Stupid question Can Crossfire a HD5870 1GB with a 2GB edition without any problems?

[lotusvibe]

Hello sorry for such a newb question, but I have a Vapor X HD5870 1GB edition and i was wondering if i could get the 2GB Vapor X edition and run a crossfire setup without any major problems. I believe they say that you can mix cards with ATI as long as there the same class but even if that's true i could imagine there might be alot of unforseen issues that could perhaps occur and possibly be avoided if i went with another 1GB and had two the exact same cards for crossfire. thoughts?

 

[ModestGamer]

you'd want the bigger ram card to be card 0 or 1 depending on the numbering scheme. IE you want the card with the most ram to be the primary card. ATI spells out the various connections and setups for the card on their website. IIRc all 5xxx series cards in the same family Ie 56xx 57xx 58xx can be easily crossfired.I think you can even mix and match some 5xxx series cards like a 5750 and a 5770 or a 5770 and a 5850 etc ec etc an nauseum. How good are the drivers ??? also depends on the game IIRC.

 

[toyota]

why would you buy a 2gb version when you are going to be limited to only 1gb by your other 1gb card anyway?

 

[OCGuy]

It will be the same as 2 1GB cards.

Although to be honest, there is no difference between 1 and 2GB on a video card right now anyway. Unless you are doing "eyefinity" or want max settings on a 30inch monitor.

 

[ModestGamer]

why would you buy a 2gb version when you are going to be limited to only 1gb by your other 1gb card anyway?

Pretty sure the ram size of the primary card set the total ram.

 

[toyota]

Pretty sure the ram size of the primary card set the total ram.

nope

 

[bryanW1995]

Pretty sure the ram size of the primary card set the total ram.

100% positive that you are wrong unless amd has some magic "ram-doubling" dust for the 2nd card.

ask apoppin about mix/match xfire.

 

[3DVagabond]

No point at all of buying a 2gig card to go with a 1gig, as others have pointed out. There are uses for 2gig cards though, besides eyefinity and 2560*1600 res and high AA. Not when playing stock games though.

 

[ModestGamer]

100% positive that you are wrong unless amd has some magic "ram-doubling" dust for the 2nd card.

ask apoppin about mix/match xfire.

s I read in the crossfire documents the primary card is the ram the system uses. IE 2gb ram total. if you crossfire you'll get 2gb not 4. but you won't get 1gb.

if you hook a 2gb and 1gb card together you won't get 3gb's either.

unless there is something ambiguos in the documents.

IE 2x 1gb cards it still 1gb

 

[bryanW1995]

I'm not sure what you're trying to say, but let me explain. If you xfire with the 2gb as the primary card and 1gb as the 2nd card, each card will use 1gb. if you flip then, then each card will still use 1gb. when you see 5970 2gb stickers, they are 1gb for each gpu, ie, 2 gb total. If you play a game that is vram limited at, say, 1.3 gb, then you'll still run out of ram unless you use the 2gb card all by itself. I've never personally run into this problem but I've heard of it happening on a few games, expecially with mods installed.

 

[solofly]

What resolution do you play at?

 

[blanketyblank]

I know crossfire can run two cards at different speeds and uses the speed of each card individually, but I haven't seen any reviews of cards using different VRAM size crossfired.
I'd be interested in seeing a 512 and 1GB model tested since few games now use over 1 GB.

 

[Daedalus685]

I know crossfire can run two cards at different speeds and uses the speed of each card individually, but I haven't seen any reviews of cards using different VRAM size crossfired.
I'd be interested in seeing a 512 and 1GB model tested since few games now use over 1 GB.

Crossfire runs asynchronously. While you can run cards at different speeds it does not improve the performance over two of the slower card together.

As far as ram goes. The data in the memory on each card is a duplicate of the other. The total RAM available to a program is always exactly equal to the lowest value on any one card.

As such, a 4890 1gig + 4870 512mb performs identical to crossfire 4870 512s. Similarly, a 5850 + 5870 performs akin to two 5850s. There is of course variation to this, and any game that defaults to a single card will take full advantage of the extra stuff in a primary card (the reason you want the best card primary).

It would make sense that "microstutter" would be worse if one card were drastically faster than another though I'm not sure exactly how the frames are timed.

 

[ModestGamer]

I'm not sure what you're trying to say, but let me explain. If you xfire with the 2gb as the primary card and 1gb as the 2nd card, each card will use 1gb. if you flip then, then each card will still use 1gb. when you see 5970 2gb stickers, they are 1gb for each gpu, ie, 2 gb total. If you play a game that is vram limited at, say, 1.3 gb, then you'll still run out of ram unless you use the 2gb card all by itself. I've never personally run into this problem but I've heard of it happening on a few games, expecially with mods installed.

Thats not the way the documents read. IIRC "big if here" the primary card has most if not all of the ram. It can use 2gb. the secondary card is treated as a additional host but does not make use of ram of AA etc ergo pushing the data back to the primary card. so your limit is still 2gb even with a 1gb and a 2gb card in the system together.

If I read it right and I didn't read it recently. I also think this is a new thing starting with the 5xxx series cards the old 4xxx series cards were in fact different in regards to ram usage in crossfire.

I tried to find the documents outlining this but they seem to be missing or I forgot where they were. I could be wrong. they might limit total memory to the maximum avaialble on the slave card. but that makes no sense beucase the slave card is only really used for rendering calculations.

 

[blanketyblank]

Crossfire runs asynchronously. While you can run cards at different speeds it does not improve the performance over two of the slower card together.

As far as ram goes. The data in the memory on each card is a duplicate of the other. The total RAM available to a program is always exactly equal to the lowest value on any one card.

As such, a 4890 1gig + 4870 512mb performs identical to crossfire 4870 512s. Similarly, a 5850 + 5870 performs akin to two 5850s. There is of course variation to this, and any game that defaults to a single card will take full advantage of the extra stuff in a primary card (the reason you want the best card primary).

It would make sense that "microstutter" would be worse if one card were drastically faster than another though I'm not sure exactly how the frames are timed.

Benchmarks seem to prove you wrong at least in regards to the 57xx series. I'm not sure if what you said was applicable to the 4xxx cards, but a 5770 + 5750 will generally be faster than a 5750 + 5750.

Here's one of the benchmarks I'm referring to:
http://www.xbitlabs.com/articles/video/display/asus_eah5770-powercolor_pcs_hd5750_8.html#sect1

That being said I still don't know what would happen with cards with differing memory sizes.

 

[Daedalus685]

Benchmarks seem to prove you wrong at least in regards to the 57xx series. I'm not sure if what you said was applicable to the 4xxx cards, but a 5770 + 5750 will generally be faster than a 5750 + 5750.

Here's one of the benchmarks I'm referring to:
http://www.xbitlabs.com/articles/video/display/asus_eah5770-powercolor_pcs_hd5750_8.html#sect1

That being said I still don't know what would happen with cards with differing memory sizes.

I had forgotten about that link. You are correct, improved asynchronism was added in the 5000 series. Though many reviews show varyingly good results.

In theory crossfire should have always worked the way it does in that link. This was not the case for the 4000 or 3000 series for various reasons (I believe it has more to do with drivers than hardware as the system for crossfire remains the same). I'll ahve to hunt through the deriver notes.. I can't recall if this was an addition to the drivers or the 5000 series itself.

At any rate.. the memory system is different. They each need a clone of the frame buffer and the texture cache as the pcie bus is not fast enough to communicate these large files from one cards memory to the other for real time use.