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Author Topic: First power bill for my 6 GH/s rig  (Read 9373 times)
bitcool
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March 14, 2012, 04:37:36 AM
 #101

my god

did you really just go out in your back yard and put a box fan in your neighbors dog house to win an argument on line?

I will pay 5 BTC bounty for photo proof there is six 5970s mining inside there.

I have to see it.


Okay, I just went to my backyard, negotiated with my neighbor's dog, he was kind enough letting me put the fan back in, along with fake LEDs, and took a picture -- but it looks beautiful, doesn't it? 


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March 14, 2012, 05:32:34 AM
 #102

Okay, sick of this discussion, so I did the math.  Go ahead and carry on arguing with it, without me.

Repeating my earlier point, the average bedroom measures a mere 86ft^2, or roughly 600ft^3, Meaning a 2400CFM box fan will completely remove the air from the room every 15 seconds.  Two will then do the job every 7.5 seconds.

1 BTU will heat 55 ft^3 of air (at STP and H) by 1F.  20KW = 68290BTU/hr.

20KW will therefore heat 3755950 ft^3 per hour, or 62600 ft^3 per minute, or 7825 ft^3 per 7.5 seconds, by a single Fahrenheit degree.  Or, put more usefully, it will heat 600ft^3 by 13F every 7.5 seconds;  At 4800CFM (one full air-exchange per 7.5 seconds), that gives us a mean-over-time rise of 6.5F - Pretty damned close to my "feels 5F warmer" estimate from the woodstove.  Funny, that.

For the rest of this, I will refer to the Radeon 6990, the hottest single card (AFAIK) in common use.  Your "preferences" of running cooler than spec aside, a Radeon HD 6970 (and the 6990 just contains two downclocked 6970 Cayman chips) has a tMax of 194F.

Now we have an interesting result here - With the stock cooler and under full load, a 6990 will violate its own spec at ANY ambient over 73F.  This would make the naysayers appear correct...

But!  We've also demonstrated that two box fans will clear 20KW of heat from a room, with a 6.5F steady-state rise.  That reduces the problem to airflow at the ambient/heatsink interface.

Since we've limited this discussion to airflow, I'll limit the following to fan/heatsink combos only.  Using a halfway decent aftermarket cooler, you can drop the under-load temperature to below 160F (you can find similar numbers in dozens of articles on Tom's Hardware or AnandTech, if you like - For my exact source, I found http://www.kitguru.net/components/graphic-cards/zardon/arctic-cooling-accelero-twin-turbo-6990-cooler-review/5/ helpful in that it described the test conditions sufficiently well to extrapolate from them), for a plausible under-load delta-T of a mere 87F.

This, then, gives us a "feasibility" result of 107F at the intake, or a raw outside temperature of 100.5F.

Call that a win or a lose, as you like.  Where I live (if I didn't pay a fortune for electricity), it would put me over my "thermal budget" for two days in the past decade (no, DeathAndTaxes, not talking about winter, nor did I ever).  And I don't live in Sweden.   Tongue


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March 14, 2012, 02:05:07 PM
 #103

I call it lose.  The claim being disputed didn't involve aftermarket heatsinks.  Especially not .... $140 aftermarket heatsinks.

20KW of 6990 @ 1KW per quad 6990 system = 80 GPUs.  $140 aftermarket heat sink * 80 = $11,200 in heatsinks.  

So using $11,200 in aftermarket coolers one could keep the cards at not so comfortable 90C.  Using stock heat sinks temps would be beyond the hard thermal throttle limit.  That at least sounds plausible.  Nobody said cooling was impossible under any circumstances.  The claim made earlier in the thread was bogus and you just proved it.  Even with 10 grand in cooling gear the cards will be extremely hot.  Mining at 90C isn't going to produce stable efficient rigs.  You also need to account for the fact that PSU efficiency declines rapidly when ambient is >80F which is going to add extra load, wasted energy, and even more heat.  

Still interesting analysis.  BTW I am building a watercooled server rack to cool 20GH/s without airconditioning in 100F temps.  Obviously I don't think it is "impossible" but you have demonstrated the claim made by up thread is impossible.  Thanks.

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March 14, 2012, 11:51:00 PM
 #104

Okay, I don't care to get sucked back into this, but in the interest of extending an olive branch...

You also need to account for the fact that PSU efficiency declines rapidly when ambient is >80F which is going to add extra load, wasted energy, and even more heat. 

Ambient doesn't ever hit 80C under my scenario.  It peaks at "real" ambient plus 6.5F (3.6C).  So you have no worries about your PSU or VRMs or CPU or NB or SB or anything except the GPU cores themselves.  I don't point this out defensively, but as a positive, because...


