7970 vs 7950 vs 2x6950 for BITCOIN mining?

[thilanliyan]

So I am trying to decide whether I should sell my 2 6950s and go with a single 7970 or 7950. The main purpose is for bitcoin mining with gaming being secondary since I just don't have the time like I used to.

Currently my 2x6950s pull in about 650MH/s while undervolted at about 300w total system power (from Kill-a-Watt). Power consumption is not that much of a concern since I pay a fixed amount for utilities where I am at right now. The card would be watercooled.

Any suggestions?

 

[Binky]

If my memory is correct, the overclocked 7950 should do about the same mh/s while using less electricity. Isn't the $330-$350 cost about the same as you might get for the used 6950's? It sounds like a side-grade rather than an upgrade.

 

[SlowSpyder]

I'll check when I get home. I think I do 650-660MH/s with a 7970 around 1.1GHz.

 

[Dark Shroud]

Get the 7970 and oc it to 1050mhz and it will be worth it in Bitcoins.

 

[ensign_lee]

Well, ont eh plus side you'll have an extra PCIx16 slot if you upgrade, so...I guess you could? If I were you I'd just stay put though.

Them ASICs be on the horizon.

 

[thilanliyan]

I'll check when I get home. I think I do 650-660MH/s with a 7970 around 1.1GHz.

Thanks

I think my main motivation is moving to a single card since only one of my 6950s is watercooled anyway.

Although it IS tempting to get 2x7950s for the mining!

 

[Elfear]

I get about 700 Mhash with my 7970@1170/685. Total system power draw is ~270W. I actually made the switch you're contemplating (2x6950 --> 7970) and I'm pretty glad I did. At stock clocks the 6950's are faster but with overclocking things even up pretty well and in some DX11 titles the 7970 is a good bit faster. While I didn't have any major issues with Crossfire, having only one GPU has been nice.

 

[thilanliyan]

^thanks very much for the info. Yes, I think having a single card would be nice.

 

[SlowSpyder]

Thanks

I think my main motivation is moving to a single card since only one of my 6950s is watercooled anyway.

Although it IS tempting to get 2x7950s for the mining!

Been a while since I've used Bitcoin. I'm not getting any shares for some reason, I'll see if I can get it to start up. I'll let you know what I find, but I seem to remember ~660MH/sec with my 7970. I just can't remember if that was at 1GHz, 1.1GHz, or 1.2GHz. These days I settle at 1.15GHz as the performance to fan noise ratio makes me happy. If I can get this thing working, I'll let you know what I get. But I have to think it would be worth it to unload the 6950's, one 28nm chip has to be more efficient than two 40nm chips for mining.

 

[SlowSpyder]

At 1.15GHz my 7970 is bounching between 665 and 675MH/sec with no extra flags. With something there I can probably squeeze a bit more out of it.

 

[thilanliyan]

Great, thanks for the info. If I'm going for a single card I think it would be best to go with a 7970.

 

[Elfear]

Great, thanks for the info. If I'm going for a single card I think it would be best to go with a 7970.

By the way, the flags I use for Diablominer are -D 1 -v 1 -l. I researched that from January however so there may be newer advice out there for the 7000 series cards.

 

[RussianSensation]

At 1.15GHz my 7970 is bounching between 665 and 675MH/sec with no extra flags. With something there I can probably squeeze a bit more out of it.

I use GUIMiner. 1150mhz with flags -w 256 -f1 gets me 680 Mhash/sec. A single 6970 at 880mhz GPU did 390 Mhash/sec using -v -w 128 -f1

thilanliyan, if your 6950s can't be unlocked, I'd sell them and get a single 7970.

1) One of your 6950s is 1GB. Thus, the performance in future titles will be worse than it is with HD6950 2GB CF, which itself is slower than an overclocked 7970.

