LTC Mining - 6 GPUs?

[elliotp]

Until ASICs are a bit more available for BTC i'm thinking i'm going to go for LTC with GPUs for now.  I do have the option of free power at work (providing the machines are quiet enough)

Is it possible to get 6 GPU's in one rig?  I'm thinking 6 x Gigabyte 7950's  on a Gigabyte Motherboard which has 5 x 16X PCIE and 1 x 1X PCIE?  Obviously using passive extenders to seperate the cards, and one converter to 1x to 16x?  And a big ass PSU.

[1715077143]

1715077143

[1715077143]

1715077143

[kohonez]

could be inestable, i would recommend you a 3X or 4X GPU setup.

[saneczki]

True better take max 4 gpu. More is ineffective. I also throw some gpu to ltc

[elliotp]

True better take max 4 gpu. More is ineffective. I also throw some gpu to ltc

Ok, well i guess i can do 2 x 4 systems - keep things simple.

What sort of GPU and PSUs do you use?  I take it for a 4x system i'm wanting a 1200watt good brand?  Also do you need an active riser for the 4th? OR can you get away with 4 passive risers?

[saneczki]

1200W is quiet OK but I You can buy 1300+ it will be more safty. When You will start PC BIOS and before loading systems with 4 gpus it will use max power (no economy set) so some ppl have problem to start. IT S ALL DEPEND IF YOU WILL OC Voltage and MAX GPU and MEM GPU settings. If You want overclock voltage and all Mhz to max 1200w can be too weak.

http://www.tomshardware.co.uk/forum/338356-28-enermax-1200w-platimax

Good PSU antec 1200 HCP,  Platimax 1200,  Corsair AX 1200, Enermax lepa 1600, xfx 1250, and some another

http://www.techpowerup.com/reviews/LEPA/G1600-MA/ Take a look tests there a lot of tested PSU and very good level of testing !

https://bitcointalk.org/index.php?topic=82120.0   < 4x7970

BTC dont need a lot of MEM mhz,   LTC NEED MAX memory and quiet HIGH or MAX GPU mhz so more power in ltc

Good luck

[Duetschpire]

1200W is quiet OK but I You can buy 1300+ it will be more safty. When You will start PC BIOS and before loading systems with 4 gpus it will use max power (no economy set) so some ppl have problem to start. IT S ALL DEPEND IF YOU WILL OC Voltage and MAX GPU and MEM GPU settings. If You want overclock voltage and all Mhz to max 1200w can be too weak.

I didn't know that OCing the GPU starts with BIOS, I'm still new to all of this, but I come from desktop support and the OCing is happening on a software level. Am I wrong?

[saneczki]

No. Its true OC gpu is from software To bitcoin 1200W PSU for 4x7970 OC gpu / mem downclock is OK. To max OC gpus to litecoin it need more power. Its more safty use higher W PSU. Anyone have expirience with 1200w 4x7970 and LTC ?

[mercSuey]

Agreed, memory work requires more power.

[FiatKiller]

Get a gold-rated PS no matter what.

You do know that you could be fired for doing that at work, right? It has happened to people.
You are essentially stealing power. Better to maybe approach the boss and promote as a way
to make money and you get a % or a raise for the idea.

[xandriel]

Would 7950's not be better, like the OP originally stated?
Seems to me the 50% saving on hardware cost would outweigh the benefit from the 7970 cards. You could afford 6 x 7950 for the price of 4 x 7970

[FiatKiller]

The thing that people always forget is that in 6-8 months, the rig will be paid-off. After that your only cost is electricity. At that point hashing power is all that matters. Hopefully it will run for maybe 3 years and all those extra shares will really add up!  :-D

[daytrader420]

Get a gold-rated PS no matter what.

Can I ask, why you recommend gold PSU no matter what? I've heard others recommend silver or gold also.
Personally I got a bronze rated PSU (900w , running 3x7950) and I'm not sure if it's good or bad.

@op sorry to hijack thread.

[MorePork]

Get a gold-rated PS no matter what.

Can I ask, why you recommend gold PSU no matter what? I've heard others recommend silver or gold also.
Personally I got a bronze rated PSU (900w , running 3x7950) and I'm not sure if it's good or bad.

@op sorry to hijack thread.

That's a good question, bronze, silver and gold are just efficiency ratings.  The lower the efficiency the higher wattage you need the PSU to support for the same load (you never want to max out the PSU at full load).  The second side is higher efficiency means less loss to heat which may be a consideration.  Although the PSU is going to produce far less heat than a stack of GPUs so it may be a moot point.

In the end its probably best to pick based on cost ratio, lots of gold PSUs are considerably more expensive and may not be worth it over just getting a higher wattage bronze to make up for the efficiency loss.  Check the specs and figure it out from there.

[jtmart007]

Also, some 7950s and 7970s take BIOS flashes to reduce stock voltage or clocks if they are "locked" and reducing those numbers could lower heat output and power draw on your PSU. I did that to 2 of my 7950s so far and dropped 12c off of each one of them, in addition to lowering the "locked" voltage from 1.250 to 1.09 - still stable at previous clocks, too.

[FiatKiller]

If gold is more efficient then that is best. Long-term your ONLY cost is electricity!

http://www.corsair.com/en/blog/80-plus-platinum-what-does-it-mean-and-what-is-the-benefit-to-me

[gudmunsn]

Also, some 7950s and 7970s take BIOS flashes to reduce stock voltage or clocks if they are "locked" and reducing those numbers could lower heat output and power draw on your PSU. I did that to 2 of my 7950s so far and dropped 12c off of each one of them, in addition to lowering the "locked" voltage from 1.250 to 1.09 - still stable at previous clocks, too.

Any idea how to unlock sapphire 7950's? Is there a good site with flash software somewhere?