PCI-e 2.1 Card in a PCI-e 1.1 Motherboard

This is something that well and truly has me stumped. The situation is that my brother's computer is lacking a bit of graphics grunt and could do with something a little better than integrated graphics. My brother only does light gaming, but he is after playing StarCraft II which is why his computer now needs a bit more GPU muscle.

Anyway, I thought I'd found the perfect card for his needs. The Radeon HD 5570 seems to be a worthwhile option for the computer while keeping within the limitations of the PSU. The PSU is 300W with 19A on the +12V rail. Sounded like it would be fine for the job. But then I heard that since it uses PCI-e 2.1, it might cause problems on older motherboards which support 1.x. The chipset this computer uses in particular is G33 which supports PCI-e 1.1. The computer itself is a Compaq DX2400. The thing that has led me to post this thread is that some people say it works fine, while others say it won't.

I'd appreciate it if this can be clarified so I don't end up spending money on something that ultimately won't work. I'm finding it a bit embarrassing that I should probably know better, yet this is turning out to be such a nightmare, and it's driving me crazy! :pt1cable:
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  1. Plenty of issues with the version 2.1 cards but not with the 2.0 cards. There are more options for version 2.0 in HD5670 cards http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007709%20600007320%20600007609%20600007855&IsNodeId=1&name=PCI%20Express%202.0%20x16
    They will run on his PSU just fine, here is a power bench where total system pulls only 190watts under load http://www.anandtech.com/show/2917/13
  2. Ah, I didn't know there were PCI-e 2.0 versions of the Radeon HD 5000 series cards. I thought they were all 2.1.

    Also I see that the benchmark you linked to was done on a Core i7 920, so that makes the power load even more impressive. :)

    I think I'll go with the Sapphire HD 5670 1 GB GDDR5 so he can enjoy SC2 in decent enough settings. I'll keep you updated when it arrives. Thanks!
  3. Buy the cheaper HD 5670 512MB version since there is no performance difference.

    See following benchmarks which compares both versions of the HD 5670 and an overclocked HD 5670:

  4. Fair enough. I just ordered the 512 MB version. Thanks again! :)
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