SLI, fan and more questions about graphics cards

What's the difference between SLI and Crossfire? Are they the same
thing but different companies? Or are they technically very different?

I see pictures of many different brands of video cards. But I notice
for the same chip set most cards look *excactly* the same. They might
have different fans and different colored boards but circuit layout
looks exactly the same. What's going on? See most GS7900 cards...

Are fans on graphics card replaceable? Let's say I got a noisy fan on
a graphics cards - are there after market replacements?

Thanks

jaquas@gmail.com wrote:
> What's the difference between SLI and Crossfire? Are they the same
> thing but different companies? Or are they technically very different?

http://en.wikipedia.org/wiki/Scalable_Link_Interface

http://en.wikipedia.org/wiki/ATI_CrossFire

>
> I see pictures of many different brands of video cards. But I notice
> for the same chip set most cards look *excactly* the same. They might
> have different fans and different colored boards but circuit layout
> looks exactly the same. What's going on? See most GS7900 cards...

A reference design from the GPU chip manufacturer, can be copied by
any video board company. In some cases, the boards are centrally
made, and indeed, the only distinguishing feature, is a custom
cooler. Only occasionally is a video card designed from scratch.

>
> Are fans on graphics card replaceable? Let's say I got a noisy fan on
> a graphics cards - are there after market replacements?
>
> Thanks
>

The frames of some fans, are part of the heatsink. In other cases, the
fan assembly (square) is removable. I haven't seen too many separate
fans suitable for use on a video card, for sale. The most likely solution,
is buying an aftermarket heatsink and fan as replacement. Some form factors
make finding a replacement cooler more difficult, such as bridged AGP cards
(with the separate HSI or Rialto bridge chip that converts a PCI Express
GPU for use on the AGP bus), or low profile cards, like the PCI ones used
in HTPCs. Only a certain number of video card models, have replacement
cooling assemblies made by Zalman, ArcticCooling, and others.

Paul