Gigabyte 7870 Overclockability and Throttling

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Gigabyte 7870 Overclockability and Throttling

Postposted on Wed Oct 03, 2012 1:13 am

So, I thought I would report in. I've been doing some messing around with my 7870, with a tinge of overclocking and have found some disappointing results. I don't know if it specifically relates to Gigabytes card or 7870s in general (I have a GV-R787OC-2GD), but it seems to suffer from a GPU throttling cap. Specifically when the GPU hits 70c it throttles it down 450mhz for about 2 seconds, after which it goes back to the normal clocks and the temperature continues to climb back up.

This is at +20% power.

This is only part of it though. I noticed my VRM temperatures get really hot and decided to pop off my heatsink out of curiosity and to replace the thermal paste. After removing it, I can safely say the card has absolutely no VRM cooling. Nothing makes contact with the VRMs, which would give credit to TRs recent 7870 overclocking results. It appears the after market cooler has no VRM cooling and from the design of the card, it would be extremely hard for the heatsink to actually make contact with the VRMs (they're buried lower and next to capacitors which have about double their height).

After replacing the thermal paste, I can keep the GPU temperature relatively stead under 100% fan load, but the VRMs quickly rise to +110c at which point I don't feel comfortable continuing the test to see how hot they can get before the card locks up. It appears as though there is no thermal throttling in place to protect the VRMs from heat damage. Keep in mind the VRMs never reach these temperatures normally, only when running OCCT which seems to do the best at making the card suck more juice.

This sort of puts a damper on the overclockability of the card. I have to keep it under 70c and I can't draw more then 14.5~ amps through it on VDDC in without the VRMs overheating regardless of how cool the GPU. I'm not entirely sure why there is 70c throttle on the card either.

I've done a couple things to get around this as the VRM temps prevent me from completely stress testing the card. It appears as though the GPU is fine with extra voltage and higher clocks, it just makes the VRMs overheat exponentially faster (this also coincides with why the cards crashed so easily when TR overclocked them). Quite literally I bumped the voltage by .04 and it lasted about a minute at 100% fan speed before the VRMs once again became too hot even though it seemed perfectly stable.

Now if I turn down my power limit to like 10% it allows the card to stay cooler, but this also limits my FPS in OCCT to less then what the GPU overclock gives me. So it's really a net loss even though the GPU is running faster. Really it seems like 14.6a is the point at which the VRMs no longer stay cool enough. Getting there through any combination of GPU speed, power limit setting, or core voltage.

Ideally I could run my card at +20% and higher clocks in games as they don't fully utilize the whole card (GW2 for instance only draws +6a on my VDDC in at my normal clocks under 100% load),but I still have no way of stress testing my card without the VRMs overheating to see what is actually stable.

Point of all of this. Third party coolers, at least for this specific Gigabyte model and the ones TR tested blow donkey nuts and don't cool VRMs properly. The 7870 may have a imposed thermal limit of 70c either in drivers or in hardware, I'm not sure which. There are only a handful of posts on the internet that reference this limitation, bit it very much exists. One post I read stated that reverting to 12.6 drivers fixes the 70c thermal cap. I'm not sure if this is or isn't intentional by AMD, there aren't enough people noticing it to generate buzz.

My guess is the 7870 is too good at OCing for its own good and it's nipping at the higher end cards. For instance my card is clocked at 1100Mhz, but easily hit 1150 without any voltage tweaking and hit 1200 with that small bump in voltage, but resulted in VRM overheating (I didn't try going higher then that because it wasn't worth it due to the VRMs). Oh and the memory hit 1450mhz (limitation of CCC) without throwing any sort of fuss. That I could stress test as for some reason it added absolutely no heat to the card... or at least very little compared to the GPU. The memory did have thermal pads on them that connected them to the heatsink.

