Two Sapphire 7970 6GB Vapor-X Vs. One Sapphire 7990 6GB Vs. Two Sapphire 7990 6GB

krokosmile · Oct 18, 2014

I currently have one Sapphire 7970 6GB Vapor-X and one Sapphire 7990 6GB. I wanted to see what would be a better choice - 1. Getting another Sapphire 7970 6GB Vapor-X, or 2. Getting another Sapphire 7990 6GB.

I understand that two 7990's is equal quad-fire of 7970's, which means 1,536 bit of memory bus width, but only 3GB per GPU and total. I was also looking at the fact that cross-fired Sapphire 7970 6GB Vapor-X would have 6GB per GPU, but then of course you only get 768 bit of memory bus width. So, help me see what is more important here - having 6GB per GPU as in two Vapor-X's, or having more bus width as in two 7990s.

Also, I am running three monitors @ 1080.

The way I see the performace rating is as follows:
Two 7990s > Two 7970 6GB Vapor-X's > One 7990

I do not think I am looking at all aspects and wanted to hear what the community thinks.

zeyuanfu · Oct 19, 2014

I would say sell your 7970 and get a new 7990 ad it'll perform better.

krokosmile · Oct 19, 2014

zeyuanfu :

Thanks for the reply. Do, you consider increase in bus from 768 to 1536 bit more important than increase in VRAM from 3GB to 6GB but at 768 bit? Ho w big of a difference in gaming performance in both cases?

zeyuanfu · Oct 19, 2014

You will NEVER need 6 GB of VRAM anywhere except if you're running three instances of Watch_Dogs.

krokosmile · Oct 19, 2014

zeyuanfu :

Well, I am not sure about that. It seems that games will start popping up where you would benefit from 6 GB i.e. Shadow of Mordor, which at this point is debatable but I think it is coming. That is why I was trying to see if there was something that may be I was not considering besides VRAM Vs. memory bus width.

zeyuanfu · Oct 20, 2014

Take a look:
http://linustechtips.com/main/topic/44197-memory-bus-size-and-how-it-effects-your-vram-usage/
http://hardforum.com/showthread.php?t=1673311
http://www.tomshardware.com/forum/363644-33-vram-memory-width

krokosmile · Oct 21, 2014

zeyuanfu :

zeyuanfu, thank you for providing these links. They were very helpful. I did decide to go with the second 7970 6GB as a result as I think it will be more fit for my needs.

Is there a way I can give you kudos? I do not see any button where I could do that - this post was set up as a discussion only. So, I am not sure how to do it.

zeyuanfu · Oct 22, 2014

No, it's okay. I do stuff like this every day (or almost). If you want to thank someone for helping you out, though, make sure to create a forum question and not a discussion

You should be able to get at least 300-500$ for the 7990 as it's a dual-GPU card.

krokosmile · Oct 22, 2014

zeyuanfu :

Great! Thank you.

17seconds · Oct 22, 2014

You already have your upgrade in hand... 7990 + 7970 Trifire.
http://www.tweaktown.com/articles/5414/amd-radeon-hd-7990-6gb-and-hd-7970-ghz-edition-video-cards-in-crossfirex/index.html

(Also fixed the thread to a Question so you can select a Best Answer.)

krokosmile · Oct 22, 2014

17seconds :

Yes, I know, but I wanted to effectively increase usable VRAM. Having tri-fire with existing cards would only allow me to use 3GB as VRAM does not stack up. On the other hand if I have crossfire and may be later tri-fire of 7970 6GB, then I would be able to do just that.

Thank you for updating this thread to a Question.

17seconds · Oct 22, 2014

krokosmile :

I'm not sure I'm following you. Each of those GPUs, regardless, is only going to have 3GB of VRAM available no matter what. As you said it doesn't stack, Crossfire, Trifire, or single.

krokosmile · Oct 22, 2014

17seconds :

krokosmile :

I'm not sure I'm following you. Each of those GPUs, regardless, is only going to have 3GB of VRAM available no matter what. As you said it doesn't stack, Crossfire, Trifire, or single.

I meant cross-firing two 7970 6GB cards. And may be in the future having three of these cards. In which case I would sell 7990.

17seconds · Oct 22, 2014

Got ya. Didn't know they made 6 GB 7970s.

anbello262 · Oct 22, 2014

I don't think that memory and memory bandwith are that important... GPU cores are a lot more important for performance.

krokosmile · Oct 22, 2014

anbello262 :

They are all important. Take a look at links posted by zeyuanfu. These get explained pretty well.

anbello262 · Oct 22, 2014

I know they are all important, I'm sorry, I didn't explain myself properly.
I meant to say that, between having 2 GPUs and 4 GPUs, even with half the memory, the 4 GPUs would be way better.
That assuming vram is enough. And I believe that, for today's standars, 3gb is enough.

zeyuanfu · Oct 23, 2014

Actually, having four GPUs won't give you a very big improvement. Take SLI, for example. If you have one GPU, it gets used 100%, if you have two, the second one only gets used about 75% and it does down and down.

krokosmile · Oct 23, 2014

anbello262 :

I am personally a bit biased towards Vapor-X products. I like the way these cards run - very cool and very quite comparing to 7990, which is not that loud but does have a specific noise and is also hotter. So I was evaluating few aspects and two of them being VRAM and bus width. I think 7970 quadfire (or two 7990) with 3GB total is just unnecessary and "unused" GPU power relative to the amount of VRAM. That is why I opted out to have two 7970 6 GB Vapor-X cards, and may be later (way in the future) I will get a 3rd one to have more GPU power.
Here is something interesting - the new Titan Z has 12 GB VRAM and two GPUs that add up to 768 bit - these two specs are equal two cross-fired 7970 6 GB Vapor-X cards. I am sure there are plenty of differences (so, do not hate on this comment) - of course, price is one of them. Here is a link to amazon for the Titan Z card - http://www.amazon.com/Nvidia-GeForce-900-12080-0000-000-Ultimate-Graphics/dp/B00KVKAOSM/ref=sr_1_6?ie=UTF8&qid=1414113891&sr=8-6&keywords=titan+z

zeyuanfu · Oct 24, 2014

Having 3 cards in CFX won't give you a very large performance increase.
Also, the Titan Z is a ripoff and you can get four-way 980 SLI with that money.

krokosmile · Oct 25, 2014

zeyuanfu :

That is why I am not jumping to get the 3rd card at this point. And agreed on the overpriced aspect of Titan Z.

zeyuanfu · Oct 25, 2014

Actually, the Titan Z just got a price drop to ~1500$, which makes it a tiny bit more appealing

Two Sapphire 7970 6GB Vapor-X Vs. One Sapphire 7990 6GB Vs. Two Sapphire 7990 6GB

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