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3870 crossfire with 3870x2?

D

Decko

2[H]4U
Joined
Sep 23, 2007
Messages
3,660
I saw that you can crossfire a 3870 and a 3850. Now what I want to inquire is whether or not a current 3870 would crossfire with a 3870x2 in some odd Tri-Crossfire configuration? What do you guys think?
 
There will be more information soon regarding the Quadfire and related information once the "dual 670 boards" become released.

Which hopefully will be soon -_-

I can't wait to see how things stack up when the production boards hit the streets and the drivers get moving.
 
Well if you look at the recent pictures on hardocp it looks like they only require one crossfire connector. Does it show them using two crossfire connections? That doesn't really make sense to me because they're on the same pcb. Am I mistaken, I don't claim to be a hardware guru, but it doesn't seem like it would require that kind of interfacing. Any other thoughts? Of course this is all theoretical, it depends on drivers and a lot of other variables we don't have any information about... so let's just have fun with it.:)
 
on current crossfire, yeah you only need the 1 bridge. There are beta rigs (for lack of a better term) where ati has 4X 3870's running in crossfire on an RD790 (marketed as 790FX i believe), Card A is connected to card B, B is connected to card A and C, C is to B and D.

I just want mixed card multi GPU configurations. The drivers currently devide the load up on a card-based level. Card 2 needs to be in sync with card 1. To achieve mixed card SLI we need pipe based sync'in (of course that requires a solid definition of what a pipe is, we keep changin em).
 
oh okay I see how that works, and it's pretty interesting I'd very much like to see what kind of overall performance. I guess I should of wrote my original post more clearly to ask the question i'm looking to get some sort of possible answer even though the tech isn't available. Does anyone think one 3870 would work in crossfire with one 3870x2? I guess saying tri-crossfire was the wrong term, but technically it would be 3 cards running together. Any thoughts?
 
Decko87 said:
oh okay I see how that works, and it's pretty interesting I'd very much like to see what kind of overall performance. I guess I should of wrote my original post more clearly to ask the question i'm looking to get some sort of possible answer even though the tech isn't available. Does anyone think one 3870 would work in crossfire with one 3870x2? I guess saying tri-crossfire was the wrong term, but technically it would be 3 cards running together. Any thoughts?
Click to expand...

Morfinx, care to chime in? :p
 
Decko87 said:
oh okay I see how that works, and it's pretty interesting I'd very much like to see what kind of overall performance. I guess I should of wrote my original post more clearly to ask the question i'm looking to get some sort of possible answer even though the tech isn't available. Does anyone think one 3870 would work in crossfire with one 3870x2? I guess saying tri-crossfire was the wrong term, but technically it would be 3 cards running together. Any thoughts?
Click to expand...

i think its feasible, afterall, its 'three hd 3870 cores' ya? so the tri-fire makes sense. oh and don't worry, I had the exact same question as you so I'm glad you posted this. In another thread,
http://www.hardforum.com/showthread.php?t=1242305&page=3
Cablespider posted a link to the online manual of the HD 3800 series and it claims that crossfire 'does' work with one of the connectors. If that's the case then I can see tri-fire working with a HD 3870 x2 and a regular HD 3870.
 
Hey, the 38xx cards are PCI Express 2.0 right?
So do you need an X38 board to take advantage of CrossFire, or will P35 or any earlier chipset do?

Thanks!
 
Both the X38 and P35 support crossfire.
However, some P35 boards only have 1 PCI-Express x16 slots, which takes away the possibility of crossfire with 2 physical cards.
 
X38 are the only ones with full x16 lanes otherwise CF on a 2 x16 PCIE P35 is going to have one at x4 and another one at x16

How much that matters, I don't know

PSU requirements? Too early to tell, but supposedly it'll be the same as having 2900XT's in CF so i'd say you'll want a 600+watt PSU to be safe.
 
ZerazaX said:
PSU requirements? Too early to tell, but supposedly it'll be the same as having 2900XT's in CF so i'd say you'll want a 600+watt PSU to be safe.
Click to expand...

OK thanks. I've got a new Antec 550W PSU lying around. Should it not be able to cut it?
I mean, they only take 1 PCI Ex connector each.
 
CF x 3870 probably in the neighbourhood of 750w, since these cards use less power than the previous R600's.

In Hardocp's review they also have information regarding the load power draws.
 
R1ckCa1n said:
Maybe for two 3870x2 cards but not for two 3870's.
Click to expand...

Agreed, 750W for just two 3870s sounds high.
According to H's tests, the total system load (under full load) was 268W with one card. I know one needs overhead and all, but I have trouble seeing 750 watts being needed.

Wish we got a statement from AMD on this tho..

edit: fixed typos
 
CC_Pirate said:
Agreed, 750W for just two 3870s sounds high.
According to H's tests, the total system load (under full load) was 268W with one card. I know one needs overhead and all, but I have trouble seeing 750 watts being needed.

Wish we got a statement from AMD on this tho..

edit: fixed typos
Click to expand...

What, like a list of certified PSUs?

http://ati.amd.com/technology/crossfire/buildyourown2.html

Looks like the PSU I'm using (Enermax Liberty 620W) for two X1900s will work fine. Interesting as it isn't certified for 2900s, showing a definite improvement in power consumption.
 
Do you need an ATI/Intel chipset to run one 3870x2? I assumed it would function like the 7950X2 where it would work with any pci-express board. I'd consider getting a 3870X2 to play with but all my computers are running nvidia chipsets.
 
Diseaseboy said:
Do you need an ATI/Intel chipset to run one 3870x2? I assumed it would function like the 7950X2 where it would work with any pci-express board. I'd consider getting a 3870X2 to play with but all my computers are running nvidia chipsets.
Click to expand...
No the 3870x2 is supposed to work on any motherboard
 
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