A little more on the heatsink testing. I originally had a 6970 this card replaced with a traditional blower. From messing around with the fan speed settings on this card, I can safely say subjectively that it isn't all that great at dissipating heat. The heatsink may be good, but it has no where to blow the heat so it quickly becomes saturated (the heat is also blown into the card and doesn't have good direction). The difference in heat dissipation at 20%, 50%, and 100% is marginal even though the CFM drastically increases between those settings. Testing my 6970 on the other hand produced extremely good and also loud results when changing the fan speed settings manually, even keeping the GPU bottomed out at around 40c when testing the overclocking capabilities of that card. They both used the same thermal paste.

I understand that it's two different cards, but there really is something wrong when increasing fan speed doesn't have a noticeably direct impact on heat dissipation. I want to say case blowers like these truly ARE inferior (this has nothing to do with VRMs). Even if you had a box fan hooked up to the side of the case they still aren't good at putting the CFM through the fins efficiently. It may be a giant block of metal, it may have more heatpipes, and it may have more spinners, but it's overall quite a bit less efficient, not to mention the heat it dumps in your case.

Buy a card that blows outside, not in the case. I would've if I had a choice.

Some final notes. This card has a thin plastic shroud that it uses for the fans and they have thin blades. It produces a noticeable whine/rattle and appears as though the fans are of very low quality.

http://www.newegg.com/Product/Product.a ... 6814125418
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Wed Oct 03, 2012 1:40 am

Quick update: It appears that when CCC resets due to the graphics driver hanging (bad clocks), the 70c GPU limitation is removed. This still doesn't stop my VRMs from self-immolating, but seems to be a pretty good sign that this is being done by the drivers. I'm still not sure if it's intentional or a bug, but it doesn't seem to reinitialize after the drivers come back online.

Update2: It appears that the 70c thermal throttle is completely gone now. I've done multiple tests over the last two weeks and this is the first time I've seen it disappear, it's also the first night I've used Afterburner to change my voltage. I'm no longer able to reproduce the 70c thermal throttle, even though it happened every time leading up to this posting.

This doesn't change the fact that I'm soft capped due to not having VRM cooling though. My guess is Afterburner tweaked something in the driver settings when I did the overvolt. I will have to report back here after the next catalyst driver release.
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Wed Oct 03, 2012 3:01 am

Bensam123 wrote:Quick update: It appears that when CCC resets due to the graphics driver hanging (bad clocks), the 70c GPU limitation is removed. This still doesn't stop my VRMs from self-immolating, but seems to be a pretty good sign that this is being done by the drivers. I'm still not sure if it's intentional or a bug, but it doesn't seem to reinitialize after the drivers come back online.

Update2: It appears that the 70c thermal throttle is completely gone now. I've done multiple tests over the last two weeks and this is the first time I've seen it disappear, it's also the first night I've used Afterburner to change my voltage. I'm no longer able to reproduce the 70c thermal throttle, even though it happened every time leading up to this posting.

This doesn't change the fact that I'm soft capped due to not having VRM cooling though. My guess is Afterburner tweaked something in the driver settings when I did the overvolt. I will have to report back here after the next catalyst driver release.



When did you buy the card? Can you still return it? It seems to me that the best way to cool a video card is to buy the stock standard version and use an aftermarket cooler that covers every bit of the card. The caveat is that aftermarket coolers are quite expensive and for the total cost you could have bought a higher end model but ofc with stock cooling as well.

Reading the user reviews on newegg for the HD 7870 equipped with custom coolers i'm not certain there is a particular model that can be trusted and recommended over another.
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Wed Oct 03, 2012 9:59 pm

No, unfortunately I can't. This was a RMA from a Gigabyte 6970 that died. All of their 7XXX series have the same stupid cooler on it. I thought about ebaying it and buying a different model, but I really don't want to eat the loss for the difference between the two.

