Bitcoin Forum

I didn't know if this goes in mining or in alt currencies, so I guessed here. I am thinking about building a rig for mining alt coins (scrypt ones). I have some questions and I would really appreciate their answers :D:

• exactly which card is best in terms of power/hashrate for mining (I pay $.13/kwh)?
• for the best card, how much power does it consume and what hashrate does it produce?
• can I CPU mine and GPU mine at the same time (does it affect the GPUs)?
• can rigs still efficiently function while GPU mining with 6 GPUs (windows 8 64 bit)?
• what is the best PSU (or combination of two PSUs) for 6 of the best GPUs plus a maxed out i7 3770k?

Thanks :)

1. Not a comprehensive assessment, but the Gigabyte 7950 (http://www.amazon.com/Gigabyte-Mini-Displayport-PCI-Express-Graphic-GV-R795WF3-3GD/dp/B007581QHG/) seems pretty popular for Litecoin miners.  This topic (https://forum.litecoin.net/index.php/topic,2641.0.html) explains how to reduce power consumption and boost the card's performance. (~600 MH/s)

2. Probably about 600-650 MH/s/card, and about 250-300 watts/card with proper firmware and overclocking settings.  Unfortunately I've seen reports that newer models of that card are voltage-locked which means your power consumption will be about 300w unless you flash a hacked firmware image. (I never tried this since I read about it after I stopped ltc mining)  The author of the topic I linked above got 668 MH/s/card; I was able to get about 640 MH/s for a few minutes but my cooling was inadequate so the card had to slow down to avoid overheating.  So, probably about 650 MH/s with proper cooling. ;)

3. CPU mining at the same time might be okay, but probably isn't worth it.  I would recommend reserving at least one core (i.e., not mining with one core) for the system otherwise the machine will be just about unusable.  You probably don't want to CPU mine though since it will use ~50w more power (if not more) and generate you a marginal amount of coins. 

4. It depends on your configuration.  The higher you set the intensity, the lower your video performance but the faster your mining performance will be.  You can set the intensity of all the cards not attached to a monitor to maximize mining performance, and compromise on the intensity for the card running your display(s) so you can still use the machine. 

5. Everyone around here seems to speak highly of Seasonic PSUs.  I'm running one right now and it's never given me any issues, but I'm sure there are other PSU brands that are also good.  (I think some Corsair and maybe OCZ PSUs are actually made by Seasonic)
I would stick with a name brand well known for quality, and would probably get two 1000-watt units.  Maybe 2x 1200w to be safe, but it might be overkill.  As for efficiency, get at least an 80 PLUS Silver PSU; I'd recommend a Gold or Platinum though. (80 PLUS Efficiency details (http://en.wikipedia.org/wiki/80_Plus#Efficiency_level_certifications))
6x 250w per GPU (conservative estimate) + ~100 watts for the rest of the system is 1600 watts.  There aren't many PSUs rated this high and you can't safely run a 1600-watt load on one 120v 15a circuit continuously according to US electric code. (probably similar in other countries?)
Two of these would run the system with no problems: http://www.amazon.com/Seasonic-SS-1250XM-X-Series-Power-Supply/dp/B00607JLWU/

Good luck!

Personally for me its the Gigabyte 7950.  I love my sapphire's when i bitcoined.   But Scrypt i would give giga slight lead.

I agree with the above two posts, for the price, a Gigabyte Radeon HD7950 would be a great overall card for scrypt mining. But if you look around online, you can get the HD7970 for the same price if not cheaper. Personally, I've snagged a few HD7970's for between $250 and $300 each (about 8, all Gigabyte mind you, no more than 6 months old), which is relatively cheaper than the 7950's. The warranty on the Gigabytes are amazing too, because they go up to 3 years, by the serial number.

tl;dr: If you can find some used Gigabyte HD7970's around the $250 to $300 mark (offer online, ebay, etc) you'd get a hash rate of about 750kh/s for about the same cost as a new 7950 or less. Good luck!

"Bump"

I'm about to retire old graphic cards.  I'm not going to farm-mine Scrypt, but it'd be nice to have a card mining when it's not being used.  Would the above July advice still be good advice here In October?

Nice write up to have there, but I have something to add.

1) Gigabyte 7950 is voltage locked. So if you plan to reduce your voltage, you have to get other brand like Sapphire and MSI. R9-280x seems to be a good choice to as the price is quite good for a new model.

2) You might wanna wait for the R9-290x to launch before you make any decision, they might be the best in term of price per hash.

3) Unfortunately, there are a lot of scrypt FGPA development going on. If you bought it and later they realise it, you will be in big trouble...

Thats all :)

17 page review on the new R9's bench marked with Bitcoin mining.

http://www.tomshardware.com/reviews/radeon-r9-280x-r9-270x-r7-260x,3635.html

Great write up on the GB 7950.


~BCX~

I noticed they are only getting 1000 on a 7990, I've been able to get 1500 kh/s on scrypt.
if they are getting 620 on a 280x, I think i can get 800 kh/s, but I won't find out till friday when my 280x gets here.

Still waiting for R9-290x, It might be the best!!

800 is possible with a great card (have done it with 7970s) but the power consumption doesn't make sense compared to running an easy 740KH/s.

Precisely,

A lot of people think hashrate is all that matters, you have to also look at efficiency in mining and power cost.

For example

A 7950 running 660 mhs at 490 wu which is common on 7950's at the hash rate isn't mining as many coins as 7950 at 550 mhs and 525 wu. The lower hashrate not only mines more coins, it uses a lot less power and generates a lot less heat.

As some one who has been running with 7950's since the first day they came out and currently has 63 of them, I've found no substantial benefit in long term mining above stock clocks. CKolivas, the dev for CGMINER has found the same to be true.

With all of that being said, the last 7950 I bought was a year ago before diving huge into ASICs.


~BCX~

Used 7950's... Avoid Power Color and XFX.

I would avoid Power Color and XFX new!

Total POS


~BCX~

I have two sapphire 280x cards, both do 750 at 1085/1500.

Why not wait for someone to share R 290x info before deciding..

 Unless something has changed the most energy efficient are 7950's, and it's not even close compared to others!


Best Brand 7950:
===========

Asus 7950 are extremely well built, @ modest voltage of 1.09v, run flawlessly. Best of breed. But often tough to find in stock.

Toss in MSI Afterburner software, overclock up to 1050/1500, or slightly less at 1015/1450 and you will be fine as long as you have cooling issues solved. Temps will range from @ 70c - 75c depending on cooling and room temp.

 As for CPU (AMD APU) mining with a few 7950's, can cause instability when system is handled manually. Best not with a few cards but...

 Other cards may prove okay too but these Asus cards are quite impressive when it comes to build quality to say the least. Just hard to find in the past.

 Check out the Asus 7950, no one yet has offered a bad review of them at newegg.com last I checked, and that's very telling.



 Where as every other brand of 7950's have had issues with some/many batches of their 7950 cards.

 Seems build quality is a real issue with nearly all brands using  AMD 7950 GPU's, with the sole exception of Asus so far.

 But don't bother with the Asus software.

 Go to AMD and download the drivers there.

 Just realize each Asus 7950 hog about 3 slots width, more than others, built extremely beefy, heavy duty to say the least.  But their not as long as some so that they will prove a bit more useful later to a wider audience. Their also less noisy compared to some, run extremely stable, and have been completely problem free. Voltage is lower than others too which is a good thing. But they are voltage locked. Then again that didn't prove to be a problem either.



Caveat emptor - let the buyer beware!