mobo recommendations and pci-e questions

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pRS317

Limp Gawd
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Jun 23, 2005
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i have an LSI MegaRAID SCSI 320-2E on order and i'm wondering which motherboard will be best to use it in. it supports an x8 pci-e slot and i'm wondering if i could use it in one of the x16 slots on an sli board, or are they specifically reserved for video. i've also seen some boards with x4 slots, are the sizes any different based on the x values?

here's a link to the host adapter i'm getting, if that helps:
http://www.lsilogic.com/products/megaraid/megaraid_320_2e.html

thanks!
 
Well, the thing about pci express is, there's physical size and logical size. Some boards (okay, a lot) have the single nforce4 chipset, giving them 20 lanes of pci express, so they split 8/8/4 or 16/2/2 depending on your sli settings. However, the physical size of the slots isn't going to change by a bios setting, right? So they build in 2 x16 sized slots and 1 x4 sized slot, even though you could never use all of those lanes - the chipset would need 36 lanes. Cards have to deal with this, too; you don't want to have problems with a card in x8 mode and have it work in x16 or vice versa.

So manufacturers of motherboards looked at this and realized that the only thing holding addon cards in place would be a screw and the connector. In many instances, they made the slot physically larger than would be used, so that one could fit cards designed for more lanes into them. The LSI card is x8, so you may be able to find a motherboard that has an x4 logical/x8 physical slot and use it in that, or get a standard 2-slot x8/x8 in x16 form factor board and use it there. There shouldn't be any problems using it in the second slot on an SLI board.

I hope I answered the question :p

 
With the Areca I had heard of someone having a problem putting it into a SLI slot and it ended up running at 1x for some reason, not sure if that was really the problem or what but I ended up just getting the a8n32 for my system and I don't have a single worry in the world (btw the areca has a physical size of an 8x slot)
 
the second sli slot running at x1 would explain this explanation of the slots which was confusing when i first looked at it:

"PCI Express x16: 2 x PCI Express X 16 (*SLI mode : x8 , x8 *Default Single VGA mode : x16, x1)

the a8n32 is a bit pricy from what i'm seeing, so i guess a bord with an x4 slot is the next best thing?
 
Here's something worth mentioning: compare this picture with this one. See how in the first one, you can see the board between the end of the pci-e x4 slot? This is both a logical and physical x4 connector, but it's had the end knocked out so that you can install longer cards. The card will autodetect how many lanes it has available, and only use the 4 that exist. So I'd tend to get something with the endless connector rather than a closed one. You can cut the end out (the famous example is Dells with an x8 slot which everyone figured out could be chopped up so one could use x16 video cards) but that's sort of a messy solution.

I think "sli mode" isn't limited to SLI setups - even with one video card and one raid controller, you could still run the slots at x8/x8.

 
okay, as i'm figuring this out, the controller is physically unable to be placed into a x1 slot, correct? i had the idea of using an asrock mobo that supports agp and x16, since i'm still using an agp card. does that sound like a workable solution?

i was almost thinking about going with a x1 board as the bandwidth is quite higher than will be filled by my raid, but obviously the physical dimensions are a bit prohibitive.

ps, thanks for all the well thought out thoughts!
 
I think that'd work, but I'd stick with the tried-and-true nforce4 myself. It's gotta be the replacement for the 440bx - everything had that :p Maybe a board with onboard video? Just make sure it's got an open-ended pci-e slot or an x16 sized connector.

 
well, i posted the question as to whether it would work in the mobo section, and got a confirmation. "It's just a regular x16 pci-e slot which can be used for any pci-e device whatsoever, be it 1x all the way up to 16x. And the agp slot on those boards is actually a real, pure agp slot so no issues there."

i found the board in the newegg refurb section for $40.60 shipped, so if it doesn't work out, i should be able to resell it for about the same price.

thanks again for the schooling!
 
If you are making a NAS or something like that, where you don't use the computer for anything but storage, just get a single pcie 16x slot board and put the raid in the 16x slot and get a pci video card.
 
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