100% depends on what you are mining. My 1080's(each) will mine more the $$ than 2 RX5870 or 580s mine and costs less than 2 RX570s or 580s so its not econimally intelligent to buy 2 rx anything over a 1080 UNLESS you have to mine a specific AMD friendly algo for whatever reason.

Power phase from a Direct Current power supply huh?  The inherent traits of a AC-DC switching power supply is that the output is directly isolated from the input.  There is no such thing as phase on the DC side of a power supply.

The reason they dont want you to mix power supply feeds that are powering different GPU banks (A, B, C) is so you dont have bank A trying to draw off of B power supply which can lead to excessive current amounts flowing in conductive traces of the motherboard.  Amounts of current that are actually higher than what the board traces are rated for.  Get in that situation and your traces on the motherboard will become a fusible link and burn open.

A fan is $10-$15 to replace.  Let that GPU burn up and see how much it costs to replace then!  No reason a GPU should be ran at 76C or above unless you live in the Jungles of Vietnam.

3 phase is more efficient....on 3 phase equipment. With a 3 phase building you will end up with a substantial amount of available power because there are 3 legs of power coming in instead of just 2 like in a home.  ANYTIME you step down or up power you end up with less efficiency...that loss is in the form of heat at the transformer. This is why no power supply is 100% efficient.  208 3 phase is what you want over a 480 3 phase power input.  208 3 phase has 120v to ground from each leg OR 208v across any two legs.  480 3 phase is 277v from each of 3 legs to ground or 480v across any 2 legs.  You wouldnt need a stepdown transformer for a 208v 3 phase building. You would be good to go just know that you CANNOT use anything that an electrical motor rated for 240vac (marked 220/230/240) in that building that has 208 3 phase.  They will burn up in very short order.  Now your power supplies will be fat dumb and happy in a 208 3 phase building.  You can run each power feed off of one leg to ground OR you could run them off of 2 phases which would yield 208v.

Heres some free but good advice....  If you have windows in your mining room, cover the windows so the sun cannot shine into the room.  The sun adds radiant heat and can heat a room up very fast!  Use curtains, blinds or even tint, cardboard or paint the glass on the windows.

I doubt your incoming power to your apt is 400v. 

My rig 1 B250 Asus ME board has this same glitch when you click on windows/start button too. This rig has 6 AMD cards on it and 2 Nvidia.

This week there has been an obvious delivery of GPU's into the United States.  Many brands, models are available and many of them are substantially lower in price (for the circumstances anyway).  Most deals Ive seen are at newegg.  I just bought a MSI 1080 for $619 and i get a $10 rebate on top of that.  Bought Wed this week.  Many RX series cards are available way more often than ive seen in the previous couple weeks or so.  Its going to get worse again very soon with BTC hanging out in the $11,000 range and much speculation that it will only climb this month reaching 15k plus. We shall see and im all for it.  I like $$$.

My free advice....Buy as many GPUs as you can afford and get your hands on.  But be smart and dont pay too much for them.  In other words dont pay $300 for a 1050 TI. Pay $235 or less.  Dont pay $999 for a 1080.  Pay under $700.  The deals are there....just have to be quick and know what your limit for each model should be.

My rig 2 is running 10 Nvidia Cards but will show red on the 11th card if added.  Im running windows 10 pro updated to 1709.  Bios is up to date.  8gb (4gb in each slot).  Runs flawlessly with 10 cards and its a set it and forget rig until you stick that 11th card in then it will not see it in device manager.  So i obviously didnt follow the owners manual about mixing in AMD cards (I only own 8 AMD cards and they are on a nother B250 m/b).  Has anyone else had this no 11th card recognize problem?

Say what? "You could easily calculate what amperage you have coming in"?   The amount of current coming is totally dependent on what the load is.  In this case the load would be rigs, lights, fans, etc.  You cant have any current flow without a load.

A cheap harbor freight infrared thermometer is your friend.  Check all connection with the IR Thermometer.  If one is loose then its temperature will be 5-10 degrees plus higher than the rest.  This check can only be performed when there are loads connected to the breaker panel. (AKA branch circuits connected to your (branch) circuit breakers.  Use proper electrical safety when working in an electrical panel at all times!

OP....You just call the power company that feeds power to the building and ask them what the service entrance feed from the pole is rated for.  Goto your main panel and check the main breaker rating and take that number and multiply that by your service voltage and that answer will be your total watts. Your main panel will tell you what your voltage is most likely if all the stickers are still there.  Then multiply total watts by .80 (80%) which is the 20% derating amount for constant duty cycle.  

Heres an example for a typical U.S. household.

200amp main breaker  240vac service entrance feed.

200 x 240 = 48000 watts.

