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4870 & 4890 in Crossfire..

Vakas

Vakas

Vakas

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If I use both these cards in my system will the speed on the 4890 drop to the samw speed of the 4870?
 
Even though the internet is a great place to find a ton of information, some of it isn’t always accurate and while some claim to have seen performance increases of mixed Crossfire over a pair of HD4850 cards, it wasn’t meant to happen. While performance was marginally better (and we are talking about a difference which was well within the usual margin of error when benchmarking) than a pair of HD4850 cards in Crossfire, we really wonder what the use of mixed Crossfire is.

The problem with this type of configuration is the fact that the faster of the two cards will always downclock to keep pace with the slower card. This means that the core speed of 750Mhz and blistering memory speed of 3.6Ghz on a HD4870 means absolutely squat when paired up with a HD4850 running at 625Mhz / 1.986Ghz. We have a screenshot below to accurately illustrate what is happening as we looped a 3DMark 06 Batch Size test which should theoretically load both cards at 100%.
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http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/9159-ati-hd4870-hd4850-crossfire-performance-review.html
 
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LoadsaMoney said:
Yes it will.
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Its a same im finding it hard to find the ATI official link that had the info about that very thing, they have changed their site allot over time.
Unless things have changed for the 4XXX line has i have had mixed pre OC cards 3870 in my rig.

1 HIS 3870 running pre OC at 840 & 2 sapphire 3870 toxic pre OC at 800 & they all held there individual clocks.
But maybe its a XX70-XX50 thing that does it.
 
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I can clock the gpu and memory speeds for each core of my X2 to different values and it works happily enough. I always thought it was only SLi that demanded each chip had to run at the exact same speed.
 
Speedy Pete said:
so we still dont know? lol
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Put it this way. Why would the ATI overdrive allow you to clock the GPUs/MEM individually if they always had to run at the same speed.

Even the Auto tune will settle on different clocks.

The rules maybe different for mixed versions of the same series.
 
similar to how cards take over different percentages of the screen depending on the ratio of power needed to different sections of the screen at that given time i thought the more powerfull card would take over more of the screen most of the time.

Crossfire is set up to run that way so i cant see why it would downclock like SLI
 
lozzick said:
similar to how cards take over different percentages of the screen depending on the ratio of power needed to different sections of the screen at that given time i thought the more powerfull card would take over more of the screen most of the time.

Crossfire is set up to run that way so i cant see why it would downclock like SLI
Click to expand...

CF is now AFR Alternate Frame rendering, standard now for all games.

With the much older drivers & older cards you could persuade some games to use another render depending on the CCC 3D A.I setting.

Q4 would use Scissors which your on about or AFR.
TMS would only use Chequered render no matter the setting & only lose performance if not on standard.
 
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