The problem is that you are using a PSU which was designed to power 2 enthusiast gaming video cards and are trying to power 4 video cards instead.

Yes, after hacking, splicing, and adapting things, every option you mentioned is possible in various combinations. But safely? That's a much harder question to answer and would need to be answered with wire pinouts, wire gauges ("size"), wire lengths, wire diagrams, specific adapter models, etc. The easiest answer for safe power is to use a PSU designed for the purpose.

Many miners use dual power supplies. You could get another psu to power the risers. That's the easiest way and potentially cheaper than trying to get one big enough to handle all the connections you need.

ipkha
Many miners use dual power supplies. You could get another psu to power the risers. That's the easiest way and potentially cheaper than trying to get one big enough to handle all the connections you need.

I have a couple but wont use it , seen to many fires almost started. Why I just got the ASUS H250 BTC PRO today 3 psu's with no daisy chaining.( I have no intention of going above 8-9 gpu's)

I guess they got abit better I may have been off topic sorry http://www.legitreviews.c...ly-adapter-review_1698

For dual PSU's these work great: http://a.co/5jjNU8c
 
I recall a great writeup about powering risers, but can't find it again.  I recollection was it's okay to use SATA on 1070's and less that are underclocked.  4-pin Molex, if you combine two, can power a 1080ti riser.  Otherwise, use 6-pin, it's always safer.

CHing CHing CHing!

Xantac

ipkha
Many miners use dual power supplies. You could get another psu to power the risers. That's the easiest way and potentially cheaper than trying to get one big enough to handle all the connections you need.

I have a couple but wont use it , seen to many fires almost started. Why I just got the ASUS H250 BTC PRO today 3 psu's with no daisy chaining.( I have no intention of going above 8-9 gpu's)

 
Sir, are you sure it's an ASUS H250 BTC PRO?  I can't find any info about this mobo.  Kindly share some link or photo about it.  Thanks!

There are MANY riser designs that use a MOLEX to power them instead of a PCI-E 6-pin power connector - or you can use the PCI-E ones with a "molex-to-PCI-E 6 pin" adapter.
I use EVGA G2 850 models to power a couple of my 5-card rigs (one of those cards being a 1050/1050ti/HD7750 class card ON the motherboard with no PCI-E power connector) without issues, though I find the Seasonic X-850 and SS-860 models work easier as they have more VGA ports AND more "peripheral" ports (and unlike EVGA, the "CPU" ports on the Seasonic units have the same pinout and are interchangeable with their VGA ports on the PS).
 
YOU DO NOT NEED 2 MOLEX TO POWER A RISER (though it doesn't HURT to do so, if you feed them from the same "molex chain" and you already have dual MOLEX to 6-pin PCI-E adapters on hand).
The MOLEX connector itself is rated to handle over 150 watts - the real limitation is the wiring is usually only sized to handle 120 watts on a Molex chain, but that's STILL plenty for safe power of a riser.
A 1080 ti doesn't pull more than 75 watts from a PCI-E bus - THAT IS AN INHERENT LIMITATION OF THE PCI-E SPECIFICATION - there is no need for an "overpowered" riser on those cards.
 
 I recommend AGAINST the use of risers that use a SATA power connector, as the connector ITSELF is only rated for 54 watts while the PCI-E bus is specified to provide up to 75 watts (a few GPUs have been known to exceed this on peaks) and the riser will use a FEW extra watts to "convert voltages" from the +12VDC feed to it into the other voltages the PCI-E bus provides.
There are many cases of success using those type risers because the card on the riser doesn't draw the full 75 watts that is supposed to be available (especially on cards running at lower-than-factory-spec TDP levels to maximize efficiency) but unless you can measure the draw of YOUR CARD at YOUR USAGE from the PCI-E bus and can guarentee 100% for certain it will always be less than about 50 average watts, it's a significant melt-down and fire risk.
 
I normaly use https://www.newegg.com/Product/Product.aspx?Item=N82E16812423198&ignorebbr=1 risers as I have had ZERO issues out of them so far, and they have both the PCI-E and MOLEX port options like some of the Amazon ones posted above.
 
Power the riser AND the GPU from the same power supply - otherwise you are likely to have issues where one power supply will be trying to supply all of the power to multiple GPUs and the other will be "loafing" due to differences in their output set point on the +12VDC line for each supply.
USB risers IN PARTICULAR (and most powered risers in general) do not "share power" at all with the motherboard, but the GPU itself DOES share power from the PCI-E bus and the PCI-E power connector(s) and depending on the design of the power circuitry on the card it MIGHT use both of those power sources in parallel.
 
 
The ASUS B250 Mining Pro is a good board, if you understand it's limits, and works FINE in 2 or 3 power supply setups - the on-board connectors for the 2'nd and 3'd power supplies are set up as a built-in "add2ps" type setup and do NOT share power between them.
Also, if you are using POWERED risers, don't bother with the on-board MOLEX power connectors - I don't understand why ASUS bothered putting those on the motherboard at all and MISconnecting them can CAUSE issues in a multi-PS setup.
 
For reference, I had up to 5 GTX 1080 ti cards on MY B250 Mining Pro for a while - all powered via those Coboc risers I listed, using a pair of EVGA G2 850 power supplies - with zero issues.
Due to restrictions of my current "in process of getting built" infrastructure, though, I'm planning to retire the board from active use and probably sell it off fairly soon, as it's just not going to work well if at all in a shelf/rack setup designed for 5-6 card rigs.