4850 + 4870 X2 crossfire possible?

[TommyD]

Can you hook up a 4850 and a 4870 X2 in Crossfire?

From what I can see in pictures the 4870 X2 only has 1 crossfire bridge where the 4850 has 2. So I myself i'm not sure.

Anyone know?

 

[FalseChristian]

No, I don't think so. Not yet, anyhow. I believe you can mix 2 cards from different manufacturers such as, say, Powercolor and Sapphire from the same generation (2 4870s, for example.).

 

[nonameo]

I am pretty sure you can crossfire anything from the same family.

 

[apoppin]

Originally posted by: TommyD
Can you hook up a 4850 and a 4870 X2 in Crossfire?

From what I can see in pictures the 4870 X2 only has 1 crossfire bridge where the 4850 has 2. So I myself i'm not sure.

Anyone know?

yes, but it would be really silly

You would limit your X2 to the 4850's speed and performance

as soon as i am done with my regular benches, i am going to try HD4870x2 + 4870/512MB in X3 and see if the framebuffer - now limited to a total of 512MB - down from the X2's 1GB - will perform

 

[MarcVenice]

Really apoppin? I don't even own a nvidia videocard, but you can use a HD4850 and crossfire it with the IGP hd3200, and I'm sure as hell the HD4850 won't clock down to the IGP's speed. Hybrid stuff. Not sure how it works with the higher-end though.

 

[firewolfsm]

apoppin, you're usually pretty reliable for answers, what happened?

The ONLY thing that could limit performance or slow cards in XFire is differences in frame buffers, and IIRC, the X2 has 1GB total, so 512MB per card, in which case any 512 card would work. If one card is slower than another, the faster one will just render more frames than the other, matching the ratio between their clock differences usually.

However, that's theoretically, I've seen this system set up and it didn't work as well as it could. It was faster than just a 4870 X2 but not much.

A 4870X2 + 4870 should work better with no penalties.

 

[Sylvanas]

The two cards will run at their standard clocks, they will not 'down clock' one card to the others speeds- and they be fine in Crossfire. However, the framebuffer will be limited to the lowest common denominator, which would be 512mb.

Really apoppin? I don't even own a nvidia videocard, but you can use a HD4850 and crossfire it with the IGP hd3200, and I'm sure as hell the HD4850 won't clock down to the IGP's speed. Hybrid stuff. Not sure how it works with the higher-end though.

The high end cards cannot Crossfire with the IGP, there is simply too big of a disparity there- the 3450 is the highest you can go that will Crossfire with the IGP. This could of course all change with Lucid's Hydra 100 though

 

[bryanW1995]

Originally posted by: firewolfsm
apoppin, you're usually pretty reliable for answers, what happened?

The ONLY thing that could limit performance or slow cards in XFire is differences in frame buffers, and IIRC, the X2 has 1GB total, so 512MB per card, in which case any 512 card would work. If one card is slower than another, the faster one will just render more frames than the other, matching the ratio between their clock differences usually.

However, that's theoretically, I've seen this system set up and it didn't work as well as it could. It was faster than just a 4870 X2 but not much.

A 4870X2 + 4870 should work better with no penalties.

sorry, you're wrong. the 4870 x2 is 2gb total, undboubtedly because the 512mb ram was limiting its performance on 30" monitors. Also, amd has clearly stated numerous times that you CAN xfire 4850 and 4870, but they have also been very clear that the crossfire solution will only perform as well as the weakest card in the system. apoppin has done this before, too, so if we had any doubts we could always just take his word for it.

 

[apoppin]

Originally posted by: firewolfsm
apoppin, you're usually pretty reliable for answers, what happened?

The ONLY thing that could limit performance or slow cards in XFire is differences in frame buffers, and IIRC, the X2 has 1GB total, so 512MB per card, in which case any 512 card would work. If one card is slower than another, the faster one will just render more frames than the other, matching the ratio between their clock differences usually.

However, that's theoretically, I've seen this system set up and it didn't work as well as it could. It was faster than just a 4870 X2 but not much.

A 4870X2 + 4870 should work better with no penalties.

first of all, my X2 has 2GB DDR5 - the framebuffer is 1GB and if i use a 4870/512M or a 4850/512MB, the total shared framebuffer will be limited to 512M instead of 1GB. That will definitely limit you at higher resolutions - compared to a 4870x3 with 1GB of framebuffer

as to 1GB 4850, the performance increase will still be less than running with a 1GB 4870 as the 2nd card.

As to what happens when we put a 4870/512M with a 4870x2/2GB, let's find out what happens. i intend to do this very thing. i am sure there will be some penalty at 19x12 in some games. i do not know how well this will scale nor will i know the extra potential possibly gained with a 1GB 4870 as the 2nd card.

There was some penalty running a 256bit 2900pro overclocked to 2900xt speeds with a 512bit 2900xt. i am basing my answers on this - that a 4850 will limit performance somewhat over choosing a 4870 as the 2nd card - CrossfireX is still rather imperfect, you know