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2 GPU cards, different VRAM stats

marblemarble Posts: 7,500
in The Commons

Here's something that surprised me. I have just installed a second GPU so that now I have a GTX 970 and a new 1070. I loaded George (and his hair) into a new scene and ran GPU-Z to see how much VRAM he uses. The odd thing is that he uses a LOT more of the 1070 VRAM than the 970. I do have the display connected to the 1070 so that would account for some but without anything loaded it reports about 350MB which is negligeable. Here are the stats.

 

Comments

  • TooncesToonces Posts: 919

    Yes, my 2 cards exhibit the same behavior, tho they're usually 500 MB different, not quite as big of a difference as what you're seeing.

    Plus one shows (Dedicated) while the other doesn't and they're the same type of card.

    Not a big deal to me. I just use GPUZ as a rough estimate...primarily just to ensure that the cards are actually being utilized. I assume there is mysterious mojo at work which accounts for the differences, likely related to OS, display, etc.

    Would be good if someone knew the answer though, as it is a curiosity.

  • marblemarble Posts: 7,500

    Actually, it is quite a pleasant surprise in one way: if the 1070 VRAM usage is roughly accurate then the same amount on the 970 would push it over the 4GB limit. So it means I can use both cards for more of my scenes. Of course, as you say, it may not be accurate but I do remember that when I only had the 970, it was pretty good at letting me know when I was getting close to that limit.

  • twitch99twitch99 Posts: 81
    marble said:

    Actually, it is quite a pleasant surprise in one way: if the 1070 VRAM usage is roughly accurate then the same amount on the 970 would push it over the 4GB limit. So it means I can use both cards for more of my scenes. Of course, as you say, it may not be accurate but I do remember that when I only had the 970, it was pretty good at letting me know when I was getting close to that limit.

    Do you have OptiX Acceleration on or off?   I find that effects how VRAM is shared across two GPU, I have a GTX 970 and GTX 1080

  • marblemarble Posts: 7,500
    twitch99 said:
    marble said:

    Actually, it is quite a pleasant surprise in one way: if the 1070 VRAM usage is roughly accurate then the same amount on the 970 would push it over the 4GB limit. So it means I can use both cards for more of my scenes. Of course, as you say, it may not be accurate but I do remember that when I only had the 970, it was pretty good at letting me know when I was getting close to that limit.

    Do you have OptiX Acceleration on or off?   I find that effects how VRAM is shared across two GPU, I have a GTX 970 and GTX 1080

    I just checked - Optix is (and was) off. 

  • outrider42outrider42 Posts: 3,679

    This is why I'd use the larger card to run the screen, like you have. Because it allows the smaller card to spare every bit of its capacity for rendering so it can stay in play more often. So while that might shave a tiny bit off the top card, imo, having both cards available more often is much greater benefit.

    BTW, how's the combo working out? The 1070 is the card I'm most interested in. Since you have a 970 and 1070, are your seeing a big boost from having both? That's essentially the combo I'm hoping to have one day.

  • marblemarble Posts: 7,500
    outrider42 said:

    This is why I'd use the larger card to run the screen, like you have. Because it allows the smaller card to spare every bit of its capacity for rendering so it can stay in play more often. So while that might shave a tiny bit off the top card, imo, having both cards available more often is much greater benefit.

    BTW, how's the combo working out? The 1070 is the card I'm most interested in. Since you have a 970 and 1070, are your seeing a big boost from having both? That's essentially the combo I'm hoping to have one day.

    I wish I could tell you but I have not yet had chance to render a full scene yet. A G3F with a Ghostlight and Painters Lights but no props, no clothes, no hair, rendered (approx 1200 x 900) in under 40 secs but I'll only find out when I put tigether a working scene. My PC has been shipped to my new home in New Zealand so I am now catching up, remembering things I forgot about and trying new products I've been buying in the meantime.

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