Summary of the Buildzoid video courtesy of redditors in r/hardware:
> TL;DW: The 3090 had 3 shunt resistors set up in a way which distributed the power load evenly among the 6 power-bearing conductors. That's why there were no reports of melted 3090s. The 4090/5090 modified the engineering for whatever reason, perhaps to save on manufacturing costs, and the shunt resistors no longer distribute the power load. Therefore, it's possible for 1 conductor to bear way more power than the rest, and that's how it melts.
> The only reason why the problem was considered "fixed" (not really, it wasn't) on the 4090 is that apparently in order to skew the load so much to generate enough heat to melt the connector you'd need for the plug to not be properly seated. However with 600W, as seen on der8auer video, all it takes is one single cable or two making a bit better contact than the rest to take up all the load and, as measured by him, reach 23A.
- Most 12VHPWR connectors are rated to 9.5-10A per pin. 600W / 12V / 6 pin pairs = 8.33A. Spec requires 10% safety factor - 9.17A.
- 12VHPWR connectors are compatible with 18ga or at best 16ga cables. For 90C rated single core copper wires I've seen max allowed amperages of at most 14A for 18ga and 18A for 16ga. Less in most sources.. Near the connectors those wires are so close they can't be considered single core for purpose of heat dissipation..
Honestly with 50A of current we should be using connectors that screw into place firmly and have a single wipe or a single solid conductor pin style. Multi-pin connectors will always inherently have issues with imbalance of power delivery. With extremely slim engineering margins this is basically asking for disaster. I stand by what I've said elsewhere: If I was an insurance company I'd issue a notice that fires caused by this connector will not be covered by any issued policy as it does not satisfy reasonable engineering margins.
edit: replaced power with current... we're talking amps not watts
I was wondering if this was a thing - in RC quads and the like we use these massive bullet connectors (XT30/60/90 and similar) which often have lower resistances than the wires themselves.
Yeah, they take soldering for the wire/connector interface, but presumably there are connectors similarly designed with crimp terminals, or it's just something the mfgs will have to deal with.
> TL;DW: The 3090 had 3 shunt resistors set up in a way which distributed the power load evenly among the 6 power-bearing conductors. That's why there were no reports of melted 3090s. The 4090/5090 modified the engineering for whatever reason, perhaps to save on manufacturing costs, and the shunt resistors no longer distribute the power load. Therefore, it's possible for 1 conductor to bear way more power than the rest, and that's how it melts.
> The only reason why the problem was considered "fixed" (not really, it wasn't) on the 4090 is that apparently in order to skew the load so much to generate enough heat to melt the connector you'd need for the plug to not be properly seated. However with 600W, as seen on der8auer video, all it takes is one single cable or two making a bit better contact than the rest to take up all the load and, as measured by him, reach 23A.
https://old.reddit.com/r/hardware/comments/1imyzgq/how_nvidi...