PCI-E 8x support?

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Peter

Elite Member
Oct 15, 1999
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Yes. Link width detection and negotiation is a mandatory feature for all PCIE devices.
 
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Algere

Platinum Member
Feb 29, 2004
2,157
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8x PCIe!! News to me and I thought 16x was the de facto standard for PCIe based graphics cards.
 
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Peter

Elite Member
Oct 15, 1999
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Right. But: Some (server grade) chipsets don't have 16x links but do have multiple 8x links. Furthermore, some people want to split the 16x link onto two graphics cards, and give each an 8x link.
 
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otispunkmeyer

Lifer
Jun 14, 2003
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8x also sounds wise for now....seeen as we cant even utilize agp 8 to its full potential, having 2 8x pci-e slots will be better that 1 16x speed one......SLI baby!!!

i know pci-e allows bi- directional data transfer but isnt this not of much use to games? after all data goes to gpu then out the back to your monitor

im having a hard time, that or i jus simply do not know why graphics cards would need to communicate back to the rest of the computer with as much bandwidht as it recieved it
 
nitromullet

nitromullet

Diamond Member
Jan 7, 2004
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I was under the impression that the current (test) SLI systems being run by nVidia are a combination of one 16x PCIe slot and one 8x PCIe slot that was the size of a 16x slot. So, it would appear that the 16x cards will run in a 8x slot provided that the 8x slot is physically enlarged to accept the 16x card. However, I am not aware of any video cards that are to be produced that will run in a normal 8x slot - the card won't fit.
 
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Matthias99

Diamond Member
Oct 7, 2003
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Originally posted by: otispunkmeyer
im having a hard time, that or i jus simply do not know why graphics cards would need to communicate back to the rest of the computer with as much bandwidht as it recieved it
Click to expand...

Video capture (from VIVO cards), as well as video encoding (if NVIDIA ever gets this working on any of the NV4X cards), are two good examples. Encoding HD content in real-time would be too much for the upstream bandwidth of AGP. There are also efforts to be able to use a modern GPU (or at least its programmable shaders) as a sort of co-processor for certain specially coded applications.

So there are ways to use the extra bandwidth that PCIe provides. But, yes, for normal 'render 3D applications on the screen' uses, it's not needed.

Edit: It's also useful if your card needs to buffer textures, etc. in main memory -- but this is pretty slow anyhow, since system RAM is several times slower than video RAM.
 
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Concillian

Diamond Member
May 26, 2004
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A True 8x PCI-e slot is NOT LARGE ENOUGH FOR A VIDEO CARD.

Where people may be confused is that the SLI configurations are talking about using 16 lanes split between 2 16x slots so each get 8 lanes. However, these are still physically 16x slots. If a Dell box says it's an 8x slot, chances are it really is, and a 16x card will not fit.

However, you'll never know without a picture of the PCI-e slot.
 
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Punamo

Senior member
Jan 28, 2001
302
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Ok, so far we have conflicting info about the support. Concillian thinks it's not hardware compatible, but Peter thinks it does. Are there docs that we can refer to?

Thanks a bunch!!!
 
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Peter

Elite Member
Oct 15, 1999
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Originally posted by: Concillian
A True 8x PCI-e slot is NOT LARGE ENOUGH FOR A VIDEO CARD.

Where people may be confused is that the SLI configurations are talking about using 16 lanes split between 2 16x slots so each get 8 lanes. However, these are still physically 16x slots. If a Dell box says it's an 8x slot, chances are it really is, and a 16x card will not fit.

However, you'll never know without a picture of the PCI-e slot.
Click to expand...

On the mechanical side of things, there is no such thing as an 8x slot. Link widths above 4x use the 16x slot's mechanicals.
 
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ChanceT

Junior Member
Nov 30, 2004
2
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GUYS! I need some help please.

I'm building a computer for a client with high requirements.
SATA, PCI-Express video, two 3.0 Xeon CPUs, 1Gb DDR2 memory, etc.

