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Bottlenecking on pcie x16 (x16 signal vs x4?)

Last response: in Graphics & Displays
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July 25, 2008 5:40:47 AM

So I'm in a rather unusual situation I believe. Finally upgrading my x1900xt to either a GTX 260 or HD 4870. However, both of these cards are huge, which is causing issues in my case. First, they both cover up the chipset fan and sata ports and second, they bump up against the hard drive rack. This can be partially solved by putting them into the second (lower) pcie slot, however this is where I am confused. Only relevent hardware is the board, a Tyan S2877 Tiger, in case you want to look up more detail. (Other info should anyone see it needed: Dual Opteron 275s, Antec P180 case, 4gb, Vista-64, Antec Truepower Trio 550w.)

Basically, these 2 slots are definded as PCIe x16 (1.x spec I'm almost sure of) but one is labeled as x16 signals and one as x4. What is the difference? I have a bad feeling that I will be bottlenecked by this should I put a new card in that second slot rather than the first. I ran a 3dMark06 with my x1900xt in both slots and got essentially the same result, but I don't know if this card can really push the limit of the slot. My monitor is at 1680x1050 so not the most demanding out there and I don't anticipate changing that anytime soon.

If anyone can clarify what the difference in my pcie slots is and if it could cause bottlenecking should I put something like a 260/4870 in that second slot, I would greatly appreciate it. Trying to order this thing soon and this is hopefully the last hurdle I'll have to deal with. Thanks.
July 25, 2008 7:41:29 AM

Solution is to throw your pc out the window and build a new one . your post makes no sense at all .
a c 169 U Graphics card
July 25, 2008 7:47:23 AM

http://www.tomshardware.co.uk/forum/245454-15-crossfire...

A note about Motherboards:

Some Motherboards support Multi-GPU Technology at Dual 16x mode, some support it at Dual 8x mode and some support it at 16x 4x mode, what are the differences?
Well for getting the best performance out of Multi-GPU cards,you need a Motherboard that supports Multi-GPU at dual(Or more) 16x mode like Nvidia 790i ULTRA SLI, Nvidia790i SLI, Nvidia 780i SLI, Nvidia 680i( As i said, NVIDIA 790i ULTRA SLI ,790i SLI ,780i SLI and 680i SLI support 3-Way SLI too),Nvidia 590i SLI, Nvidia nForce4 SLI 16x, ATI CrossFire Xpress 3200 or Intel X38 chipsets.

Dual 8x is a very good configuration too,it doesnt have alot of difference with Dual 16x and its cheaper too.
Chipests like Nvidia 750i SLI, Nvidia 650i SLI,NVIDIA 570i SLI, NVIDIA nForce4 SLI, ATI Radeon Xpress 200, Intel 975x and ONLY 2 Intel P35 boards(ASUS BLITZ FORMULA and ASUS BLITZ EXTREME) support Multi-GPU at dual 8x mode.

However,there are some expections too,for example EVGA has a 750i Motherboard(The model of it is
EVGA 750i SLI FTW)Which supports SLI at dual 16x mode unlike many 750i Motherboards which support SLI at dual 8x mode.

The last one is 16x 4x, this one is the weakest and doesn't perform very good compared to dual 8x or dual 16x,so i won't recommend it for Multi-GPU configuration. Intel P35 and P965 chipsets support Multi-GPU at 16x 4x mode.

Here are some benchmarks that help you understand it better:
Dual 16x vs Dual 8x (ASUS A8N32-SLI DELUXE vs ASUS A8N-SLI PREMIUM) Its an old but good article:
http://www.xbitlabs.com/articles/mainboards/display/asu...

Dual 8x vs 16x 4x (ASUS P5B DELUXE vs P5W-DH DELUXE)
http://www.anandtech.com/video/showdoc.aspx?i=2837

Nvidia 680i (Dual 16x) vs Nvidia 650i SLI(Dual 8x)
http://www.techspot.com/review/45-nvidia-nforce-650i-sl...

Related resources
July 25, 2008 8:52:59 AM

The PCIe x4 slot has only a quarter of the bandwidth the x16 slot has. Depending on the graphics card that can be a sever bottleneck or barely noticeable. PCIe x4 roughly corresponds to AGP.

I would advise against putting a high performance card in a x4 slot.
July 25, 2008 9:21:43 AM

Don't listen to Slash, your board is fine. If you put a 4870 or a gtx 260 in that lower slot you will see significant performance loss. You will be fine in the x16 slot, as tests have shown no measurable loss of performance in the 1.1 slots. If you're are having trouble fitting it then I would suggest perhaps moving your hard drive to another rack of your case if it supports it, and if you can reach it with your cables. Rearrange as needed... it would be a shame not to get one of these cards because it can't fit in your case. Worse comes to worse you can always get a new case. Cooler master has a great one that supposedly can fit 2 8800 gt's in sli.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

(It can also support up to 7 120 mm fans)

Good luck making everything to work ;) 
July 25, 2008 2:45:35 PM

Thanks for the later responses clears it up a little bit for me. I purchased/returned a gtx 260 from BB just to get an idea on how it fits. Hard drives aren't the issue the cage can be removed. The main problem I am having is that when the card is installed, that casing on it completely covers the chipset fan and is only separated by a couple mm of space. The fan is a piece of junk so I'm pretty sure covering it wouldn't turn out well. (I want to blame Tyan for this horrible design...but it is a server board, they probably didn't consider much for gaming)

Here's a picture of what I'm dealing with, big white thing in the top is the current x1900xt fan casing, a gtx 260 will be the same height...but across the whole image.
hopefully that linked correctly

Anyways, thanks again for the help. Looks like I'm either going to try it out and rely on Newegg's return policy should it block too much airflow or look harder at the 4850's.
July 25, 2008 4:58:12 PM

You might get away with mounting a passive cooler and a 80 or 120 mm fan. If you take a good quality one with decent cooling paste it might even improve temps.
July 25, 2008 6:39:26 PM

This is an excellent passive cooler for the money. I don't know for sure if it will fit your card but you can try:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

There is also no guarantee that you can fit it in your case. But it works well. I have read reviews of people using it with their 4850s and 4870s to lower idle temps by 40 degrees Celsius. That huge.
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