BTW I am building a watercooled server rack to cool 20GH/s without airconditioning in 100F temps.  Obviously I don't think it is "impossible" but you have demonstrated the claim made by up thread is impossible.  Thanks.

Aside from the fact that I never claimed 110F (okay, a bit defensive), you can read my numbers on a more positive note relevant to your project.  I didn't prove it as "impossible", but rather, a function of the GPU cooling device itself.  Your idea of using a water cooler should nicely get around that limitation, easily buying you another 15-20C with which to play.  That puts you solidly in the feasibility range up to an ambient of 134.5F

Again, though, you make a good point about cost.  It still makes more sense to me to just throttle your mining rigs down over a certain temperature, than to go for a complex, expensive per-GPU cooling solution.

I don't beg - If I do something to deserve your BTC, you can find my address on the invoice.  Wink
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March 15, 2012, 12:28:16 AM
 #105

I call it lose.  The claim being disputed didn't involve aftermarket heatsinks.  Especially not .... $140 aftermarket heatsinks.

The claim dispute may or may not involve aftermarket heat-sinks (which are availible for under $100 btw, your shopping skills suck), as the post didn't specify.  Also, the claim in dispute included an additional fan for every rig.  In addition, there was this little gem which you completely ignore-

Quote
It gets into the high 90's and occasionally the low 100's here in the summer (desert climate).  I used a small evap cooler last year during the summer

So okay.  Assuming he doesn't have the custom heat sinks is already a stretch in your favor.  But given that, you honestly don't think the addition of an extra fan per rig AND an evap cooler would be enough to compensate for lack of said heat sinks?

A quick google on evaporative coolers provided this bit-

Quote
EVAPORATIVE COOLING
How an Evaporative Cooler Works

In the Arizona desert in the 1920s, people would often sleep outside on screened-in sleeping porches during the summer. On hot nights, bed sheets or blankets soaked in water would be hung inside of the screens. Whirling electric fans would pull the night air through the moist cloth to cool the room.

That concept, slightly more refined, became the evaporative coolers that to this day provide a low-cost, low-technology alternative to refrigerated air conditioning.

An evaporative cooler produces effective cooling by combining a natural process - water evaporation - with a simple, reliable air-moving system. Fresh outside air is pulled through moist pads where it is cooled by evaporation and circulated through a house or building by a large blower. As this happens, the temperature of the outside air can be lowered as much as 30 degrees.

While I am sure 30 degrees is a bit of an extreme case, I don't think it would be too crazy to assume that an evap cooler could lower the incoming air by 10-15F, which would more than make up for the difference accounted by those oh so expensive heatsinks.

Calling it a lose is wishful thinking, or a desperate act of someone who knows he was proven wrong Tongue

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March 15, 2012, 12:32:55 AM
 #106

I call it lose.  The claim being disputed didn't involve aftermarket heatsinks.  Especially not .... $140 aftermarket heatsinks.

The claim dispute may or may not involve aftermarket heat-sinks, as the post didn't specify.  Also, the claim in dispute included an additional fan for every rig.  In addition, there was this little gem which you completely ignore-

Quote
It gets into the high 90's and occasionally the low 100's here in the summer (desert climate).  I used a small evap cooler last year during the summer

So okay.  Assuming he doesn't have the custom heat sinks is already a stretch in your favor.  But given that, you honestly don't think the addition of an extra fan per rig AND an evap cooler would be enough to compensate for lack of said heat sinks?

Calling it a lose is wishful thinking, or a desperate act of someone who knows he was proven wrong Tongue
Listen, I give up. Is that what you wanted to hear? Good for you, you win. Yay. Now please drop it because this is beyond a joke. I'll keep cooling how I want to, and you can keep cooling how you want to.

Mods, could the offtopic be split off? OP, sorry for ruining your thread.

Mining Rig Extraordinaire - the Trenton BPX6806 18-slot PCIe backplane [PICS] Dead project is dead, all hail the coming of the mighty ASIC!
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March 15, 2012, 02:17:44 AM
 #107

my god

did you really just go out in your back yard and put a box fan in your neighbors dog house to win an argument on line?

I will pay 5 BTC bounty for photo proof there is six 5970s mining inside there.

I have to see it.


Okay, I just went to my backyard, negotiated with my neighbor's dog, he was kind enough letting me put the fan back in, along with fake LEDs, and took a picture -- but it looks beautiful, doesn't it? 




lol

now I REALLY dont believe you!
I will pay 20 BTC bounty if you take pictures of 6 5970s mining in that dog house.
bitcool
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March 15, 2012, 03:26:50 AM
 #108

my god

did you really just go out in your back yard and put a box fan in your neighbors dog house to win an argument on line?

