# PCIe x16 : x4 mode ?



## bonanza (May 11, 2007)

There are some mobo that provides 2 PCIe x16 (for SLI or Crossfire).  However many of mainstream mobo, the secondary PCIe x16 doesn't work at full speed in SLI/Crossfire mode.

For example this asus P5B deluxe :
2 x PCI-E x16 (blue @  x16 mode, black @ x2 or x4 mode)

The question is :
Can I utilize a RAID x8 card at the secondary PCIe x16 (black) ? (I mean the RAID card is not vga card so I hope the second PCIe x16 provides at least x8 speed, due this is not SLI mode).

Many thanks.


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## StrangleHold (May 11, 2007)

If your looking at a motherboard for a intel processor the Nvidia Nforce 590 and 680 chip runs both PCIe X16 in X16 mode in SLI, if you can find one intel Nvidia Nforce 4 SLI X16 does too


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## bonanza (May 12, 2007)

No.  I just want to run RAID x8 card on the secondary PCIe x16.

2 x PCI-E x16 (blue @ x16 mode, black @ x2 or x4 mode)
Please notice the "black @ x2 or x4 mode".  It makes me doubt if I can run x8 *RAID* card.


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## The_Other_One (May 12, 2007)

I wouldn't worry too much about it.  There was a benchmark on a motherboard I read a while back that had both an AGP and PCI Express slot for video.  However, due to chipset limitations and all, the PCI Express slot was limited to I beleive 4x.  You'd think this would have a major impact on graphics performance, but actually, the card was only slightly slower than a similar PC with a standard 16x slot.


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## junwang0808 (May 12, 2007)

hmmm i use an AGP card on my OLD PCI slot for graphic card. even high end graphic card runs terriably slow..   and some software shows they run at 4x some shows at 8x but who knows...


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