What is SLI ?

What is SLI ? · 20-05-2008, 10:48 AM

Hello Friends

1. What is SLI?
2. And is there any relation (video card) among RAM (DDR2 DDR 3 etc)
3. Is this technology built-in in today’s motherboards? (Any example model)

Thanks

Fu3|3D® · 20-05-2008, 11:14 AM

Scalable Link Interface - Wikipedia, the free encyclopedia

kashif99048 · 20-05-2008, 11:27 AM

dont fully rely on wiki though.........

try nzone.com also

kashif99048 · 20-05-2008, 11:31 AM

this is the official sli site .............SLI Zone - Gaming PC, Gaming Computer, Build a PC

FORUM

kashif99048 · 20-05-2008, 11:32 AM

and most of all............u must see this

How to Build a PC - Video Guide to Building a PC

ali.tayyab · 20-05-2008, 12:05 PM

1. Scalable Link Interface

This is how it works:
It uses two or more gpu's to render what u see on screen. It works in 2 modes:

a. Split Frame Render:
It splits the frame (what u see) horizontally in two 2 parts. The division is not at the center. the division is such that the load on both gpu's is the same. if for example a night scene is shown, the top half is basically just an open sky. thus not much to render. the bottom half has the most objects. if the frame was divided in the center, one card would do next to nothing (rendering top half), the other would do most of the work. In this case the division would be much lower, so as keep load balancing as near as equal between the gpu's

b. Alternate Frame Render:
This is simpler to understand. Each card renders an alternate frame. One card would render frames 1,3,5 the other 2,4,6. in a three card situation it would be 1,4,7 next card 2,5,8 the third card 3,6,9 and so on. This is obviously better than #1.

U can use AA with SLI. it doesnt improve speed, but improves the level of AA. e.g. if single gpu does 8xAA, two would do 16xAA, four would do 32xAA and so on.

the nvidia GX2 and ATi X2 series use one card, but apply SLI (or crossfire for ATI) to double the gpu count. using 2 of these gets u 4 gpu's. using 3 of these gets u a massive 6!

There is something called hybrid SLI. it uses a gpu onboard a motherboard and one u plugged in. The results are bad, as the SLI defualts to the speed of the slowest gpu, which is the on onboard the motherboard. this is present on specific nvidia based boards

2. RELATION TO RAM:
SLI needs two identical cards at identical specs and speeds. If the speed isnt the same, SLI works at the speed of the slowest card. The amount of ram can be different, but again the cards will work and use only the least amount of ram: the cards must be of the same generation e.g. g80, g92 etc

e.g.
Card 1: 8800GTX Core: 575, RAM: 900
Card 2: 8800GTX Core: 600, RAM: 1000

the SLI config would use: Core: 575, RAM: 900

e.g.
Card 1: 8800GT Ram: 1 Gig Core: 600 RAM: 1000
Card 2: 8800GT Ram: 512MB Core: 650 RAM: 1200

SLI: RAM: 512, Core: 600 RAM: 1000

The type of ram isnt of concern. though one gen tends to use the same type of ram.

3. MOTHERBOARDS
U need a nvidia chipset board to get SLI. some early nvidia drivers (very old now) allowed a hack which made SLI work on anyboard with 2x pci-e x16 slots (mechanical, electrical they can be x16, x8 or x4). This isnt true anymore

nvidia chipsets that do support SLI and the latest intel cpu:
1. 790ultra
2. 790i
3. 750i

the ultra uses ddr3, the 790i uses ddr2.
the 750i has x8,x8 SLI slots.

4. WHAT IS x16, x8, x4

Pci-e slots have "lanes" which allocate bandwidth to them. the more the lanes, the greater the bandwidth.

the configuration depends on how many pci-e lanes a mobo chipset allows:

790ultra allows x16, x16 on pci-e x16 slot.
790i allows the same
750i allows x8,x8

As u can see the slot might be physically a x16 slot, i.e. long, but it might not get as many lanes. this truer of many intel Corssfire boards where the division is usually x8, x4.

if u plug in one card in one slot on 750i for example the slot can use lanes for both slots i.e. it becomes a x16 slot

Do extra lanes matter:
firingsquads review of 750i shows that x8,x8 is as good as x16,x16. U need to have games to consume ultra uber amount of bandwidth to choke these 8 lanes. with SLI u divide up the work and also apply a SLI bridge which allow alternate pathway for data to get through. if u have weaker cards (6 series or 7 series) u can do without the SLI bridge as the pci-e lanes are enough.

hope this helps!

mave_3 · 20-05-2008, 12:49 PM

apart from what ali has said...
here are to links that can also help..

What is SLI

and the other one is youtube link :

YouTube - Build a PC - Step 1 - What is SLI?

OmMeE · 20-05-2008, 01:00 PM

This forum ROCKS!!!!

mave_3 · 20-05-2008, 01:14 PM

ohh yes it does

no doubt in that

Fu3|3D® · 20-05-2008, 01:22 PM

ali tayyab correct your above post
there are corrections in it

20-05-2008, 10:48 AM	#1
What is SLI ? skywalker Member Join Date: Dec 2007 Posts: 51 skywalker 20-05-2008, 10:48 AM Rating: () Hello Friends 1. What is SLI? 2. And is there any relation (video card) among RAM (DDR2 DDR 3 etc) 3. Is this technology built-in in today’s motherboards? (Any example model) Thanks Last edited by skywalker : 20-05-2008 at 10:52 AM.
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