2) Not all games scale well with CF. HD7970 GE should be about as fast as an HD6990, sometimes faster. HD7970 > 1.05ghz would be faster in most games, especially once HD8000 series comes out and AMD focuses even more on drivers for HD7000/8000 and most likely starts to pay less attention to 5800/6900 series (which may introduce more scaling issues with CF for older cards).

3) Those 6950s may lose even more value if NV launches GTX660/660Ti at aggressive $249-299 price levels and those cards force price drops on 7850 to $199. Now is the perfect time to sell the 6950s imo, esp. since 7970 has had 2 rounds of price cuts.

I think it also depends how much you can get for those 6950s and if they are unlocked into a 6970 (which should add to resale value) and have some warranty remaining.

The other possibility is to mine with 6950s for 5 months or so (until BTC block value drops from 50 to 25) and then get an HD8970 in 2013. If you unlock the 6950s and overclock them to 880mhz, that would make more bitcoins than a single overclocked on air 7970. Because in the next 5 months, 2x 6970s will make more BTC at easier difficulty level, you may be better off making as much as possible with them:

http://www.alloscomp.com/bitcoin/calculator.php

HD6950 @ 6970 speeds x 2 = 390 x 2 = 780 Mhash = 13.62 BTC x 0.95 (assume 5% fee, i.e., BTC Guild) = 12.94
HD7970 @ 1150mhz = 680 Mhash = 11.87 BTC x 0.95 = 11.28

So 2 x HD6950 @ 6970 will make about 1.66 BTC / month more. Let's make it simple and average it to 1.5 BTC x 5 months (to mid-Dec when block value should drop from 50 to 25) = 7.5 BTC @ ~ $7 rate = $53.

So basically if you think 2x HD6950s will drop in value more than $53 and you think HD7970 will drop less than $53 from today's prices by December, it's better to buy the 7970.
If you think 2x HD6950s will drop less in value than $53 and you think HD7970 will drop way more in value than $53 from today's prices, it's better to keep the 6950s.
If you think BTC value will increase from $7, then it's also better to keep the 6950s @ 6970 speeds until December.

 

[thilanliyan]

I don't think these 6950s unlock (non-reference XFX 2gb and MSI TF3 1gb)...and I don't use XFire at all to be honest. The 1gb card is just continually mining. The 2gb is mining 90% of the time and is used for gaming about 10% of the time.

I am going to put the 6950s on Kijiji and see what I can get for them. If I can get about $300 for the both of them I may snag a 7950 and call it a day.

 

[RussianSensation]

I am going to put the 6950s on Kijiji and see what I can get for them. If I can get about $300 for the both of them I may snag a 7950 and call it a day.

You will get a performance hit though. A single 7950 can't do 650 Mhash/sec on air. I wasn't even looking to upgrade but then I thought about the impeding GTX660/660Ti launch (probably by mid-August at the latest). HD7850 may drop closer to $199. I already started seeing GTX570/6950 cards going for $180-220 CDN. Those resale levels are probably unsustainable by the end of August. If you have some BTC too, the value is up from ~$5.50 to > $8 or so from 1.5 months ago. Great time to reinvest it into a new GPU!

I didn't feel like spending $120+ on a new PSU, but if yours can support it, grab 2x 7950s. At 1100mhz, each will make about 9.5-10 BTC / month.

At that rate, with $300 from 6950's sale, the 2nd 7950 will have paid for itself in 6-7 months (assuming the current rate stays at around today's levels). I think for my next build I might get a new PSU and go with 2 GPUs. It's pretty hard to go back to NV now as long as bitcoin mining is profitable (unless their GPUs are 40-50% faster in games). I can't justify paying $400-500 for essentially the same performance that is "free" on the AMD side!

 

[thilanliyan]

You will get a performance hit though. A single 7950 can't do 650 Mhash/sec on air. I wasn't even looking to upgrade but then I thought about the impeding GTX660/660Ti launch (probably by mid-August at the latest).

