PCIe Extender Cables

Does this picture look familiar? Perhaps you too have a cramped PC chassis? My graphics card is to the left and the metal base of the chassis is to the right. In total I have 8cm (3") of room. Not enough to do any serious hardware work.

My problem is, I often want to debug a PCIe card that’s in that spare slot between the three blue PCI connectors. I don’t have enough room in this chassis to fit everything. The card, my hand as well as one or more probes all need space. What I really want is unfettered access to all the card components, without compromise, while the card is running under Windows or Linux in normal operation. I can’t be effective unless I can inspect card behavior ‘in-flight’. Look at the PCB image here, wouldn’t it be neat if I had that level of access to the board, with decent lighting around it, so you can attach to whatever components you want?

I’d be able to sit comfortably, attach multiple probes, easily see small components from any angle, my job of debugging and diagnosing the hardware would be greatly simplified.

A few years ago I discovered PCIe Extension Cables. PCIe is electrically a serial bus, which means it tolerates a certain amount of physical ‘extension’ to its lanes, unlike traditional PCIe which is a parallel bus and is much more difficult to extend. This PCIe extension capability is useful as it means the PCIe no longer needs to be on the actual motherboard.

Extension cables are cheap. Check Amazon for more details, you should expect to pay $7 or so. On eBay they’re $5 or so.

My cable is 18cm (7") long. On one end of the cable are the PCIe fingers that insert into your motherboard, at the other end is a replica of the PCIe slot on your motherboard. This cable extends the motherboard PCIe slot vertically and creates enough working room either side of the new connector to be useful. This particular cable is a PCIe x1 extension, similar cables exist for PCIe x4 and wider bus connectors.

Once I’ve installed the card and the cable, the card is raised significantly higher and is now fully accessible when the system is running, all I need to do in order to complete the modification is to secure the PCIe bracket to the top of the chassis, so that the card doesn’t move around while I probe it. The card becomes firmly attached to the chassis and can be left like this for days! I used a black zip tie to firmly attach the card bracket to the chassis. It’s solid, the card doesn’t easily move.

I don’t recommend using this technique without securing the card to your chassis as its dangerous. Trust me, no matter how careful you think you’ll be, the card will start to move once you probe it. Do the right thing, buy some zip ties and tie it down.

This brings me to my last picture, the goal of this whole exercise… I can now easily probe the board!

These extension cables are invaluable, I wouldn’t be able to work on PCIe cards and drivers without them. Highly recommended!