Topic: Litecoin build for noobs: 3x 7950s (1.8 MH/s) in a $10 crate case - page 5. (Read 79069 times)

just putting it here for reference dual 5970 (4 cores total) on my computer pull 240*3.5=840watts ltc mining

if i am btc mining i underclock the memory to it's lowest and pull 240*3=720watts

Yes.

PSU are rated at by power they are able to deliver to the system, not at their at the wall draw.

690W at the wall at 93% efficiency means your system is delivering 690W * 0.93 = 641.7W, which means you have about 220 W of capacity left on your 860W PSU.

You could definitely put another 7950 on there.

Hi rbbrdckybk

I'm currently running 3 of the 7950's and I also have a 45w Sempron but my power monitor at the wall reads around 850w! Best case scenario is that I can use all four cards so I hope AMD FTW responds soon as I was planning to send back the psu's tomorrow. Tacotime the original poster states that his 3x 7950 crate setup only draws 625 watts.

Guys please help me out as the weekend is coming and I need to make a decision on sending the 3x AX850's back. Will undervolting make a significant reduction in power usage?

This is my setup:

MSI 7950 Twin Frozr III
AMD Sempron 145 2.8GHz 45W +heatsink/fan
Gigabyte GA-990FXA-UD5
2x 4gb ddr3
Laptop hard drive

Nice Thanks !

I run 3x MSI 7950s on an ASRock Mobo w/ Sempron 45w CPU. Using a 860w platinum Seasonic PSU (93% efficient), I pull about 690w at the wall (measured with a kill-a-watt). I run the GPUs overclocked and undervolted (1087 mV @ 1050/1400 clock speeds, although I'm not done tweaking).

850w is definitely fine for 3 cards. 4 GPUs would be a stretch.

AMD FTW you cant be running the cards at full steam (I'm not talking about overclocked). I've tried four 7950's (msi Twin Frozr) on a Gigabyte GA-990FXA-UD5 motherboard with a sempron 145
and 2x 4gb ram with a new corsair AX850 and while mining with reaper power consumption is around 1100w!!!!

Obviously the system shutdown (after about 1 min). I got the corsair AX850 because they decent, reasonably priced and based on your testimony. But there's no way from my testing (yesterday) that a corsair AX850 or any 850w psu can power 4x 7950 cards used to their potential.

AMD FTW are you lowering the 7950 voltage/core speed or something, can I get your comments?

I checked the temp on my other card, it is hovering at around 55-60C. I just put the second card in and it is the one which is working fine. The one I had in which was working fine is overheating. I tried adjusting the voltage with Trixx but no go. I don't think it is a ventilation issue and it was mining fine at this intensity prior to putting the other card in. I am wondering if it isn't a current problem with my PSU. I only have a corsair 650 80plus bronze.

Thanks to both of you, I will try this when I get home.

- give the PC a cooler environment
- give the GPU more airflow
- lower voltage/core speed
- lower intensity

cgminer  --gpu-powertune 20 will do the trick, too.

also, everyone here seems to have put their cards fairly close together. is this purely limited by extender length or does the fan air hitting the next board outweigh the accumulated radiated heat?

My guess would be that the skewed layout posted by northcape should be superior.

I did basically what you're thinking: started mining with my desktop (and wife's desktop...) and added on, and on.

You can add the 7950 alongside your 6850 and run them together. When I did that, I had to leave my case open to keep temps below 90C+.

Then, you could upgrade the 6850 to a 7950 without changing anything else. If you want to use all three cards at that point, you'll need to use a riser (x16 to x1) and you'll need either a bigger PSU or a second PSU. Since you have two x1 slots, you might be able to get a fourth card working, too. You'll probably have to move out of the P182 if you hook up three cards, and definitely if you hook up four.

i figured out the problem with Sapphire 7950 4L model cards not getting above 600kh/s.

