7970GHz xfire R9-280X

tej789 · Apr 10, 2014

I currently own a Sapphire 7970 GHz Edition Vapor-X with 6GB of Ram. If I were to buy an R9-280X and crossfire them, I believe that is possible, how much combined memory would I have? Would I have 9GB of memory or would the drivers only show a total of 6GB by blocking 3GB from the 7970 to make them more similar?

RobCrezz · Apr 10, 2014

In crossfire it would cap the 2970 to the same amount as the other card, so you would have 3gb total usable vram as it doesnt stack as the cards cannot share the vram.

cdrkf · Apr 10, 2014

tej789 :

RobCrezz :

+1 to this, you'd be better off getting another Saphire 7970 6gb card if you can find one. I'm not sure if any custom 280X cards have been released with 6gb yet.

Even if you do this you'll still only get 6gb available as RobRezz said the ram doesn't add together. Having said that I very much doubt you'll have any use for more than 6gb vram (the amount needed depends on the resolution you're playing at- 4k can use just over 3gb in some games as can an eyefinity set-up e.g. using 3 x hd screens).

tej789 · Apr 10, 2014

cdrkf :

tej789 :

RobCrezz :

+1 to this, you'd be better off getting another Saphire 7970 6gb card if you can find one. I'm not sure if any custom 280X cards have been released with 6gb yet.

Even if you do this you'll still only get 6gb available as RobRezz said the ram doesn't add together. Having said that I very much doubt you'll have any use for more than 6gb vram (the amount needed depends on the resolution you're playing at- 4k can use just over 3gb in some games as can an eyefinity set-up e.g. using 3 x hd screens).

Did the way xfire handles memory change recently? I used to have two 1GB 5850s and when crossfired it shows me as have 2GB of video memory.

cdrkf · Apr 10, 2014

tej789 :

I believe it reports the total memory added together- like the new R9 295X2 has '8gb of ram'- well technically yes it has 8gb, however due to the way crossfire (or sli for that matter) work you can only use as much memory as is on one card or gpu.

The reason for this is that the system works using a technique called 'AFR' (Alternate Frame Rendering) where the 2 cards render frames alternately- so all the information for the whole image has to be in memory on both cards at the same time.

tej789 · Apr 10, 2014

cdrkf :

tej789 :

I believe it reports the total memory added together- like the new R9 295X2 has '8gb of ram'- well technically yes it has 8gb, however due to the way crossfire (or sli for that matter) work you can only use as much memory as is on one card or gpu.

The reason for this is that the system works using a technique called 'AFR' (Alternate Frame Rendering) where the 2 cards render frames alternately- so all the information for the whole image has to be in memory on both cards at the same time.

Ah ok. Now I understand. Thanks for clarifying. So I am probably better off trying to find another 6GB 7970 to have max amount of ram, than cutting the one card in half.

RobCrezz · Apr 10, 2014

tej789 :

cdrkf :

Did the way xfire handles memory change recently? I used to have two 1GB 5850s and when crossfired it shows me as have 2GB of video memory.

No. It still may report the combined vram, but in practice you will only have the usable amount of the card with the smallest amount, in your case 3Gb.

cdrkf · Apr 10, 2014

tej789 :

cdrkf :

tej789 :

I believe it reports the total memory added together- like the new R9 295X2 has '8gb of ram'- well technically yes it has 8gb, however due to the way crossfire (or sli for that matter) work you can only use as much memory as is on one card or gpu.

The reason for this is that the system works using a technique called 'AFR' (Alternate Frame Rendering) where the 2 cards render frames alternately- so all the information for the whole image has to be in memory on both cards at the same time.

Ah ok. Now I understand. Thanks for clarifying. So I am probably better off trying to find another 6GB 7970 to have max amount of ram, than cutting the one card in half.

Yes exactly.

tej789 · Apr 10, 2014

cdrkf :

tej789 :

cdrkf :

tej789 :

I believe it reports the total memory added together- like the new R9 295X2 has '8gb of ram'- well technically yes it has 8gb, however due to the way crossfire (or sli for that matter) work you can only use as much memory as is on one card or gpu.

The reason for this is that the system works using a technique called 'AFR' (Alternate Frame Rendering) where the 2 cards render frames alternately- so all the information for the whole image has to be in memory on both cards at the same time.

Ah ok. Now I understand. Thanks for clarifying. So I am probably better off trying to find another 6GB 7970 to have max amount of ram, than cutting the one card in half.

Yes exactly.

Thank you.

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