Running a PCIe 16x card in a PCIe 8x Slot

**Gorganzola** · 10-11-2007, 02:32 PM

Has anyone ever done this? If so what were the results?

*SRTDodge05* · 10-11-2007, 03:04 PM

Think thats the same way SLI works 16x one slot 8x the other. I ran my video card in a 4x pcie and i didnt see any difference.

SpeedDMN · 10-11-2007, 04:23 PM

Quote:

Originally Posted by SRTDodge05

Think thats the same way SLI works 16x one slot 8x the other. I ran my video card in a 4x pcie and i didnt see any difference.

Actually with you average SLi board, both slots share 16 lanes so when you are in SLi mode each card gets 8 apiece. If running a single card, then you use all 16 lanes for the one. The board I have now (Asus A8N32 Deluxe) has 32 lanes so both cards run at the full x16 though I really haven't noticed any improvement in fact I am wondering if SLi even work really at all. GPU-Z seems to think it's disabled...

As to Garganzola's question, I would assume that if they are pin compatible that a x16 card would simply run at x8 for a slight performance hit. I can't think of an example of a x8 PCIe card or slot for that matter 8x AGP sure..

**Gorganzola** · 10-11-2007, 10:49 PM

My biggest concern was doing damage to the equipment. It looks like things are otherwise pin compatible, so I didn't see a reason why it wouldn't work.

Looks like I will have to make the plunge and see what happens, hehe.

SpeedDMN · 10-11-2007, 10:57 PM

Quote:

Originally Posted by Gorganzola

My biggest concern was doing damage to the equipment. It looks like things are otherwise pin compatible, so I didn't see a reason why it wouldn't work.

Looks like I will have to make the plunge and see what happens, hehe.

I'm glad your far enough north from me that the nuclear fallout shouldn't reach this far

ATINUT · 10-11-2007, 10:59 PM

When I ran Crossfire, my first Crossfire board was the ASUS A8R-MVP, and both PCI Express slots were X8 slots, and I ran the videocards just fine.

I wouldn't worry too much.

CK8-04 · 10-11-2007, 11:23 PM

PCIe is very flexible; there is no reason why it shouldn't work. If I can use a 4x RAID controller in a 16x slot, I don't see why putting a 16x card in a 8x slot wouldn't work.

**Gorganzola** · 10-12-2007, 01:23 AM

Let's see here, it either works, or I won't be around to care if it doesn't work. Sold, let's make it happen!

Quote:

Originally Posted by SpeedDMN

I'm glad your far enough north from me that the nuclear fallout shouldn't reach this far

**k0NG0** · 10-12-2007, 05:33 AM

It needs to be a x16 physical slot (i.e. full-length) even if it's only x8 electrical.

That is, half the x16 connector on the card can't just dangle in mid-air. That'll possibly cause floating grounds and all sorts of things (the connector layout isn't "modular" in that sense). I actually looked into this a while back because I seemed to recall PCI-X cards could be plugged into regular PCI slots without a problem, but it turns out PCIe won't do that from what I could find.

**Gorganzola** · 10-12-2007, 12:49 PM

That actually makes sense. Plus, the physical 8x slot is blocked at the end of the connector, so putting the card in that slot would require a Dremel.

I found a decent 1x card that will resolve the issue, the second card is only to add an additional two monitors in the display setup.

The ATI FireMV 2250 PCI Express, will do the job.

Quote:

Originally Posted by k0NG0

It needs to be a x16 physical slot (i.e. full-length) even if it's only x8 electrical.

That is, half the x16 connector on the card can't just dangle in mid-air. That'll possibly cause floating grounds and all sorts of things (the connector layout isn't "modular" in that sense). I actually looked into this a while back because I seemed to recall PCI-X cards could be plugged into regular PCI slots without a problem, but it turns out PCIe won't do that from what I could find.

SpeedDMN · 10-12-2007, 12:58 PM

Yeah which is why I said "as long as they are pin compatible" sounds like they are not. I am not personally familiar with 8x PCIe slots, but it only makes sense that they would be shorter. All my recent boards have 1x,4x,16x no 8x. Again only 8x I am familiar with is AGP. If you have to mod it with a Dremel and leave pins hanging over I would say bad idea.