Make sure the power limit (either in CCC or in Afterburner) is at +20%. As soon as you move that to 20% and use some known good settings and clocks you'll be all set. I'm now running ~650kh/s per card.

Hope this helps a few people.

First of all: thanks for a great guide. Did you have to post it on April 1 though? lol

Anyway, what if one already has a computer and wants to slowly add-on towards a "real" rig bit by bit, but use their regular case and parts until no longer possible?

This is my current setup. What would you start upgrading?
I'm thinking: upgrade GPU to 7950, then switch mobo, cpu, ram, and add another 7950. Then start transitioning to a similar rig as OP.

Case:   Antec P182
Mainboard :   Asus M3N-HD/HDMI
Processor :   AMD Phenom II X4 940 @ 3000 MHz
Physical Memory :   4096  MB (2 x 2048 DDR2-SDRAM )
Video Card :   AMD Radeon HD 6850
Power supply:   Corsair 620W

I built one as well, laundry baskets are awesome! The rest hoewever, not so much until now.

I run the taco build with three of those:
http://www.hardwareversand.de/articledetail.jsp?aid=75624&agid=1942&pvid=9mh401tvb_0&ref=27

After I finally got everything running, I tried mining with the first card and reaper as suggested.
Got it to disabloe CPU mining, the reaper output looked OK, apart from the fact that no matter if I used aggression 13 and 8000ish thread concurrency or 18-20 and 21712-24000 (tried everything in between with steps of 192), it would produce 100% stale shares. I immediately topped the mining pool hashrate highscore list with some 100.000k. Switching pools did not help.

I tried guiminer (scrypt-fork) and used the included cgminer with the recommended settings. 30-50% stales depending on pool and settings. Finally tried stratum pools and got < 1% stales. so far so good.

The card comes as follows:
925 clock
1250 memory clock
1250 voltage
I have catalyst 13.3 installed.

With the original clock values and voltage, the single card would fluctuate between 530-560 kh/s.
(--shaders 1792, thread concurrency 2400, vectors 1, gpu threads 1, intensity 20, worksize 256).

I thought this was ok and installed the other 2 cards. They averaged around 550 kh/s each.
Like this the rig pulled about 750 w out the wall. Naturally I tried lowering the voltage to at least approximate the 625 w acclaimed in this thread (while my cards are still far from 600 kh/s ). I used Trixx (since it's from sapphire... not sure if that's a good assumption). No success so far, it became unstable. If I tune the voltage from 1250 to 1100 while not touching clock values, the system will crash (either black screen or graphics driver resets and bad hash rates afterwards) after a few minutes. Keep in mind that with a voltage of 1100 the rig would still pull around 675 w from the wall. I turned the clock speed down to 875, still crashing with a voltage of 1100. Never even tried OVERclocking. With high electricity cost, this is disappointing.

I will try msi afterburner and 12.8 drivers next, probably experiment with reaper again, but after that I will be out of ideas.

What temperatures are acceptable? Is it obligatory to turn the fan to 100% all the time when running with unchanged clock values etc.? What temperature is too hot for the cards so they would shut down or break?

I read lots of other threads but information about fine-tuning your 7950s is scattered and incomplete. They have that blue LED button which changes the BIOS or something, but another thread said to never use that for mining so I didn't try yet. I hope someone here can offer some useful advice since it says "noobs" in the title

/edit/ it is useful to force a constant voltage?

cut back on clocks, improve circulation and if on cgminer --auto-gpu and --auto-fan

One of my cards is getting up to 90 C... how can I bring the temps down?

Since this is a noob-thread, here's a tip:
When you got a fresh install of Windows 7, and your computer goes down after a while.
Check the Power settings!

For me, it was set to "go to sleep mode" after 30 minutes of inactivity by default.
It took me a while to figure that out 

Taco, I know you are busy, but have you found any solution to that issue after using mining proxy? My entire rig no longer functions.

edit: OK, I removed my v4800 and things are working again - must have been some conflict or something.