Litecoin build for noobs: 3x 7950s (1.8 MH/s) in a $10 crate case

[tacotime]

Well that green plastic box has a ...certain charme... I seriously doubt it's open enough to provide 4 7950's with enough cool air. What temperatures do you get after half an hour ?

As I  understand it, one should aim to keep the temperature under 80 degrees c. Above 90 you are really starting to do damage.

My prototype runs up to 74c, and that's with only 2 7950's and no case at all.

Yeah you are right, the box is really bad for cooling, I couldn't run the 4 cards at max intensity, they would only stably work at intensity 13 on cgminer.

Time to cut out some windows with an old soldering iron!

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[itcamefrommars]

I can smell the plastic from here... lol.
thanks for the write up.  I'm out of date on the latest - quick boost back - thanks.

[newtothescene]

Awesome guide, really appreciate the info and tips you have here and other posts. 

One question...  Has anyone seen the PCI extension cables anywhere other than from sellers in China?  I am thinking of building one or two of these rigs but not sure I want to wait 15-28 days shipping...  Quick search on Amazon and a few other places not showing anything similar price or faster shipping to the US. 

[grue]

why do you need 8 gb of ram? cgminer barely uses 50 MB when mining (scrypt) on 2 cards.

[superdork]

NOOB QUESTION OF THE DAY........





(Wait for it)



(A)    What would happen if  I buy all the parts at microcenter and have them put it together for me?

(I have never built a computer before, I am a mac user, haven't owned a PC in about 8 years)



(B)    Would the main problem be overheating?

(C)    Could I remedy that (overheating) by installing a really good fan/cooling system?

[kuusj98]

NOOB QUESTION OF THE DAY........





(Wait for it)



(A)    What would happen if  I buy all the parts at microcenter and have them put it together for me?

(I have never built a computer before, I am a mac user, haven't owned a PC in about 8 years)



(B)    Would the main problem be overheating?

(C)    Could I remedy that (overheating) by installing a really good fan/cooling system?

A= You probably are going to pay alot of money to let them put it together for you (Really, I mean, all parts these days are plug&play, Im sure with some patient it will be set together in 1 hour)
B= If you buy the cards from a brand that has a good cooling sulution, you don't have any problem (I have Asus HD7850's, they don't get hotter than 52 Degrees on 50% fan on a monster OC and 19 Intensity, they may be 10 Dollar more expensive than other brands, but trust me, the DCII cooler saves you heat, bleeding ears and more, its totally worth the extra 10$)
C= Im not an expert on this, as my cards run godlike cool, and I don't think pointing a fan at you GFX is going to solve anything

I hope this helps you a bit.

[kcobra]

Awesome guide, really appreciate the info and tips you have here and other posts. 

One question...  Has anyone seen the PCI extension cables anywhere other than from sellers in China?  I am thinking of building one or two of these rigs but not sure I want to wait 15-28 days shipping...  Quick search on Amazon and a few other places not showing anything similar price or faster shipping to the US. 

Check Ebay. Filter by US sellers only. I ordered two extension cables last night from a seller in NJ. Cost about $6.50 each shipped.

[northcape]

Cool thread, thank you.

I received 4x 7950s and four risers on Friday and the rest of the hardware won’t get delivered until tomorrow, so I used the weekend to raid my old hardware closet and put a miner together from scrap hardware.

4x Sapphire 7950

leftovers:
Core i5 750
Asus P7P55D Premium (only 3 cards worked initially, had to do the PCI presence short on PCI-E slots 1+2 and cut the 16x extender on slot 1 down to 4x)
8GB RAM
old SATA 2.5" laptop HDD
PSU: Tagan 780W (2 cards + motherboard) and Enermax 570W Modu 87 (2 cards)

and put everything in a square laundry basket somewhat similar to yours. The PSUs fit in there as well so the whole rig is extremely portable for what it is. The graphic cards kind of slot into the holes of the crate and lock in place unless you tilt them, so it is all quite solid even without screws. I’d say this rig is more portable than all of my desktop PCs I’ve had so far.




I put the machine in a tiny room heated to 32°C with an electric space heater over night to check if it would be stable at worst case summer temperatures and all GPUs hover around 75-76°C at 65% fanspeed. It’s super cool and quiet at normal temperatures.

The laundry basket gives me around 2400 kH at 925/1250 1.000v (scrypt) or 2250 mH at 1150/1000 1.150v (SHA256).

Now I can send the ordered Ivy Bridge Celeron + Z77A-G43 + RAM + PSU back for faster ROI (if I ever get to that point, which I doubt... but mainly did it for the fun of playing with hardware and funded it entirely by cashing out a part of my BTC).

[tacotime]

why do you need 8 gb of ram? cgminer barely uses 50 MB when mining (scrypt) on 2 cards.

When you set thread concurrencies to >8192 it uses tons of ram (usually about 1.5 GB per 7950) unless that has been fixed in 2.11.4

[tacotime]

Awesome guide, really appreciate the info and tips you have here and other posts. 

One question...  Has anyone seen the PCI extension cables anywhere other than from sellers in China?  I am thinking of building one or two of these rigs but not sure I want to wait 15-28 days shipping...  Quick search on Amazon and a few other places not showing anything similar price or faster shipping to the US. 

http://www.microsatacables.com/adapters-converters/pci-pci-e-riser/ is US based, but they keep running out of risers

[rbbrdckybk]

Taco - great guide; thanks for the write-up!

