resource conflict where the system cannot allocate enough PCIe address space, fixed by enabling Above 4G Decoding in the BIOS. Code 43 is a fault the driver or hardware reported, usually fixed by a clean driver reinstall and checking the connection.

Where is the Above 4G Decoding setting?

It is in your BIOS or UEFI, typically under the Advanced, Peripherals or Boot section depending on the board. Set it to Enabled, save and exit, and it frees the address space an eGPU needs to clear Code 12.

Why does my eGPU only error over the cable, not in a slot?

That points to the link rather than the card. A faulty cable, an underpowered dock, or a PCIe power-saving mode switching off the port can all cause Code 43 over an eGPU connection while the same card works fine in a desktop slot.

Will reinstalling the driver fix Code 43?

Often, yes. A clean reinstall, removing the old driver fully before installing the latest version, resolves many Code 43 cases. If it returns, check the cable, dock power and BIOS power-management settings next.