I have old HP PC. Model: HP Compaq dc5700 Microtower


It has PCI Express x1 slot. I would like put in this slot Graphic card with PCI Express 2.0.

For example this model: http://www.agem.sk/produkt/sapphire-radeon-hd-5450-512mb-16660478.html

I am not sure if it will work.

  • I've heard a few reports of people using non-1x devices on 1x slots. I know from experience that 1x devices work in 4x (and higher slots), but I have not personally tried running a 4x (or higher) device in a 1x slot. – Breakthrough Feb 29 '12 at 14:05
  • For PCIe devices, the "x" refers to the number of communication lanes, and determines the physical size of the slot. That's why we say "x1" instead of "1x", which would imply only a difference in speed. Because of this, an x4 card would not physically fit in an x1 slot. – rob Feb 29 '12 at 17:40

You're comparing apples and oranges here, kinda.

Version Vs. Size

  • "x1" refers to the SIZE of the port on the mainboard.
  • "2.0" refers to the VERSION of PCI Express the card uses to communicate. Based on the age of your system, your computer probably communicates using version 1.0 of PCI Express.

Backwards Compatibility

PCI Express is backwards compatible, which means:

  • A PCI Express 1.0 card can connect to a PCI Express 2.0 mainboard. It is the board that is backward compatible, not the card.
  • If you try to connect a PCI Express 2.0 card to a PCI Express 1.0 slot it may or may not work.
  • Backwards compatibility always applies to the mainboard (the host) and not the peripheral.

What it all means in your case

Your system is most likely too old to support PCI Express 2.0. Looking at both the version AND the size, you have the following specs in your computer and in the desired hardware:

  • Computer: PCI Express version 1.0, slot size x1.
  • Video Card: PCI Express version 2.0, slot size x4 (or x8)

This is a version problem (the card is a newer version than the mainboard) and a size problem (the card connector is larger than the mainboard slot). While the size may or may not be an issue, as others have noted here, the version probably will.

So while there may be a slight possibility the card will work in the computer, it is much, much more likely it will not work at all.


PCI-E 2.0 is designed to be fully backward compatible in most cases, unless you're unlucky. You may experience degredation in performance due to the reduced IO bandwidth available to the card through the PCI-E slot, but in reality you shouldn't notice it.

I think this should help answer your question.

Just to qualify this statement, I'm currently running Battlefield 3 on High settings on the following hardware: Gfx card; Motherboard

  • This isn't backwards compatibility, which always applies to the mainboard. This is forwards compatibility, which isn't supported. – music2myear Feb 29 '12 at 14:40

I have tried various adapters in the past and they work nicely, however bandwidth is limited. The last time I used the adaptors (for example any of these) it was to build a GPGPU computer (and it worked fine): my motherboard has 3 PCIe full size slots and 1 PCIe x1 slot, using an adaptor I can use 4 GPUs for GPGPU purposes, and have seen bitcoin mining machines with as many as 8 GPUs using the adaptors.

You can also utilise the ASUS 4way sli bridge to increase the number of GPUs you can use... Although not by as much as this: enter image description here :)

  • Apologies for the picture, it was the only one I could find from the article. – GMasucci Apr 4 '14 at 15:28

PCI Express v1.0 slots are usually compatible with v2.0 cards, but usually not v2.1 cards in 1.0 slots as the power requirement of the slot changed, killing much of the backwards compatibility. I have tried a few 2.1 cards in v1.0 boards and can confirm the ones I used don't work.

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