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R680: AMD ATI Radeon HD 3870 X2

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bustamove 31st January 2008, 19:43 Quote
I think I follow that Tim, but I dont understand why ati would make a 1gb card if it only uses 512mb?

are you saying that single card crossfire only uses 512mb as well as the x2 version?
You can probably tell that Im not very technically literate. but I dont understand why it performs on a par or better in most tests Ive seen that 2 single cards in cf mode?
thats the part im getting lost at.
Prior to buying the card, I did consider buying two singles but the possibilty of having two x2's in crossfire in the future clinched the choice I made.
thanks for your reply to the question.
Tim S 31st January 2008, 20:45 Quote
It's only a 512MB GPU because it's two GPUs and each GPU has its own pool of memory. Everyone still refers to it as a 1GB or 2x512MB GPU though.

When the CPU sends commands (from the game) to the graphics card, it is sent to both cards in a CrossFire/SLI configuration - this data is stored in both memory pool as one GPU can't access the other's memory pool directly (there's no physical connection).

The reason the X2 might perform slightly better in some situations is because of the higher core clock. There is a 50MHz increase on the core (825MHz vs 775MHz), but the memory loses 450MHz (effective, 1800MHz vs 2250MHz)... In memory bandwidth limited scenarios, the memory clock is the reason why the 3870 X2 can be slower than the 3870 CrossFire config.

Hope this helps to explain it a bit more. ;)
Tyinsar 31st January 2008, 22:33 Quote
Quote:
Originally Posted by Tim S
I'm sure I mentioned it in the text (sorry if I didn't, must've cut it out in a final edit)... but multi-monitor works fine in both 2D and 3D. It's much more transparent than the 7950 GX2 in that respect.
Perhaps I missed it - but, since I still can't see it, my question remains.

In 3D mode does the system:
1) see it as a single GPU,
2) while using the power of both,
3) AND powering 2 monitors?

If yes then it's a Huge step up from the 7950 GX2. That might would also mean that (span / stretch mode is possible - in XP at least - in my perfect imaginary world I could do this on 64bit Vista but it looks like that isn't, & won't be, possible.)
Quote:
Originally Posted by bustamove
...@ Tyinsar, im going to hook it up to my 24" monitor in the morning, my rig is watercooled and its a bit of a pain moving the pc around.
not sure about the stretch thing but ill check it out....
Thank you very much. I look forward to hearing your results.
bustamove 1st February 2008, 10:02 Quote
Quote:
Originally Posted by Tim S
It's only a 512MB GPU because it's two GPUs and each GPU has its own pool of memory. Everyone still refers to it as a 1GB or 2x512MB GPU though.

When the CPU sends commands (from the game) to the graphics card, it is sent to both cards in a CrossFire/SLI configuration - this data is stored in both memory pool as one GPU can't access the other's memory pool directly (there's no physical connection).

The reason the X2 might perform slightly better in some situations is because of the higher core clock. There is a 50MHz increase on the core (825MHz vs 775MHz), but the memory loses 450MHz (effective, 1800MHz vs 2250MHz)... In memory bandwidth limited scenarios, the memory clock is the reason why the 3870 X2 can be slower than the 3870 CrossFire config.

Hope this helps to explain it a bit more. ;)

Thanks again Tim that explanation was clear enough for my limited technical brain.

Tyinsar, I will try what you suggest later today and see what gives on that.;)
naokaji 1st February 2008, 10:08 Quote
Quote:
Originally Posted by Tyinsar
Perhaps I missed it - but, since I still can't see it, my question remains.
3) AND powering 2 monitors?

previously with both sli and crossfire multimonitor was a no go (except if you added a card that was not part of the sli / xfire config).
but, ati finally decided to allow multi monitor with crossfire, nvidia will surely follow shortly with allowing multimonitor + sli.
Tim S 1st February 2008, 10:20 Quote
Quote:
Originally Posted by Tyinsar
Perhaps I missed it - but, since I still can't see it, my question remains.

In 3D mode does the system:
1) see it as a single GPU,
2) while using the power of both,
3) AND powering 2 monitors?

If yes then it's a Huge step up from the 7950 GX2. That might would also mean that (span / stretch mode is possible - in XP at least - in my perfect imaginary world I could do this on 64bit Vista but it looks like that isn't, & won't be, possible.)

It's seen as two GPUs in GPU-monitoring software like GPU-Z for example, but the driver sees it as one card - there is no need to enable CrossFire, but in games that have a multi-GPU optimisation switch, you need to enable it (I'm thinking Call of Duty series here). You can also power two monitors without having to go into display properties/driver CP to enable the second display when you're not in 3D.

You're right though, at least in terms of transparency, it is a massive step forwards over the 7950 GX2. It's still inherently limited in the same way that the 7950 GX2 was though (driver support - a MASSIVE problem with the 7950 GX2/Vista... but I don't need to go back to that one again).
Tyinsar 1st February 2008, 16:15 Quote
Quote:
Originally Posted by naokaji
previously with both sli and crossfire multimonitor was a no go (except if you added a card that was not part of the sli / xfire config).
but, ati finally decided to allow multi monitor with crossfire, nvidia will surely follow shortly with allowing multimonitor + sli.
That is indeed good news. ;) to you & to ATI.
Quote:
Originally Posted by Tim S
It's seen as two GPUs in GPU-monitoring software like GPU-Z for example, but the driver sees it as one card - there is no need to enable CrossFire, but in games that have a multi-GPU optimisation switch, you need to enable it (I'm thinking Call of Duty series here). You can also power two monitors without having to go into display properties/driver CP to enable the second display when you're not in 3D.

You're right though, at least in terms of transparency, it is a massive step forwards over the 7950 GX2. It's still inherently limited in the same way that the 7950 GX2 was though (driver support - a MASSIVE problem with the 7950 GX2/Vista... but I don't need to go back to that one again).
My concern is that my setup (as seen in my avatar) requires span or stretch mode. After buying two 8800 GT cards I found out that span mode only works if the monitors are on the same GPU.:( I've been contemplating all kinds of crazy setups to make this work better but, if this card can do it, ATI may have the best & simplest answer for me.
Tim S 21st February 2008, 00:10 Quote
Price cuts ahoy! £235 (inc VAT): http://www.ebuyer.com/product/140437
dmak 25th February 2008, 04:48 Quote
one thing I have been wondering, is there a difference between vista 32bit and 64 bit with this card, or gaming in general? The one reviewer that is giving a generally "not good" for this card is HardOCP, but they are using vista 64, and I was wondering if this makes a difference

also I have noticed a few people have been experiencing one of the cores not working properly
http://forums.guru3d.com/showthread.php?t=253628

Just curious what people think about that problem and vista 64
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