PCI Express Downstream Switch Fix – PCI-e Port Won't Detect

By Published June 06, 2015 at 8:30 am

Over the course of our recent GTX 980 Ti review, we encountered a curious issue with our primary PCI Express port. When connecting graphics cards to the first PCI-e slot, the card wouldn't detect and resolution would be stunted to lower values. Using one of the other slots bypassed this issue, but was unacceptable for multi-GPU configurations – something we eventually tested.

The Problem

We encountered a yellow bang in device manager (devmgmt.msc) for “PCI Express Standard Downstream Switch Port,” and the failing device corresponded with our first PCI-e slot. This issue arose after performing a driver cleansing; we used a driver cleaning tool to remove all AMD and nVidia drivers prior to benchmarking and, this time, the blast blew away our PCI-e downstream switch port. It may be the case that this is an issue relegated to boards with PLX multiplexing for PCI-e lanes, as our board does utilize a PEX chip to optimize lane switching.

Attempted Solutions & The Fix

We tried a few things to fix this. The first, obvious step was to reinstall all the core motherboard drivers related to PCI-e and the PCH / chipset. We started by reinstalling the Intel chipset drivers, but didn't experience any luck in recovering PCI-e functionality. Attempts to remove and re-install all video drivers in safe mode were also ineffective at fixing the first PCI-e port, though did allow us to connect the card to other slots.

A bit later, we disabled the PCI-e downstream switch port in devmgmt.msc, restarted, and reinstalled the chipset drivers again. Still no luck.

At this point, options were running out. I decided to uninstall the failed device from device manager (right click – uninstall) and reboot, then reinstall the chipset drivers again. At this time, I also went through the Windows update utility to download missing drivers and Windows updates.


The above steps resolved our missing PCI-e downstream switch port problem and got the slot functioning again. If you're having similar problems, give the above a shot and comment below.

- Steve "Lelldorianx" Burke.

Last modified on June 05, 2015 at 8:30 am
Steve Burke

Steve started GamersNexus back when it was just a cool name, and now it's grown into an expansive website with an overwhelming amount of features. He recalls his first difficult decision with GN's direction: "I didn't know whether or not I wanted 'Gamers' to have a possessive apostrophe -- I mean, grammatically it should, but I didn't like it in the name. It was ugly. I also had people who were typing apostrophes into the address bar - sigh. It made sense to just leave it as 'Gamers.'"

First world problems, Steve. First world problems.

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