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
:
- 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 seems pretty popular for Litecoin miners.
This topic 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)
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!