I will pay 5 BTC bounty for photo proof there is six 5970s mining inside there.

I have to see it.


Okay, I just went to my backyard, negotiated with my neighbor's dog, he was kind enough letting me put the fan back in, along with fake LEDs, and took a picture -- but it looks beautiful, doesn't it?  

http://i1133.photobucket.com/albums/m586/bitcool5/IMAG0196.jpg


lol

now I REALLY dont believe you!
I will pay 20 BTC bounty if you take pictures of 6 5970s mining in that dog house.
I am in.
Specify what kind of pictures will satisfy you as "photo proof"?

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March 15, 2012, 07:30:45 PM
 #109




Quote
Wood From my Basement = FREE
Various Pipes, Valves, & Pressure Gauges (Stolen from my neighbors basement) = FREE
Hamster Wheel = $2.99 (used salvation army)
Hamster = $4.99 (Pet Shop)

Currently its getting about 1 Mhash per bag of Hamster Food
but im looking into ways to make it more efficient
(rats, mice, racoons etc)

if you guys are so smart than tell me how I can keep my latest rig cool!

at first I was giving the hamster water and then I switched to gatorade

now when I stick a anal thermometer up his ass hes registering about 50c which was still cooler than my 5970 but id like to see it a little cooler

I don't think I laugthed so hard in a long time... and not those fake LOL... but a real LOL that lasted almost a minute
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March 15, 2012, 07:41:17 PM
 #110

Okay, I don't care to get sucked back into this, but in the interest of extending an olive branch...

Sounds good actually I didn't realize you and someone else in the thread weren't the same person.
Your analysis at least involved some thought and pointed out some bottlenecks in cooling with high ambient temps.

Quote
You also need to account for the fact that PSU efficiency declines rapidly when ambient is >80F which is going to add extra load, wasted energy, and even more heat. 

Ambient doesn't ever hit 80C under my scenario. 

I was saying 80F.  Temps >80F aren't "bad" for a PSU but efficiency starts to decline rapidly.  Likely shouldn't have switched units like that.  Hot PSU are less efficient resulting in more current adding more heat and making them less efficient.  At some point you need to consider the increased energy costs from high ambient temps.
Quote
Aside from the fact that I never claimed 110F (okay, a bit defensive), you can read my numbers on a more positive note relevant to your project.

Yeah more of that confusing two people as the same person.  Should have been obvious although you disagreed your posts at least has some factual basis to them.

Quote
Again, though, you make a good point about cost.  It still makes more sense to me to just throttle your mining rigs down over a certain temperature, than to go for a complex, expensive per-GPU cooling solution.

Which fits in to my water cooled rigs also.  If my setup provides good cooling at max load 350 days out of the year then it makes more sense to just throttle down the hottest 16 or so days (or parts of those days).  The nice thing is cgminer makes it too easy.  "auto-gpu" : true and provide a clock rate range.  As ambient increases the temp in the loop increases.  Once it gets over target temp the cgminer will start to clock down the cards.

I saw this in effect on my test rig (the radiator is way undersized for the heat load).  It works flawlessly.  So super hot days simply mean the farm in aggregate might be running at 90% of peak instead of 100%.
bitcool
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March 15, 2012, 10:30:29 PM
 #111

my god

did you really just go out in your back yard and put a box fan in your neighbors dog house to win an argument on line?

I will pay 5 BTC bounty for photo proof there is six 5970s mining inside there.

I have to see it.


Okay, I just went to my backyard, negotiated with my neighbor's dog, he was kind enough letting me put the fan back in, along with fake LEDs, and took a picture -- but it looks beautiful, doesn't it? 

http://i1133.photobucket.com/albums/m586/bitcool5/IMAG0196.jpg


lol

now I REALLY dont believe you!
I will pay 20 BTC bounty if you take pictures of 6 5970s mining in that dog house.
In all seriousness, or just trolling?
bitcool
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March 18, 2012, 12:31:30 AM
 #112

my god

did you really just go out in your back yard and put a box fan in your neighbors dog house to win an argument on line?

I will pay 5 BTC bounty for photo proof there is six 5970s mining inside there.

I have to see it.


Okay, I just went to my backyard, negotiated with my neighbor's dog, he was kind enough letting me put the fan back in, along with fake LEDs, and took a picture -- but it looks beautiful, doesn't it? 

http://i1133.photobucket.com/albums/m586/bitcool5/IMAG0196.jpg


lol

now I REALLY dont believe you!
I will pay 20 BTC bounty if you take pictures of 6 5970s mining in that dog house.
Go ahead, order a dog house and try it yourself.
Every miners in  Canada or close to the Canadian borders  should do this Wink  don't waste money on AC, electricty and room space.
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