How to safely connect ATX power supplies?

Question

Iron

There is a lot of conflicting information on the internet, so here it is!
There are two GOLDEN TIGER power supplies.
You need to power the board "SABERTOOTH 990FX R2.0" with 4xPCI-E + R9 270X Dual-x + HDD
Then I will add more radeons (just for games;). One BP is clearly not enough.
The PSU sticker says:
+3.3v=13A
+5V=16A
+12V1=14A
+12V2=16A
-12V=0.5A
+5VSB=2.5A
+5v & +3.3V COMBINED LOAD 123W
+5v & +3.3V & +12V COMBINED LOAD 483W
450W REAL TOTAL OUTPUT IS 500W MAX
Big letters: SWITCHING POWER SUPPLY
CAUSTION:
DO NOT REMOVE THIS COVER
Absolutely all the wires inside, connected together by voltage.
I was surprised that +12V1=14A and +12V2=16A are soldered together!
Separately, only wires: PSON - green, 5VSB - lilac, PG - gray and 3.3vs - brown.
Each PSU is 500W - although the inscription "450W REAL TOTAL OUTPUT IS 500W MAX" inspires some uncertainty.
Is it possible?
0. Combine the power supply of both 220v units (including ground) and GND (black) at the output, and PSON?
1. Will it work?
2. What will happen at the outputs when both PSUs start not quite synchronously or / and on one, for example, 5.03, and on the other 4.99 volts?
3. Two PSUs "450W REAL TOTAL OUTPUT IS 500W MAX" will give "900W REAL TOTAL OUTPUT IS 1000W MAX"?
4. SWITCHING POWER SUPPLY - just takes up space here, as well as on the PSU sticker.
Thanks in advance for your reply!

Answer 1

In short - listen to the tips above and take one high-quality (not unnamed Golden Tiger) power supply with sufficient power. It seems to me that a decent block of 800 watts is enough for you.
0. Yes, you can merge, but it's not worth it
1. Yes, but you risk iron.
2. Voltage equalization currents will walk, which threaten your hardware.
3. No
The topic was dealt with many times on the overclockers.ru forum when there were no decent high-power PSUs. Read. It would be possible to power different pieces of iron - a video card, HDD from one PSU, the mother - from another. But I would not do this with questionable PSUs.

Answer 2

You don't need to combine them. This won't end well.
You can power different circuits with these PSUs, as a last resort.
Yes, of course it's better to buy "1BP at the price of X * 3", if you are satisfied with its characteristics.

Answer 3

I tried this, but on old hardware, just for the sake of experimentation, PSUs work quite well in pairs. I connected the ground and the power wire, one PSU fed the motherboard, the other screws, fans, etc. I think it's not worth the risk of new hardware, buy a powerful, branded PSU, replacing the motherboard and video card is more expensive.

Answer 4

Here's how I connected https://www.youtube.com/watch?v=TF9zFJsS0-k