CF with 512mb and 2gb cards - result?

Hey. I've paired a 4GB 4870X2 with a 512mb 4870 card at lower clock speed - what impact on performance does the lack of frame buffer have?
Currently I'm scoring about 25.5K in 3dmark06 with my cpu @ 3.8Ghz with 8 threads and memory at ddr3-1448 7-7-7-20 and the 3 cards in CrossFireX mode.
This is with msn and kaspersky active after a reboot.
Somehow I find this figure a bit low, as I got 13.7K with the old 512mb card alone. Is 25K what I should expect?
Does it make any difference if I have the 4870 or the x2 in the first pcie slot? (both run x16)


ps. in reallife it runs everything I throw at it @ 60fps vsync'ed - but curiously still lags in video playback in cod mw2 (before it would run at 60fps and sometimes drop to 1 - appearently when loading from the harddrive while the level is active).

I can now play dragon age at max settings though on my 22" even with the improved texture pack addon enabled. Marvelous. Makes a great game even better.

NFS Shift still suffers from severe input lag though even in 1024 resolution - but fps wise runs fluidly both with 1 and 3 gpu's.
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  1. I didn't even know you could get a 4GB 4870x2. I believe because you've crossfired it with a 512mb 4870 all you'll get is 512MB. Not 4GB or 4GB+512MB.
    Also if one card has lower clocks than the other. the faster card will downclock itself to the speed of the slower card.

    You are being slighly bottlenecked in 3Dmark06 (Yes, I know how ridiculous that sounds with a 3.8Ghz Core i7)

    I get 26400 with one HD5850 at 920/1125 and a Ci7 920 at 4.4Ghz HT on.

    Don't worry about 3dmark06, what matters is game performance.
  2. Ye I only get to use 512MB frame buffer no matter how much is on the X2 - but what I was wondering is if it makes a difference?
    As for clock speed - I once read it'll clock down to the slowest speed - but if catalyst is to be trusted it doesn't! The X2 still runs faster than the old 512 card even when crossfire is on.
  3. neiroatopelcc said:
    Ye I only get to use 512MB frame buffer no matter how much is on the X2 - but what I was wondering is if it makes a difference?
    As for clock speed - I once read it'll clock down to the slowest speed - but if catalyst is to be trusted it doesn't! The X2 still runs faster than the old 512 card even when crossfire is on.


    I think CCC is telling porkies. You cant have one card rendering a image faster than another card thats also trying to render the same image

    512MB is fine for any resolution under 1920 x 1080, Although I did have a 4870 512MB once and it did fine at that resolution but really struggled if I upped the eyecandy (E.g AA)
  4. A 4870x2 is like having 2x 4870 1gb cards. Crossfire always defaults all participating cards to the lowest settings available. This trifire setup will be essentially the same as 3x 4870 512mb cards. When active, crossfire will downclock the 2 faster cards to the slowest cards specs. You may see different clock speeds while the trifire is not being utilized, but the way CF works, all the cards have to be running exactly the same.
  5. JofaMang said:
    A 4870x2 is like having 2x 4870 1gb cards. Crossfire always defaults all participating cards to the lowest settings available. This trifire setup will be essentially the same as 3x 4870 512mb cards. When active, crossfire will downclock the 2 faster cards to the slowest cards specs. You may see different clock speeds while the trifire is not being utilized, but the way CF works, all the cards have to be running exactly the same.


    That's how I understood the theory as well. But according to CCC this is my hardware as of right now :

    Primary Adapter
    Graphics Card Manufacturer Powered by ATI
    Graphics Chipset ATI Radeon HD 4870 X2
    Device ID 9441
    Vendor 1002

    Subsystem ID 0266
    Subsystem Vendor ID 1043

    Graphics Bus Capability PCI Express 2.0
    Maximum Bus Setting PCI Express 2.0 x16

    BIOS Version 011.007.000.000
    BIOS Part Number 113-B50902-X00
    BIOS Date 2008/08/11

    Memory Size 2814 MB
    Memory Type HyperMemory

    Core Clock in MHz 790 MHz
    Memory Clock in MHz 915 MHz


    Linked Adapter
    Graphics Card Manufacturer Powered by ATI
    Graphics Chipset ATI Radeon HD 4870 X2
    Device ID 9441
    Vendor 1002

    Subsystem ID 0266
    Subsystem Vendor ID 1043

    Graphics Bus Capability PCI Express 2.0
    Maximum Bus Setting PCI Express 2.0 x16

    BIOS Version 011.007.000.000
    BIOS Part Number 113-B50902-X01
    BIOS Date 2008/08/11

    Memory Size 2814 MB
    Memory Type HyperMemory

    Core Clock in MHz 790 MHz
    Memory Clock in MHz 915 MHz


    Linked Adapter
    Graphics Card Manufacturer Built by ATI
    Graphics Chipset ATI Radeon HD 4800 Series
    Device ID 9440
    Vendor 1002

    Subsystem ID 0502
    Subsystem Vendor ID 1002

    Graphics Bus Capability PCI Express 2.0
    Maximum Bus Setting PCI Express 2.0 x16

    BIOS Version 011.003.000.001
    BIOS Part Number 113-B50701-100
    BIOS Date 2008/06/09

    Memory Size 512 MB
    Memory Type GDDR5

    Core Clock in MHz 750 MHz
    Memory Clock in MHz 900 MHz
    Total Memory Bandwidth in GByte/s 115,2 GByte/s


    Notice there's 40Mhz difference in gpu speed and 15mhz in memory.

    ps. sorry - the x2 has 2x 1.4gb memory not 2x2gb - I must've read wrong last time. Anyway, the difference is still huge compared to 512mb
  6. No, your x2 has 2gb total memory (1gb per GPU) but that data includes the windows aperature, the reserved system memory per GPU.

    Those may be readings obtained during inactive crossfire status. You do not have a special mobo or cards, and crossfire WILL always match the cards in use one way or the other. For example, you can crossfire a 4870 and a 4850, but the result will technically be the performance of 4850x2. This is a well known factoid.
  7. ^+1

    Anyway, the drivers will assume the smallest amount of RAM the cards have in common, which in this case is 512MB. It will be like having 3 4870s with 512MB. Because of this you may be better off just using the 4870X2 without the 4870 512MB with games and settings that make use of more than 512MB of RAM.
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