PCI-E Question for D975XBX2 Owners

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AARRGGHHH
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PCI-E Question for D975XBX2 Owners

Postby AARRGGHHH » Thu Jun 14, 2007 2:59 am

I'm confused on the 16x / 8x / 4x PCI-E connectors on this Intel board. I downloaded the PDF manual, but I'm still not sure I'm understanding correctly.

I'll use this as an example: I use a graphics card in the PCI-E 16x slot. Lets say I add two more cards (this may well happen): a PCI-E eSATA Multiplier Card in the PCI-E 8X slot, and an external Firewire 800 card in the PCI-E 4x slot.

If I were to do that, would the graphics card in the first slot automatically drop to 8x? Or is there a way I keep it running at 16x, while my other slots run at 8x and 4x?

I think it's this Crossfire thing that has me confused, because when using Crossfire, the connectors seem to switch to 8x 8x 4x speeds, for Crossfire support. But if you're not using Crossfire, are you still forced into 8x 8x 4x if you use all three connectors?

Another scenario I can picture is my main nVidia graphics card in the 16x slot, an older nVidia graphics card in the 8x (more for adding extra monitors than adding extra GPU power), and a Firewire 800 or eSATA multiplier in the 4x slot. Because there's two video cards here, I have the same question, am I forced into 8x 8x 4x, or can I still operate at 16x 8x 4x ?

I know that was a bit confusing, and I'm very appreciative of any help.

Thank you

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Re: PCI-E Question for D975XBX2 Owners

Postby mickrussom » Thu Jun 14, 2007 10:21 am

If you put more than one card in the first two slots, they drop to x8. You can see the PEG-lane count in the BIOS (you can answer this question by putting cards in and checking the BIOS for what the PEG lane count is).

If you have a video card in the primary slot, and put *anything* in the second slot, even a 1x, the two slots become x8+x8.

so the configuration options are :

16x 0x 4x
8x 8x 4x

This is what I have determined through experimentation.

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Re: PCI-E Question for D975XBX2 Owners

Postby mickrussom » Thu Jun 14, 2007 10:26 am

AARRGGHHH wrote:
I know that was a bit confusing, and I'm very appreciative of any help.

Thank you


Another way to look at this is here:

http://www.intel.com/products/chipsets/975x/index.htm

Tee 975X has 16 lanes. The ICH7R has 4. There is no way to exceed 20 lanes on this board.

Assume for a moment the 4x slot over in the corner is always on the ICH7R. The 975X must give its 16 lanes to the other two slots.

Since express can be 1x, 4x, 8x or 16x, if any lane is required on the second slot the first one must drop to x8.

The 975X chipset is showing its age here with a small total lane capability.

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Postby AARRGGHHH » Thu Jun 14, 2007 5:20 pm

Thanks very much for the replies.

mickrussom wrote:The 975X must give its 16 lanes to the other two slots.


Is there any way to change the lane assignments in the BIOS (or anywhere else)? In other words, of the 16 available 975X PCI-E lanes, can I allow 12 for the graphics card, and 4 for a secondary card?

mickrussom wrote:The 975X chipset is showing its age here with a small total lane capability.


I havent bought the board yet. Are there other 975X boards with more lanes, or would I have to go with an SLI board for additional lanes?

I appreciate the help.

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Postby mickrussom » Fri Jun 15, 2007 12:09 am

AARRGGHHH wrote:Is there any way to change the lane assignments in the BIOS (or anywhere else)? In other words, of the 16 available 975X PCI-E lanes, can I allow 12 for the graphics card, and 4 for a secondary card?

I havent bought the board yet. Are there other 975X boards with more lanes, or would I have to go with an SLI board for additional lanes?


Here is why I think its not possible. I believe PCI-express is specified as 1x, 4x, 8x and 16x. While other lane counts to devices may be possible (like any number between 1 and 16 that isnt 1,4,8,16), I haven't seen it.

My experience with this board is no, it falls from 16x to 8x if anything touches the second PCI-express slot. My idea of how this works is this: If 16, 8, 4, 1 are the only valid modes, than any needs for any lanes off of the 975X in the second slot would cause the 16 lanes to go to 8, since that is the next valid lane-amount.

You might think, hey, ill but a 1 lane card in slot 2 and the PEG (slot 1) will run in 15x - not the case, i tried this, it drops to 8.

