SLI / CrossFire FAQs

[meodowla]

No,the 9600 card is used as a PhysX card.

Yeah.. So is it possible that i could use my onboard nVidia 8300 as PhysX card and ATi HD4850 as primary...?
(Note: My board support Hybrid SLi)

 

[Maziar]

I dont think you can(i am not sure though)

 

[Maziar]

Edit:Read this
http://forums.guru3d.com/showthread.php?t=281801

 

[meodowla]

From Guru3D Forum:

This driver will help do it possible:
http://www.donotargue.com/dna_hybrid/DNA-ATi-Hybrid_Vista_8.12x64.exe

 

[meodowla]

This is not SLi..... but PhysX........

 

[Decibel]

hello Maziar..
Thanks for all the info on crossfire..very insightful.....I was having problem myself to understand how to get most from my mobo crossfire potential... I need your help to find a good but not very expensive video card from my Asus P5Q Pro...it seems to me you really know this stuff...I have BFG 8400 GS, but i would really upgrade it to something more powerful for my gaming experience....I have a dual CPU, 2GB memory ram ddr2, 300GB hard disk.
Thanks Maz...I appreciate..Decibel

 

[Maziar]

Hello mate glad you found this useful
Well asking about which card to get is in this thread:
http://www.tomshardware.com/forum/169937-33-short-list-gaming-videocards-money

 

[Decibel]

hey thanks....you would not believe but i am registered on that forum! ...Good eh!! But i would like to have your opinion, what you think i should do!!!!Because you mentioned few of the Asus mobos previously, i was wondering if you could gave me an hint of which graphic card would do good on my pc.... i appreciate Maz....Thanks for the heads up about tom hardwareweb..... 😉

 

[OMGiTzzFATAL]

Hi, i have a question:
im looking to go crossfire with 2xHD4870's, i already have one at the moment and im looking to get another one, my current card is 512MB, and im going to get another 512MB card. Will i see any performance gain if a game wants more than 512MB of memory? (am i write in thinking that the memory from both cards will NOT be combined ?)

Ive looked on some benchmarks and ive seen that the 1gb card does better than the 512MB card when the game wants more than 512MB's, also when the resolution is high and theres AA and AF enabled.

I have a second question:
If i get the 1GB version and use it with my current 512MB card in crossfire, and use the 1gb card as the primary card will my memory be 1GB?, or will it go down to 512mb?

please help im so confussed >.<

P.S i game @ 1920x1080

 

[Maziar]

to decibel:
I dont know your budget but an ATI HD 4850/4870 would be good for you.

to OMG:
Hello mate
Well first of all,the difference between 1GB cards and 512MB cards aren't much son don't worry much about it.also when you combine 2 HD 4870s cards which both have 512MB memory,you still will have 512MB memory,as multiGPU won't double the memory.


About mixing a 512MB 4870 with a 1GB 4870 ,read this thread:
http://forums.guru3d.com/showthread.php?p=2935216

5. What happens when graphics cards with varying memory speeds and engine clocks are paired together?

A. In this scenario, overall performance will be adjusted to match the memory speeds and engine clocks of the lower clocked card. To obtain ideal performance, graphics cards should be paired correctly.

If u alreayd haven't purchased your VGAs,go for 1 HD 4870X2 instead,because it has an overall better performance,i myself have the same monitor like you and went for HD 4870X2,because its basically 2 HD 4870's on one card but it produces less heat,requires one slot and has better performance in some cases.

 

[OMGiTzzFATAL]

ok thanks, thats really helpful
😀
ill check out that link now

 

[OMGiTzzFATAL]

ok just read the link you gave me.

but i still have a problem, by the sounds of it, if i crossfire 2x4870 512 ill only have 512mb of memory so i still will not be able to go to 1920x1080 with AA and AF on am i correct?

is it going to be worth it for me?

your help would be much appreciated!!!

 

[Maziar]

Who says you cant ? you can enable AA and AF.

 

[OMGiTzzFATAL]

yeah of course, but because its a 512mb card it cant handle it well. i turn on AA and AF on farcry 2 and my FPS goes out the window >.<

 

[Maziar]

Does that happen in other games?
Do you have the latest VGA drivers installed?

 

[OMGiTzzFATAL]

yeah ive got 8.12

well i can play fallout 3 with al the bells and whistles (8xAA and 15xAF samples).

urrr obviously crysis kills my hole system

GRID i ran play on max with everyytihing on.

COD4 i can play on max with AA and AF max @ 1920x1080

it seems to be the newer, more demanding games that my card doesnt handle well.

 

[Maziar]

If you dont have problems with GRID and COD4,then there isnt a problem with your card,your card is a solid card who says your card can't handle games with it? about Crysis,its strange,however adding AA with 1920x1080 resolution won't make alot of difference since it doesn't have noticeable jaggies.
I tested it myself.

 

[OMGiTzzFATAL]

ok, but my question still remains, will i see noticable difference if i were to crossfire with another 4870 512mb card when playing @1920x1080 with AA and AF on?

Also if i were to crossfire with a 1gb card and use it as my primary card will i then have 1gb of video memory?

 

[Maziar]

1_Yes you will get a decent boost in FPS,since you play at a high resolution.but i again say this:90% of games won't need AA for 1920x1080 resolution,because you won't see a lot of jaggies.

2_I answered you if you crossfire a HD 4870 512MB with a HD 4870 1GB,you will have 512MB still,read my postes above.

 

[meodowla]

So.. 4870 1GB would be recognised as 4870 512MB by its CrossFire partner 4879 512MB???

 

[meodowla]

++type mismatch..read last as 4870

 

[nukemaster]

For crossfire it would only use the first 512MB's of memory. The card would still have all the ram, but not be able to use it

In crossfire BOTH cards always hold the same textures and information. As such it will have to go with the memory of the lowest card(512). If the card was on its own it would have both.

 

[Maziar]

nuke is right.
The card still has 1GB memory but uses 512MB when its in CrossFire(when a 4870 512MB is CrossFired with 4870 1GB)

 

[terr281]

(Sorry if this is mentioned earlier, but this post is extremely long.)

Notes:

1. I would distinguish between the 680i and the 680i lt MB, in regard to the 3-way SLI and duel x16 lanes. The 680i lt has 2 PCI-E x16 slots, so it can't 3-way SLI...but does have the duel x16 lanes.

2. You may or may not want to include a note regarding 8800 GT and 9800 GT video cards being "the same," and thus being able to SLI them together. (I know the difference is in the BIOS... and the manufacturing process of "new" 9800 GTs...thus Hybridpower support.) For the common user, they can't be SLI'ed together. However, if someone wants to risk flashing the bios of one of the cards, they can be SLI'ed. (I am not one of those people to risk it though.)

3. You may want to include a note regarding PCI-E 1.0/1.1/2.0 as well.

 

[Maziar]

This things that you mentioned are mostly for motherboards but i will add some of them.

1_That was necessary i added it,thanks

2_You can't SLI a 8800GT with 9800GT,but with hacking its other story,you can do many things with hacking but its not recommended and it may hurt the cards too.

3_Thats not very related to SLI/CrossFire, about motherboards,i mention which chipset support MultiGPU and in which ways and things like this,my main focus is on MultiGPU technology and VGA cards not on motherboards.

However thanks alot mate