Well, it will be watercooled...but yeah for mining, a 7950 would probably be a downgrade.

I seriously considered 2x7950s, but yes I would probably have to get another power supply, unless I undervolted the cards. My system mining currently (cards undervolted to 1.0v) draws only about 300w at the wall. What do you think? Would slightly undervolted 7950s run with a HX620w PSU?

And yeah it IS really hard to go to nV when my GPUs are paying for themselves!

EDIT:
You guys using 7XXX cards for mining, which miner do you use? Guiminer? I use Phoenix currently...is that no good for 7 series cards?

 

[SlowSpyder]

I am using guiminer, though I don't mine too much these days (summer heat, not sure if it is worth it... 99F today here). Wasn't there supposed to be a price drop on 7970's today?

 

[thilanliyan]

^Yeah but that price drop probably won't show up for a little bit yet?

Also, retailers were already selling cards at those prices.

 

[Dark Shroud]

Depending on what models you want or are willing to settle with you can get 7970s as cheap as $400.

http://pcpartpicker.com/parts/video-card/#c=70&sort=a5

 

[hawtdawg]

You don't want to invest in a video card for bitcoin mining at this point, come october the new Butterfly Labs ASIC units will make them completely obsolete. 40 GH/s for 1300 dollars, they'll even be selling a 3.5GH/s USB miner for 150 dollars. You'll not come anywhere close to paying it off by then and the difficulty will skyrocket in a matter of days. Just the first day's worth of preorders for the ASIC units will be equal to half of the current hash rate for the entire network.

I've had 12 6950's going for about 14 months and I'm about to start trying to get rid of all of it.

 

[thilanliyan]

^Haven't ASICs like that been talked about for a long time...but never really caught on?

 

[hawtdawg]

^Haven't ASICs like that been talked about for a long time...but never really caught on?

a legit company that already sells fpga miners is going to be selling ASIC miners come October. I've already paid for 2 of them.

 

[RussianSensation]

^Haven't ASICs like that been talked about for a long time...but never really caught on?

Ya, I don't understand it either. The current Mini Rig can do 25 GH/sec for $15,000:
http://www.butterflylabs.com/order-form-bitforce-sha256-mini-rig/

How come the major pool speeds haven't increased in the last 2-3 months at all? 1 of those rigs would pay itself off in less than a month. Because Butterfly Labs is willing to give 100% of the value of its current products towards the new October 2012 line, we should see these units fly off the shelves.

I wonder if anyone has any real world data of the current Hashing rate in Bitcoin mining for the existing Butterfly labs units?

BTW, I use GUIMiner. It works with HD7000 series and it's very easy to use:
https://bitcointalk.org/?topic=3878.0

thilanliyan, I guess it depends if you still intend to play videogames should Bitcoin mining collapse. If you do, it still makes sense to trade up HD6950s into a 7950/7970. The single GPU delivers more consistent framerates without micro-stutter and SLI/CF profiles that are necessary to extract maximum value from 2+ GPUs.

Also, I think 2x HD7950s should run fine on 620W PSU, at least on stock voltage at stock speeds. Let's say your system uses 60W at idle with minor CPU usage, that leaves 200W+ for each GPU.

Maximum power consumption for a stock 7950 is ~180W.

 

[WhoBeDaPlaya]

Currently my 2x6950s pull in about 650MH/s while undervolted at about 300w total system power (from Kill-a-Watt). Power consumption is not that much of a concern since I pay a fixed amount for utilities where I am at right now. The card would be watercooled.
Any suggestions?

You could underclock the RAM to further reduce heat and power usage. All my 6950s run at 200MHz using ATI Tray Tools.

 

[hawtdawg]

You could underclock the RAM to further reduce heat and power usage. All my 6950s run at 200MHz using ATI Tray Tools.

my hashrate starts falling off if I go below 300. what hash rates do you get with your 6950s?

also all of mine will do stock clock speed at 1000mv as opposed to 1100