I've already got all the parts but I have a problem with the PCIe.

Here is my motherboard:
Supermicro X6DH8-G2

http://www.supermicro.com/prod...800/E7520/X6DH8-G2.cfm

It has:
3 PCI-X slots
2 PCIe 8x
1 PCIe 4x
No AGP
No integrated video

I know this is a server motherboard but we wanted to use it for a video editing workstation. I ordered a Radeon X600 16x PCI-Express video card that of course doesn't fit in it.

The slots are 8x and not large enough for the 16x vid card.

Q1). Where can I find a really good PCI-Express 8x video card for this motherboard?
Q2). Are their any?
Q3). Am I limited to a crappy PCI card in the PCI-X slot?
Q4). Is their a similar board that that supports the 16x, 800Mh FSB, dual Xeon 3.0, DDRII 400 dual, etc.?

I know I'm asking alot, but I'm in trouble on this one. That board wasn't cheap.

Thanks for any help.

 
biostud

biostud

Lifer
Feb 27, 2003
19,940
7,044
136
Over at tomshardware they put some tape on the lanes of some PCIe graphic cards. they worked fine albeit slower down to PCIe 1x. The only thing is you will still need a PCIe x16 socket for a video card to fit into it.
 
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ChanceT

Junior Member
Nov 30, 2004
2
0
0
Yea, I didn't even notice the onboard video untill after that post. Sorry.

Thats not going to cut it though.

I got to looking at other motherboards from Supermicro, they seem to have a few of them that will support the same memory, cpu, etc and have the 16x PCI Express slot too.

So I guess I'll have to return this board and reorder. All because I didn't no the difference between 8x and 16x. I thought It would be like AGP. You know how an AGP card always fits into any AGP slot 2x, 4x, 8x or whatever. Well I guess I learned the hard way that PCIe dosn't work that way.


Whamp whamp whaaaaaaaa

Back to the drawing board.

Thanks guys
 
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Hikari

Senior member
Jan 8, 2002
530
0
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A x16 board won't work in an x8 slot I don't think. The SLI configurations run at 8x speed-wise, but electrically they are x16. I think you'd have a problem in a 'real' x8 slot.
 
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Cat

Golden Member
Oct 10, 1999
1,059
0
0
People keep saying that since we aren't fully utilizing 8X AGP, 16x PCI-E isn't that big of a deal. This is simply not true. PCI-E has far higher read bandwidth, and PCI-E drivers have a much higher performance potential because you can have asynchronous (no stalling) transfer. Render to texture, occlusion queries, and other graphics techniques should have a healthy speedup.
 
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cbehnken

Golden Member
Aug 23, 2004
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yet, as of now with current cards there have been no benchmarks that show a significant performance increase
 
LTC8K6

LTC8K6

Lifer
Mar 10, 2004
28,520
1,576
126
Yep, there is currently no real difference in performance between 4X AGP, 8X AGP, and PCI-E x16 when displaying video for games, etc.

The PCI-E cards tend to have slightly faster memory, being newer. That accounts for the small speed difference between cards like the AGP 9600XT and the PCI-E X600XT.

Rendering video is where PCI-E should show an advantage. However, there's not much testing to show that yet.
 
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Cat

Golden Member
Oct 10, 1999
1,059
0
0
Current video games don't show a performance increase because they were written with the slow readback of the AGP bus in mind. It's so slow, it's not used often.
 
LTC8K6

LTC8K6

Lifer
Mar 10, 2004
28,520
1,576
126
Cards aren't even using AGP 8X's bandwidth yet.

We were also told PCI-E could deliver enough power to the video cards. Yet they still have to have power cords.

The only benefits of PCI-E are with HDTV rendering and SLI capability. A small segment of the market. In a couple of years maybe we will be using the bandwidth. Just about the time PCI-E V2.0 will come out. :D

There's no point in arguing though, we are going to switch to PCI-E.
 
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