48000 x .80 = 38400 watts Total Watts available for constant Duty Cycle.

Do not think you will use a power cable to feed equipment that is rated for say 20amps and think it will be ok to run 18Amps continuously 24/7. Remember the 80% rule of derating for constant duty cycle.

Basic electrical math formulas

Power (w) =  E (volts) x I (Amps)    P=ExI

E (volts) = Power (w) / I (Amps)     E=P/I

I (amps) = Power (w) / E (volts)     I=P/E

I=Current   P=Power  E=Voltage

Now there is also a possibility that this warehouse has 3 phase power and thats a whole different ballgame.  Could be 208 3 phase, 480 3 phase and even bigger depending on what the building was used for over the years.  You should have checked to see what the power input to the building was before you leased it.  If its 3 phase then you are screwed because you will need alot of step down transformers and your efficiency will be down in the weeds.  208 3 phase is 120v to ground from each leg to ground. You cannot get 240v from 208 3 phase without very expensive step up transformers.

You are contradicting yourself.  For the new cards to sellout they have to be available and SOMEONE has to buy them. WTF, Over.

I have to disagree but there are qualifying limitations to my disagreement.  The main factor being money.  If someone has the PCIE slots available in a rig(s) then buy anything they can afford. Fill them up and have them earning money NOW until the next generation cards come.  Then when the 10 series prices come down ....If the nextgen cards cause that to happen once released buy those and dumps the 9 series on ebay for whatever they bring BUT if you have the PCIE space available after buying 10 series then use the 9's too. FK it....build a rig just for the 9 series cards. The more rigs/cards running the more money you are earning daily.

Buying a vega 56 or 64 is false economy.  They do not produce enough for what they cost.  The only thing they are good for is if someone has limitations to the amount of cards they can support with motherboard(s) or power supplies.  In those cases stuff your rig(s) with Vega 56/64.....if you have the money for those AND have limitations making you have to go that route.

Im running 10 GTX (1080, 1060, 1060 and the balance in 1050TI) on my Asus B250 Mining Expert m/b on rig 2 with a 850w and a 650w power supply.  On rig 1 I have 7 cards currently until I replace a bad fan on a power supply of mine. That rig has RX570, (4) RX580, RX560 and a GTX 1060 on it. Rig 1 also has a Asus B250 m/b. Stable as can be and making me that $$$. I run 120gb SSD on each.  Rig 2 has two 4gb 2133 memory and Rig 1 has only one stick of 4gb 2133 (until I receive the 2nd ordered 4gb stick of memory).  So far Rig 1 is stable but I just shutdown a 6gpu m/b rig and transferred it all to my 2nd Asus B250 m/b.  You have to have windows 1709 update.

If I could get RX580's direct for $150 each id take 100 of them....for the first order anyway.

I have a 1080 and some 1060's that have dual sockets on them and they all work just fine on the one cable feed split to 8+6 and even an 8+8 on the 1080.

That is fine. Thats why they are made like that for.  I have COrsair HX750 power supplies and have some of the same cables you speak of.  They work fine.

You are confusing the safe rating of the power cable with what im referring to at the socket on the GPU.  Sure the power cable can handle it.  The problem is trying to run all the power thru the 8pin instead of thru the 8 and 6 pin socket on the circuit board.  The heat builds up on the circuit board where socket pins are soldered onto the GPU circuit board.  There are pics on the web of the aftermath of this exact same scenario.

To fix your problem with not enough 8pin outs at your power supply, Simple... They make splitter cables that effectively doubles the amount of 8pin PCIE outputs of your power supply. (Does not double the total output ABILITY of your power supply).  Goto Ebay and use the search term ( PCI-E-6-pin-to-2x-6-2-pin-6-pin-8-pin-Power-Splitter-Cable-PCIE-PCI-Express ) for the cable(s) you need.

 

You are going to have problems with the humidity condensing on the circuit boards of the GPU's.  Not good.  Bringing in humidity with a fan is not a wise idea considering the condensing problem and the fact that it is the humidity that carries heat.  An air conditioner is actually a dehumidifier.  Thats how an a/c unit gets rid of the heat from in your home.  You would be better off with a properly sized window a/c unit exchanging the heat to the outside (via the condenser coil) and it removing the humidity out of the room at the same time.  Sure its another power bill but sure beats a 30gpu replacement bill.

If it has one 8 pin and one 6pin on the GPU, the extra is there for a reason!  To keep the common point for the 12vdc+ and the common point for the 12vdc- on the circuit board from flowing too much current thru the pins that are soldered to the circuit board.  Exceed the rating and it all melts at the circuit board.  But you go ahead and take the short cut over q $5 cable and see what happens.