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memory Overclocking on the HD 7950 is this normal ?

Discussion in 'AMD / ATI' started by fwix, Jan 20, 2013.

  1. fwix New Member

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    hey guys

    i have a question about memory frequency

    i have a gig WF3 hd 7950 so I've managed to oc to 1307/1900 max oc bench - 1280/1800 stable gaming , but the thing is about that memory if i oc it from 1250 to 1800 or 1900 I gain only 1-2-3fps in games like metro crysis 2 bf3 - alan wake ultra preset on the average of 50-60 frame is this normal ? i mean we all know that overclocking the memory don't add allot of fps but seriously it's + 125 GB/S bandwidth it's make no sense in all to gain only 1-3 fps , perhaps because the hd 7950 already have enough bandwidth so adding more bandwidth don't help with more speed process !

    ps: in other gpu like gtx 590 gtx 580 gtx 470 hd 5870 hd 5850 hd 6870 hd 4890 hd 5770 ect all of the gpu's that i had when it's come to memory oc I always gain +3-4 fps and it's only +20-40GB/S so I'm not sure about that with this hd 7950 .... (i know gpu's are not the same- different architecture ect but I'm not sure about +120 gb/s to gain 1-3 fps ..)
     
  2. mstenholm

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    I'm not a gamer but my guess is that the high end ATI GPUs are not hampered by memory speed in the first place.

    Edit: Nice OC btw. I'm sitting at 1050 MHz (24/7) with a decent Asus 7950 but never tested it further then that.....
     
    Crunching for Team TPU More than 25k PPD
  3. ruff0r

    ruff0r

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    If i remember correctly the ATI 7xxx series has ECC which means even if your RMA makes wrong results it will calculate it again until it has the right result what also decreases the performance since it has to do it twice....
    Try clocking it down to 1600 which most cards do properly and try raising voltages for your ram
     
  4. cadaveca

    cadaveca My name is Dave

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    Gains are there to be had. But, it plays out a bit strange.

    If you look at 7970 to 7950 design difference, there's a very exact correlation between the increases in clock speed, shader amount, and ram speed. Clearly there is an "optimal" ratio for the architecture between those, and even the driver is going to be designed around those ratios.

    Going from 1250 to 1650 gets me a couple hundred points in 3DMark11. Not a lot.

    With a core speed of 1050:


    1250:

    http://www.3dmark.com/3dm11/5641056

    Score:9583

    1650:

    http://www.3dmark.com/3dm11/5641087

    Score:9791

    A difference of 208

    Then, in the middle, 1450:

    http://www.3dmark.com/3dm11/5641138

    Score:9655

    136 points from 1650, 72 from 1250.




    Now, with a core speed of 800.

    1250:

    http://www.3dmark.com/3dm11/5641206

    Score:7830

    1650:

    http://www.3dmark.com/3dm11/5641269

    Score:7958

    A difference of 128

    Then, 1450:

    http://www.3dmark.com/3dm11/5641236

    Score:7877

    81 points from 1650, 47 from 1250.


    Notice nearly the exact same ratio.
     
  5. fwix New Member

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    ecc are on the series hd 5xxx/6xxx either :)

    emmmm yeah it's so strange this story of the memory on the hd 7950 !! so there is no technical info to explain this ?
     
  6. Steevo

    Steevo

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    http://en.wikipedia.org/wiki/GDDR5
     
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  7. DarkOCean

    DarkOCean

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    @OP That's because 79xx series already have sh!tloads of bandwidth ,more than needed really (just look at 7870 1536sp wich has only 192gb/s and its @3 % diff. from the 7950 in speed)... so that's why you wont see any significal improvement by giving those gpus even more bandwidth ;They literally bathing in it.
     
    Last edited: Jan 21, 2013
  8. The Von Matrices

    The Von Matrices

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    Yeah, even with a 6MP resolution I see no significant performance improvement going from the stock 1375 MHz to 1750 MHz on the memory. The 7900 series just isn't memory bandwidth constrained.
     
    Last edited: Jan 21, 2013
  9. fwix New Member

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    emmmmm that's what I thought ! even using crysis 2 maldoh 4 mod + 2.400 GB vram load it's only +3 fps so what i think is that the 384 bus/240gb/s-288gb/s are enough to hold what the tahiti need and honestly this is the first time that i bought a gpu that have more than 190 gb/s BW , in the past it was limited to 230 gb/s oc or so but anyway thx guys :) i ll do more bench lowering the memory and the gpu then max out the gpu then lowering memory ect to see how the ratio gpu/memory sound's like on gaming lik crysis metro + using some AA -msaa8x-16x to max out the bandwith :D
     
  10. fwix New Member

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    euuuh i guess we all wrong on this

    this is a bench that i just did :

    hd 7950
    resident evil 5 bench 1080p max out + filter edge detect + supersampling

    default 900/1250 = 61 fps

    memory:
    mem oc 900/1800 = 71 fps +10 fps gain
    mem downclock 900/800 = 48 fps -13 FPS loss

    gpu:
    gpu oc 1280/1250 = 66 fps +5fps gain
    gpu downclock 700/1250 = 56 fps -5 fps loss

    mem+gpu oc 1280/1800 = 78 fps +17 gain
    mem+gpu downclock 700/800 = 45.7 -15.3 fps loss

    ratio oc gain +100%gpu+50%mem = 2G:1M

    so definitely it's not useless to oc the memory it's just depend on the engine of the game as i see here R.E5 is bandwidth demanding game so the impact of oc is plus when oc the memory !!!

    can anyone confirm what i just did by testing him self this game because i just don't get it gpu oc is so useless + 380 mhz for 5 fps + 100w consumption ...

    ps: I'm still working on another games to close out this subject
     
    Last edited: Jan 21, 2013
  11. SonDa5

    SonDa5

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    I concur. I have seen the performance results in benchmark over clocking.


    I think the key here is that in order for the bandwidth to fully be appreciated the GPU core and cpu/system all have to be over clocked.
     

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