One question - I have 3x MSI 7950 GPUs mining away in linux in a crate setup very similar to yours. I run them at 1050/1400, which nets me about 620kH per GPU, although I'm still tweaking the settings. As I understand it, these cards can be undervolted to save me some power. I see the option for controlling voltage in cgminer, but I have no idea what value(s) might be appropriate (and stable/safe!).

Are there any guides on the topic and/or things to be aware of? If I undervolt, am I stuck running stock clock speeds (or less)?

Thanks in advance!

[tacotime]

Hi,

undervolt with msi afterburner.

Running your cards at 1050/1400 may slow them down, try 1050/1625.  Probably you will get closer to 670 KH/s

At 1050 MHz, set voltage to 1087 mV

https://bitcointalk.org/index.php?topic=111891.0

[newtothescene]

Thank you for the info about this website selling the extension cables.  I see that this one is in stock - would these be ok (no latch) for an extension?  http://www.microsatacables.com/pci-e-16-x-riser-cable-pn-pci-e16x-rs-12in/ 

I also saw on other sites the powered adapters (added Molex) - if I go with one of those style extensions, do you know if plugging into molex power is "needed" for those to work or is it just a feature that could work if I plugged in it? 

Also - thank you for additional core/memory/volt settings.  I also have the MSI 7950 cards and will be playing around with the afterburner again to find a more optimal hashrate.  Currently seeing between 550 and 575 but would really like to get that to around 600-625 without too much heat or stress on the cards/system.

Thanks again, you have been most helpful.
New

[rbbrdckybk]

Thanks for the quick response! I'm running linux so msi afterburner unfortunately isn't an option. Do I know if it's safe to just set the voltage in cgminer?

Cgminer tells me that the memclock limit is 1575, although I didn't actually try entering a number higher than that.

Hi,

undervolt with msi afterburner.

Running your cards at 1050/1400 may slow them down, try 1050/1625.  Probably you will get closer to 670 KH/s

At 1050 MHz, set voltage to 1087 mV

https://bitcointalk.org/index.php?topic=111891.0

[rbbrdckybk]

So it turns out that cgminer can't actually control the voltage - it's based on AMD's ADL, which apparently won't make voltage changes stick, at least not with my 7950s.

Does anyone know if there is a linux-based tool that will let you set the voltage on the Radeon 7xxx series cards?

If not, I think that is a serious negative on the linux side of the OS decision for anyone considering building one of these things.

[northcape]

Hi,

undervolt with msi afterburner.

Running your cards at 1050/1400 may slow them down, try 1050/1625.  Probably you will get closer to 670 KH/s

At 1050 MHz, set voltage to 1087 mV

https://bitcointalk.org/index.php?topic=111891.0

Is there a next lower recommended clockspeed for gpu and memory?

I’m wondering because 925/1250/0.950 gives me ~560 KH/s per card but 1050/1625 makes the rig unstable, even at 1.250v.

I’ve tried other combinations in between, targeting a 0.6-0.7 ratio, but they all end up being slower than the "sweet spot" 925/1250 or horribly inefficient (1100/1550/1.250 gives me 580 KH/s at WAY higher power draw)

I suppose the memory of one of the cards can’t handle 1650 Mhz, maybe I should single that one out and try to run the rest at your recommended clock speeds. SHA256 hashing works fine on all four cards 1220 Mhz GPU.

[grue]

why do you need 8 gb of ram? cgminer barely uses 50 MB when mining (scrypt) on 2 cards.

When you set thread concurrencies to >8192 it uses tons of ram (usually about 1.5 GB per 7950) unless that has been fixed in 2.11.4

I'm using thread-concurrency 6500 on 2 cards, and it's only 50 mb for both. So unless memory usage grows exponentially with thread-concurrency, the memory usage shouldn't be that high.

[tex83rb]

hello, what do you think about this configuration


SAPPHIRE - Radeon HD 7970 3 GB   357,99   x   4   1431,96 €
            
            
            
            
CORSAIR - Memoria Dimm Vengeance 16GB            119,99 €
            
            
ASUS - Motherboard P8Z77-V PREMIUM            411 €
            
            
            
THERMALTAKE - Chaser MK-1            109,99 €
            
            
            
INTEL - Processore Core i7-3770K            309,99 €
            
            
COOLERMASTER - Alimentatore Silent Pro Hybrid 1300W      233,99 €
            
CORSAIR - Dissipatore a Liquido Hydro H100i             106,49 €
            
            
total             2723,41 €




what could i reach mining LTC?

2,4 Mhash/s ?

it's worth this expense?


actually i'm mining on coinotron with 5850 at 279.6 KH it calculates around 1.198 ltc/day.

with that build it would be 8 times  around... so at current conditions would be theorically 9,584 LTC/day

at current rates it would be

4.30 $ / ltc

so around 41 $ / day


in € is 31,5 € / day


withouth considering power expenses at current conditions 2723,41 € / 31,5  (€ / day)  = around 86 days to fullfill the investment...

i'm wrong???

and after all if conditions changes and the system wouldn't be convenient anymore i can always resell the whole structure and getting back some money , at least 50 % ....   it will be business risk  the possible lost of money....

please comment

[Herbalconfusion]

Seems like you are spending more then you have to. Just my opinion. I think you could get 2 rigs running for that cost. Try ordering from a different website.

[tex83rb]

could you extimate the expense of this configuration with 1300W of power for 24h/24

at the moment i pay 0,16 €/ KWh