What's the Deal with PCI Express?


What's the Deal with PCI Express?

Ask the Doctor LogoAre x1 PCI Express cards and x16 PCI Express slots compatible? Can I insert my x1 PCI Express soundcard into a x16 PCI Express slot? And maybe this question isn’t relevant, but why do motherboard companies always put their x1 slots between two x16 slots? Even if you install one videocard it will block access to the x1 slot. Of course, you can install your videocard in a secondary x16 PCI Express slot, but how do you know it’s not running at x8 speed? Moreover, if you want to install only one videocard, the motherboard manufacturer instructs you to install it in the topmost x16 slot. But is that required?


Short answer: Yes, a x1 PCI Express card will fit and is fully compatible with a x16 PCI Express slot. Why do most board companies sandwich x1 slots between x16 slots? They do that because if you use a double-width GPU, you only lose access to the x1. If you had a x16 slot next to it, you would lose access to that one. How do you know what speed the slot is running at? Most boards will have the speed printed somewhere on the PCB, but the easiest way is to consult your motherboard manual. We suspect that most motherboard makers recommend that you always install a card in the top x16 slot because those slots are almost always x16. Since the lower x16 slots on many boards actually run at x8 or even x4 data rates, installing in any slot other than the top could be problematic. If you’re curious about what speed your GPU is running at, download the free GPU-Z tool from www.techpowerup.com. In the Bus Interface tab of the utility, you can see what mode your GPU is running under.


SUBMIT YOUR QUESTION Are flames shooting out of the back of your rig? First, grab a fire extinguisher and douse the flames. Once the pyrotechnic display has fizzled, email the doctor at doctor@maximumpc.com for advice on how to solve your technological woes.




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