Some noob questions about multi/single rail switchable PSU (HX1000)

[GregI]

I'm thinking of getting a HX1000. I've looked at unboxing videos and it appears that the default switch position is set to "Multi". This leads me to believe Corsair is happy with this configuration for anyone buying the PSU regardless of what they attach (as long as it's within the wattage ofcourse). Some questions:

1: The power hungry nature of GPUs seems to only be increasing especially with all this talk of the RTX 3000 power spikes. I doubt I'll ever had a GPU that spikes as much as a 3090 but incase I did, would multi rail mode still be fine or is it a case of go against Corsair's default config and switch to single?

2: I take it the correct way of switching between the modes is making sure the PSU power is off at the back and then flipping the multi/single switch? Then waiting afew seconds before switching back on?

3: Noob time. I take it that it doesn't matter what socket I choose to plug the cables into at the back of the PSU for multi rail mode? Just whatever is most convenient like a normal single rail PSU would be?

e.g If I have a GPU with 2 connectors then plugging them into the red sockets would be identical operation to just plugging into 2 neighboring blue sockets?



Thanks

 

[pc-guy]

Just switch it in the software to single rail if you have high powered GPUs unless you want to isolate your PCIE power for different devices for better control and management of power consumption, for single GPU just sue single rail

 

[EsaT]

There are no real multiple 12V rails in any PSU.
Cost and space requirements of actually multiple circuitries make it likely impossible.
What they are is current limited wire groups, which is safety feature.

If you have say 100A max output current it would be often hard for short circuit to have low enough resistance for current to exceed limit for triggering protections.
In case of 12V even just 0.12 ohm total current loop resistance will limit current to 100A.
As result in case of short circuit in end of one wire cable like Molex/SATA PSU would likely have no idea it's pumping current into short circuit and melting cables and connectors.

Having multiple wire groups with individual current limit set lower makes it easier for protections to detect fault situation.
In case of 1kW PSU would see that as sensible for normal user.
But downside is that any big power consumers must be split between multiple wire groups with individually drawn current lower than protection triggering level.
Otherwise normal operation could trigger PSU's shut down.

According to manual max current is 40A.
There's likely some room before actually triggering protection.
But in case of the most power hungry cards wouldn't count that enough for transients.
So would suggest asking Corsair what PCIe cable connectors are under same limit, or is there individual limit for every one.
In the latter case it wouldn't matter which two connectors you would use for PCIe cables.