ATI vs Nvidia motherboards?

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Hi guys,

Im working on my first build here, and I have a pretty simple question
but I would still like it explained to me. I was looking at [asus]
motherboards and I noticed that there are different types of
northbridges for different motherboards, nvidia specific and ATI
specific.  I was wondering what would happen if I were to plug in an
ATI card into a SLi specific board; or vice versa, a geforce in a
crossfire board.  They are both PCI express, so I know that they will
"fit" in any of these motherboards, but I know it cant be as simple
as putting a square peg in a square hole when they specifically tell
you which video card works best.


Re: ATI vs Nvidia motherboards? wrote:

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Bus standards are designed to be device agnostic. The AGP standard
was a tough environment to design in, and many companies did a poor
job of designing an interface that would work. Consequently, stupid
rumors would spread, about a lack of interoperability, with some
of the AGP slots.

PCI Express was a clean slate, and a chance for the terrible qualities
of some AGP slots to be expunged. You should be able to plug an
ATI card into an Nvidia slot, or an Nvidia card into an ATI slot,
and get basic video card functionality. Even some of the lesser
chipset companies have managed to build PCI Express slots that

If you are trying to do Crossfire on an SLI motherboard, or SLI
on a Crossfire board, then the drivers may enforce whatever arbitrary
policy the respective companies want. The only property I'm aware
of, is I think Crossfire requires the ability of one video card
to do a bus master write to the other video card. And while I
would have expected all chipsets to support that, maybe there are
some that don't. In any case, the lack of universal support
for SLI/Crossfire is more of a business decision than a
technical one.


Re: ATI vs Nvidia motherboards?

Paul wrote:
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Okay, thanks Paul, youve helped me out a lot. You seems to agree that a
single card will work in any motherboard no mater what chipset I have.
So my questions is, is the Northbridge chipset only utilized when two
graphics cards are plugged into the on the board? does a crossfire
chipset run an ATI card better than a nforce? (or the vice-versa)

Re: ATI vs Nvidia motherboards? wrote:

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Whether a Northbridge has one video card slot or two video card
slots, it still does not favor one brand of card over another.

Brand favoratism is established by the drivers. If Nvidia doesn't
want two video cards to run in SLI on an ATI chipset, the driver
can figure that out. Similarly, if ATI wants to stop a pair
of ATI cards from running in Crossfire on an Nvidia chipset,
their driver could stop that too.

There are some hardware dependencies for operating two video cards.
So even if there were no restrictions in the drivers, there may
be video card schemes that won't work on all chipsets. One requirement
I have heard of (in fact the only one), is the chipset is required
to support a bus master write from one video card, into the other
video card. I expect that is for Crossfire, but I could be wrong
about that. But details like that were never explained in any
enthusiast web sites, so it is hard to point out things to look for.
And I'm not sure any chipset datasheets explain whether features
like that are present in a chipset or not.

At the current time, the drivers apply more restrictions than
the hardware does.

If you are using just one video card, you have nothing to worry about,
because in that case, the two video card companies are more interested
in all of their products just working. If any "dirty tricks" were played,
and someone figured that out, the company playing the dirty tricks
would lose a lot of business from the backlash. The hardware labs
at ATI and Nvidia would be perfectly capable of detecting whether
their competitor was playing tricks or not.


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