USB/Sata 3 question

[Dorkenstein]

If I got a motherboard with USB and Sata 3, could I disable it from running in that mode and make it run at 2.0 speeds? Or does it run 3.0 the whole time? I'm kind of hesitant because I heard that the new version can rob a video card of bandwidth, though I'm not sure how big of an issue that is. Thanks.

 

[Blazer7]

I don’t think that this can be done. Since both USB 3 and SATA 6 are backwards compatible there is no real use/need for USB 2/SATA 3 options in the BIOS. In the few boards that I have seen there was only the option to enable/disable the controllers.

As for the bandwidth problem, since the USB 3/SATA 6 controllers are connected to the PCI-E bus it is normal that they will share some bandwidth with the PCI-E slots but AFAIK this happens only when you use these ports. If you don’t, all PCI-E slots should work as advertised and since all current mobos are packed with USB 2/SATA 3 ports leaving those alone shouldn’t be a problem.

There may also be some boards that use dedicated PCI-E lanes for the USB 3/SATA 6 controllers. In that case there will be less PCI-E lanes available for the PCI-E slots but when using the USB 3/SATA 6 ports the PCI-E slots won’t be affected at all.

AFAIK there are no mobos out there that share bandwidth with the 1st PCI-E x16 slot so as far as you don’t CF/SLI you should be fine.

I guess that in the end you’ll have to read the manual of every board you are interested in to learn the specifics.

 

[nipplefish]

AFAIK there are no mobos out there that share bandwidth with the 1st PCI-E x16 slot so as far as you don’t CF/SLI you should be fine.

Actually, many of them will. I originally bought a Gigabyte P55A-UD4P but returned it when I learned this. If you're using SATA3 and USB3 it will take bandwidth from the graphics card lanes, slowing down the first video slot to 8x and preventing use of SLI/CF.

Gigabyte P55A-UD7 and Asus P7P55D-E Pro and above add an additional chip providing extra PCIe bandwidth for the USB and SATA.

If you're going X58 then none of this is an issue, there is plenty of PCIe bandwidth on X58. I don't know about AMD though.

 

[busydude]

Anand did a comprehensive analysis on the performance of 6 Gbps sata on P55/X58 Vs AMD 890GX a week ago. link

 

[Dark Shroud]

You could also just make it easier on yourself and buy a mobo without USB3 & SATA3 and plug this in: http://www.newegg.com/Product/Produc...82E16813995004