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View Full Version : True x16 SLI, which one is true and which one is not


justinamanzer
04-06-06, 02:48 AM
Hi

im an sli noob and i am about to build a system that is sli enable. Ive been looking through several motherboards and found that each of them have several differences on the lanes of pci-e.

i also found out that on some motherboards if SLI has been enabled the bus speed that the graphics card will run is only in 8x and not use 16x not the full lane. they say that the 2 x16 pci-e will share the 16 lanes to 8. is this true? if so are there motherboards that will run in true x16 using the full 16 lanes and not share the 16 lanes if sli is enabled?

MUYA
04-06-06, 02:52 AM
Yes there are two SLI chipsets

The nForce 4-SLI which has two graphics port and when both are occupied, will run at PCI-e x8 each

Then the nForce4-SLI32 or something, that also has two graphics port but unlike the chipset above, each card on each graphics port will run at 16x PCI-e.
Actually benches show no much difference between them except when using SLI AA.

Dazz
04-06-06, 03:32 AM
At the moment there is no true dual PCI-express chips bar the ATi 3200 chipset.

Digital_Trans
04-06-06, 04:12 AM
True x16 PCI Express Support is here! Get an Asus P5N32-SLI Deluxe motherboard. I'm using it and it supports full x16 PCI Express in single lane and in SLI mode. (nana2)

MUYA
04-06-06, 04:43 AM
Thats right the poster hasn't mentioned which AMD or Intel platorm he intends to build his SLI system.

justinamanzer
04-06-06, 05:27 AM
yes full x16 support is available so i guess u have a virtual x32 bus support in sli mode. found it out after doing some research.

SLI™ mode supports:
- 2 x identical SLI™-ready PCI Express™ x16 graphics
cards (Note: In SLI mode, the PCI Express x16 slots work
at the full bandwidth of x16 each, for a combined
bandwidth of x32.)
ASUS Soft SLI Bridge
ASUS EZ Plug™
ASUS PEG Link for dual PCI Express graphics cards
ASUS Two-slot thermal design

Its an asus A8N32-SLI_Dlx

thanks for the info guys

MUYA
04-06-06, 05:50 AM
At the moment there is no true dual PCI-express chips bar the ATi 3200 chipset.
U might notice he was asking for SLI and nor crossfire solutions? K thanks

Venturi
04-06-06, 08:31 AM
justinamanzer:



The tyan thunder s2895, the s4885, and the some of the 3xxx series have true individual 16x slots. The s2895 lets you also control other SLI features right in the bios no hardware switches or jumpers.

I have built and run on both boards.

MUYA is correct on the performance variance being low. However, there is a 10-15% hit on performance at 2560x1600 SLI if you lower the slots from 16x to 8x.


Also you have to select an SLI MASTER card in the bios so that additional throughput can be allocated on the motherboard and chipset for the card that actually connects to the monitor. The second card then becomes the SLI SLAVE. This will also boost performance by 5-7%.

2nd Also, you have to define in the bios the amount of LANES on the hypertransport bus and the speed that they perform at in relation to which CPU is going to feed which GPU and if the requests can go between the GPU's bus.

My experience with SLI is limited to dual or quad cpu boards, maybe there are other tweaks on different boards.


JV

The Bigman
04-06-06, 04:02 PM
Im new to SLI, i heard there some tweaks in the bios even on the 32x boards to optimize sli in games changing values.

Im still comfused about the vsync option. I leave it at auto and i get SLI in FarCry to work seeing the green bar at the left of the screen, but if i enable ot totally i get no SLI or no green bar in some games but in others.

People claim to leave it to Auto but when i choose FR2 Frame Rendering 2 i get good game performance.

The secrets of SLI would be good to know if you have a guide and i don't see any good guides to SLI.

OWA
04-06-06, 05:25 PM
The load balancer usually doesn't show up if vsync is enabled although SLI is still supposed to be working. Just remember, if you use vsync, your framerate is capped at your refresh rate. So, if you're using a LCD with a refresh rate of 60, you'll never see above 60fps, if you're using a CRT with a refresh rate of 85, you'll never see above 85fps, etc. If you don't get a lot of tearing, leave vsync off.

Fathertime36
04-06-06, 05:55 PM
It is kind of a mut point anyway, at least right now no applications makes use of the bandwidth gained through a true 16x16 pcie port, so until things changes you are paying a premium for what is essentially overkill.

justinamanzer
04-06-06, 10:46 PM
justinamanzer:



The tyan thunder s2895, the s4885, and the some of the 3xxx series have true individual 16x slots. The s2895 lets you also control other SLI features right in the bios no hardware switches or jumpers.

I have built and run on both boards.

MUYA is correct on the performance variance being low. However, there is a 10-15% hit on performance at 2560x1600 SLI if you lower the slots from 16x to 8x.


Also you have to select an SLI MASTER card in the bios so that additional throughput can be allocated on the motherboard and chipset for the card that actually connects to the monitor. The second card then becomes the SLI SLAVE. This will also boost performance by 5-7%.

2nd Also, you have to define in the bios the amount of LANES on the hypertransport bus and the speed that they perform at in relation to which CPU is going to feed which GPU and if the requests can go between the GPU's bus.

My experience with SLI is limited to dual or quad cpu boards, maybe there are other tweaks on different boards.


JV

venturi

on your sig do you have a tiger k8we 2895 or thunder k8we 2895. in tyans website they advertise that the thunder k8we 2895 pci-e x16 slots both of them run at full speed x16 is that what your setup is

thanks

Q
04-06-06, 10:51 PM
Other than paying out of the ass for true x16 SLI, you have to deal with two other major issues: heat dissapation and power usage. The reason for this is because the NF4 boards have to run two chipsets to manage these lanes. They use about 60-80w more power and as a result throw a lot more heat into your case.

The Bigman
04-06-06, 11:38 PM
Ouch, thats alot for MB. IS it confirmed about the stickers on the chipset heatsinks with the A8N32 mobo? Removing them lower the temps?

Dazz
04-07-06, 01:33 PM
There is no true 16x SLi board as they use both Intel & AMD NF chips in one board then connected via a 800MHz x2 (1600MHz) HTT 8bit = 1.6GB/sec bandwith to comunicate from video card to video card but has full PCI-E speed.