In my experience most people don't actually check to see if the VRMs are being cooled properly, even though it's a integral part of both the longevity and overclockability of the card in general. All the after market coolers I've looked at only cover the GPU, you have to purchase VRM heatsinks (or they come with them), which you then have to attach to the VRMs. Most people when talking about how cool their card is are only mentioning GPU temps and usually not under saturated conditions (like running furmark for 5 minutes and calling it good while the side of their case is off).

Most third party coolers don't cover the memory either(!), which is most definitely important if you plan to overclock memory. It's actually quite hard to make a aftermarket heatsink for cards now unless they clone the reference card to the letter. They either have to be custom tailored for that specific model from that company or they only cover the GPU, which leaves all the other components exposed. Like just shopping around on Newegg you can't tell what the heatsinks are actually covering (looking at the cards) and people don't mention it in reviews. They just go 'omgs my GPU temps are now 5c cooler!'. This is also why there is such a sparse selection of GPU coolers, because each one needs to be custom tailored for boards now unless they follow the reference design... but they still don't cover the VRMs and usually memory.

This is why I generally also stay with reference video cards even if it means spending a extra $10-20. In my experience AMD (probably Nvidia too) always cover the important parts with their coolers (in addition to blowing air outside the case). My 6970, which was a identical match to a reference 6970, had the memory covered, and the heatsink actually covered the VRMs as well with TIMs in between them. I used to buy aftermarket coolers for my GPU, but stopped doing that once I realized that VRMs now need cooling too. It's better to just stick with the reference cooler then buying a third party one, unless you use water cooling, which is a completely different ball game.

I do, however, replace any thermal paste on whatever heatsink they send me with Arctic Silver... I've found that usually drops temps by about 5-8c and increases thermal transfer (think that's right), so the card doesn't heat up as fast.
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Wed Oct 03, 2012 10:26 pm

That's mostly why I've leaned Nvidia this last couple of rounds (since the GTX200's)- I want a stock blower that cools everything and gets rid of the hotter air, and Nvidia's blowers have usually been better. I really don't overclock my GPUs that much though; I'd rather them stay quiet.
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Thu Oct 04, 2012 12:17 am

Even if you do OC I found the reference blowers to be quite good. After market coolers are theoretically quite good at dissipating heat in terms of material, number of fins, heatpipes, and even CFM, but they usually don't have good flow or design. It's all paper that doesn't translate to the real world... Like reference coolers blow the air directly across fins and out the outside of the case. I've found heat dissipation with a reference cooler to actually be better. I would buy a reference cooler for this specific video card if it had one, but when I popped off the heatsink the board is rearranged in such a fashion where a reference cooler no longer works.

I can't comment about Nvidia reference coolers cause I've never owned one or had experience with one, but I'm sure they're in a similar ballpark. I'm sure theirs also cover the VRMs.

Oh and it doesn't come with two DVI ports, which pissed me off... but thats not on topic.
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Mon Oct 15, 2012 11:05 am

I was just skimming, but can you shave some VGA heatsinks down and fit them underneath the existing cooler? Sometimes, if you want it done right, you've got to do it yourself.
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Wed Apr 10, 2013 5:35 pm

I know this is necro but trying to pm OP was met with error this user does not exist.
So i saw your post about the 7870, i have the same model and tried overclocking, i overclocked my memory clock to 1250 stable but look at my VRM temperatures.... im getting concerned.
http://i.imgur.com/AEWUgRz.gif
http://i.imgur.com/zcKzZhc.gif

Please help you are the only post i found on the internet about this :( .
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Thu Apr 11, 2013 12:23 pm

Those two shots were taken at the same time? GPU temps, fan speed, clock, all the same. The only difference is the reported VRM temps. Are they sporadically jumping around? If so, I don't think GPUz is reporting the VRM temps properly.
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Re: Gigabyte 7870 Overclockability and Throttling

Postposted on Thu Apr 11, 2013 1:53 pm

The shots were taken after i finished playing games that night mostly bf3.
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