I would wait to see the Bearlake x38 boards coming out shortly if you haven't bought.

For a sample of what is to come:
http://www.hexus.net/content/item.php?item=8923
See the Gigabyte GA-X38-DQ6 (DDR2) or GA-X38T-DQ6 (DDR3).

They have dual PCI-express x16 * x16 electrical, meaning 32 lanes dedicated to those two slots.

I don't believe this would ever be possible in the 975X family.

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Postby AARRGGHHH » Fri Jun 15, 2007 3:37 am

I suppose I should, in fact I will, at least consider an SLI board, since they apparently have 2 or 3 16x slots.

However, I'd still prefer to go Intel

Thanks very much for your replies

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Postby mickrussom » Sat Jun 16, 2007 2:50 am

AARRGGHHH wrote:However, I'd still prefer to go Intel Thanks very much for your replies


I share this sentiment, despite my frustration about the XBX2. I've never been a fan of SiS, Via or the "other" categories. I've done ok with ServerWorks, Intel, and Pure AMD (AMD-8111/8131), but those "other" guys, like Nvidia, ATI, SiS, VIA, never floated my boat.

Check out specs on:
http://en.wikipedia.org/wiki/List_of_Intel_chipsets

The Bearlake X38 will have two x16 PCI-express 2.0 ports. It might be worth the wait for a month or two.

I personally will not buy Nvidia or ATI chipsets due to problems I've had with them through the years. I can usually fix, resolve get them working, thats not the problem, its the amount or severity or annoyance-level of the issues that gets me the most.

Intel is clearly taking a bad turn with regards to support issues, but behind the ass-support, they are the makes of the world's best silicon right now (and Im not talking about the Itanic/Itanium piece of crap), and they can certainly handle the chipset.

I think they should consider licensing BIOS code if they cant make a decent BIOS themselves.

Anyways, I feel the pain, you want to go with old faithful - but right now, you are right between the 975X and something else.

I plan to dump the XBX2 for a Bearlake X38 as soon as its feasible.

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Postby vbironchef » Sat Jun 16, 2007 11:23 am

same here. Thinking about going under water too.

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Re: PCI-E Question for D975XBX2 Owners

Postby AARRGGHHH » Fri Jun 29, 2007 5:27 am

Sorry about the delayed reply, I've had an insane work schedule.

mickrussom wrote:Check out specs on:
http://en.wikipedia.org/wiki/List_of_Intel_chipsets

The Bearlake X38 will have two x16 PCI-express 2.0 ports. It might be worth the wait for a month or two.


That's interesting, thank you. I didnt know that any of the new Intel chipsets had 2 PCIe x16 slots.

I was thinking about using that second slot for something like an eSATA card, but I'm curious about whether there's an option to use 2 nVidia graphics cards. The Intel site says very little: "The Intel® G35 Express Chipset and the advanced Intel® X38 enthusiast chipset with dual graphics support will ship within 90 days." So it says "Dual Graphics Support", but it doesnt say if it's limited to ATI cards, or if it includes nVidia. In any case, two x16 ports would be nice. :-)

Since the prices will drop soon, I could probably put a Q6600 Core 2 Quad 2.4 Ghz in here, correct? I guess that depends on whether they release a BIOS for "older" chips like the Q6600.

My main concern here will be that this is a first generation board. How long does it usually take for the first revision to come out?

As always, many thanks.

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Re: PCI-E Question for D975XBX2 Owners

Postby hurf_durf » Wed Mar 12, 2008 1:02 pm

Will a PCI Express 2.0 graphics card work on this board?

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Re: PCI-E Question for D975XBX2 Owners

Postby DaddyRabbit » Sat Mar 22, 2008 6:47 am

hurf_durf wrote:Will a PCI Express 2.0 graphics card work on this board?


Yes, PCI-E 2.0 is backward compatible
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Re: PCI-E Question for D975XBX2 Owners

Postby boomer_1005 » Wed Aug 08, 2012 10:12 pm

DaddyRabbit wrote:
hurf_durf wrote:Will a PCI Express 2.0 graphics card work on this board?


Yes, PCI-E 2.0 is backward compatible


so will gen 3.0 pciexpress will also work with this motherboard???

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Re: PCI-E Question for D975XBX2 Owners

Postby Sparky » Thu Aug 09, 2012 5:21 am

Yes, it's backwards compatible.
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