10-11-2007, 02:32 PM	#1
Gorganzola ABXZone > Facebook Join Date: May 2001 Location: Hangin' with the fruits Posts: 9,383	Running a PCIe 16x card in a PCIe 8x Slot Has anyone ever done this? If so what were the results? __________________ TTFN. I wasn't asleep at the switch, I was drunk. -- Homer J. Simpson Q. How many dull people does it take to change a lightbulb? A. One. A very useful tool on these forums: You can Meebo in public.
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10-11-2007, 03:04 PM	#2
SRTDodge05 Grab Life By The Balls Join Date: Jan 2003 Location: Michigan Posts: 7,830	Re: Running a PCIe 16x card in a PCIe 8x Slot Think thats the same way SLI works 16x one slot 8x the other. I ran my video card in a 4x pcie and i didnt see any difference.
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10-11-2007, 10:49 PM	#4
Gorganzola ABXZone > Facebook Join Date: May 2001 Location: Hangin' with the fruits Posts: 9,383	Re: Running a PCIe 16x card in a PCIe 8x Slot My biggest concern was doing damage to the equipment. It looks like things are otherwise pin compatible, so I didn't see a reason why it wouldn't work. Looks like I will have to make the plunge and see what happens, hehe. __________________ TTFN. I wasn't asleep at the switch, I was drunk. -- Homer J. Simpson Q. How many dull people does it take to change a lightbulb? A. One. A very useful tool on these forums: You can Meebo in public.
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10-11-2007, 10:59 PM	#6
ATINUT Just Plain Crazy! Join Date: Apr 2002 Posts: 3,278	Re: Running a PCIe 16x card in a PCIe 8x Slot When I ran Crossfire, my first Crossfire board was the ASUS A8R-MVP, and both PCI Express slots were X8 slots, and I ran the videocards just fine. I wouldn't worry too much.
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10-11-2007, 11:23 PM	#7
CK8-04 nVidia nForce 4 Join Date: Jan 2003 Location: Malden, MA Posts: 951	Re: Running a PCIe 16x card in a PCIe 8x Slot PCIe is very flexible; there is no reason why it shouldn't work. If I can use a 4x RAID controller in a 16x slot, I don't see why putting a 16x card in a 8x slot wouldn't work. __________________ "To give anything less than your best is to sacrifice the gift" - Steve Prefontaine Antec Solo Corsair 520HX Intel Core 2 Duo E6700 w/ TR SI-128 SE Intel D975XBX2 4GB Corsair DHX DDR2-800 eVGA e-Geforce 8800GT w/ TR T-Rad2 WD Raptor 74GB 16MB NEC Multisync LCD2090UXi Logitech Z-5300 MS Comfort Curve KB 2000 Logitech G3
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10-12-2007, 05:33 AM	#9
k0NG0 Remembering TQ Join Date: Mar 2001 Location: Sweden Posts: 13,623	Re: Running a PCIe 16x card in a PCIe 8x Slot It needs to be a x16 physical slot (i.e. full-length) even if it's only x8 electrical. That is, half the x16 connector on the card can't just dangle in mid-air. That'll possibly cause floating grounds and all sorts of things (the connector layout isn't "modular" in that sense). I actually looked into this a while back because I seemed to recall PCI-X cards could be plugged into regular PCI slots without a problem, but it turns out PCIe won't do that from what I could find. __________________ Use Firefox - "the one that blocks all the schmutz" Feeling multicore elation? Remember this correlation: Amdahl's Law.
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10-12-2007, 12:58 PM	#11
SpeedDMN Silicon Avatar Join Date: Jan 2006 Location: Hyde Park, NY Posts: 2,927	Re: Running a PCIe 16x card in a PCIe 8x Slot Yeah which is why I said "as long as they are pin compatible" sounds like they are not. I am not personally familiar with 8x PCIe slots, but it only makes sense that they would be shorter. All my recent boards have 1x,4x,16x no 8x. Again only 8x I am familiar with is AGP. If you have to mod it with a Dremel and leave pins hanging over I would say bad idea. __________________
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