ATI HD4890 Owners Thread

[gtarmanrob]

Originally Posted by weebeast

My second 4890 is on his way! Its a black edition so it has higher speed then my first card. Will it downclock himself lower when i cf it?

By the way are the windows 7 drivers good? Or should i still stick with vista?

1 - yes unless your overclock your other card, the faster one will underclock to match specs.

2 - Windows 7 drivers are great, i've noticed better performance actually, but i only play Left 4 Dead. Lost Planet also went up a couple of frames. i upgraded to Windows 7 purely coz i wanted a new OS, i had no problems with Vista 64 from day one. imo its a worthy upgrade, above anything else it looks and feels really good.

[xxbassplayerxx]

Originally Posted by vicious_fishes

it won't downclock, and windows 7 and vista drivers are the same thing.

and the memory is not shared, it is mirrored. hence why you can crossfire a 4850 with a 4890 or whatever

So are you saying memory speeds don't have to be the same?

[weebeast]

Thanks guys i will get windows 7 when i got home

About the downclocking. My normal 4890 cant hit 1 ghz with 1,35-1,45 volt so i cant use the full potential of my second card like you guys said. Could this be based on drivers?

[vicious_fishes]

Originally Posted by xxbassplayerxx

So are you saying memory speeds don't have to be the same?

nope. as long as the first two numbers are the same, you can crossfire

cards do NOT downclock in crossfire.

[gtarmanrob]

Originally Posted by vicious_fishes

nope. as long as the first two numbers are the same, you can crossfire

cards do NOT downclock in crossfire.

...im pretty sure the higher clocked card will downclock. otherwise how do they work in unison with one running much faster than the other?

i know for a fact SLI used to downclock, with Crossfire i cant say for sure then coz all my Crossfire setups have been with identical cards.

EDIT:

im right

http://ati.amd.com/technology/crossfire/faq.html

click #5

EDIT 2:

oops i think this might only refer to Crossfire of 2 different cards IE: 4870 + 4890 or something. if you Crossfire 2 of the same cards like 4890 + 4890OC but one has a higher clock it wont underclock apparently.

[vicious_fishes]

Originally Posted by gtarmanrob

...im pretty sure the higher clocked card will downclock. otherwise how do they work in unison with one running much faster than the other?

i know for a fact SLI used to downclock, with Crossfire i cant say for sure then coz all my Crossfire setups have been with identical cards.

EDIT:

im right

http://ati.amd.com/technology/crossfire/faq.html

click #5

so why does a 4890 + 4870 do better than 4870+4870 then ?

[gtarmanrob]

Originally Posted by vicious_fishes

so why does a 4890 + 4870 do better than 4870+4870 then ?

why's the sky blue?

i dunno lol. im just providing information from what i've researched, which happens to come from the site of the manufacturer themselves.

[vicious_fishes]

it does better because the 4890 is faster and doesn't downclock. crossfire doesn't use a card to render half an image. one card does one, then the next the next and so forth.

the cards don't downclock - the faster card simply does more frames in the second than the other does. hence why crossfire gets microstuttering.

[Wishmaker]

Originally Posted by vicious_fishes

it does better because the 4890 is faster and doesn't downclock. crossfire doesn't use a card to render half an image. one card does one, then the next the next and so forth.

the cards don't downclock - the faster card simply does more frames in the second than the other does. hence why crossfire gets microstuttering.

Interesting. I had the feeling that CFX on two cards makes use of the GPU power the following way :

1. The image is split in two. One card renders one part the second the remaining.
2. If you have two identical cards, the workload will be shared equally.
3. If you have two cards in CFX but with different GPU and memory clocks, then the faster one will get tasks from the Catalyst to help the slower one.

Could you please point me in the right direction? Where did you find the article where, one card does one frame and the second another?

[vicious_fishes]

Originally Posted by Wishmaker

Interesting. I had the feeling that CFX on two cards makes use of the GPU power the following way :

1. The image is split in two. One card renders one part the second the remaining.
2. If you have two identical cards, the workload will be shared equally.
3. If you have two cards in CFX but with different GPU and memory clocks, then the faster one will get tasks from the Catalyst to help the slower one.

Could you please point me in the right direction? Where did you find the article where, one card does one frame and the second another?

http://www.anandtech.com/showdoc.aspx?i=3518&p=1

check that one out, quite informative. but no, the cards go one frame for one card, then vice-versa. ati work on a 0-1-2-0 cycle, hence why quadfire often gets less FPS than trifire.