It might be that the workaround to NVidia connector problems is exactly the opposite of what people are recommending, and short, high quality cables are bad for 4090/5090. As discussed in other threads, the problem with 4090/5090 happens because the wires are supposed to carry large current in parallel, but the contact resistance can vary significantly, resulting in uneven current distribution in the wires.
This effect is greater for short, high quality cables, which is what the MODDIY cable was: good thick wires with gold plated contacts.
To see why, consider a short cable, 1 foot in length (30cm), using 16 gauge wires. The individual wire resistance is 0.004 Ohms. The contact resistance can vary between 0.006 Ohms to say 0.016 Ohms.
Then, the maximum variation between good and bad is (2*0.06+0.004) to (2*0.006+0.004) which is a factor of 7.75. A current difference of a factor of 7.75 results in a power dissipation difference of a factor 60 - meltdown.
Now, suppose you are using a similar cable, but 3 feet in length (1m), with the same 16 gauge wires. Then, the individual wire resistance is 0.018 Ohms, and the ratio between good and bad contacts is at most (2*0.06+0.012)/(2*0.006+0.012)=5.55
If the same 3 feet cable was made using cheaper 18 gauge wires, then ratio between good and bad contacts is at most (2*0.06+0.019)/(2*0.006+0.019)=4.48. For 20 gauge wires, we get (2*0.06+0.030)/(2*0.006+0.030)=3.57.
To summarize, the wire resistance acts to buffer the difference in contact resistance and balance the current. Longer cables with thinner wires will have less variation in resistance for each individual power lane compared to short cables with thicker wires.
We can't go too low in wire gauge because 20 gauge is already questionable, even for chassis wiring, if you include the possible factor of 3.57 current spike:
Using wires with higher-temperature insulation (like PTFE) will allow for the use of thinner wire with higher resistance.
There should be similar effect for contact plating: gold-plated contact should be able to achieve lower resistance per contact and higher current spike compared to nickel or tin-plated ones, but I don't know by how much.
Of course, a better long-term solution is an improved connector:
www.techpowerup.com
This effect is greater for short, high quality cables, which is what the MODDIY cable was: good thick wires with gold plated contacts.
To see why, consider a short cable, 1 foot in length (30cm), using 16 gauge wires. The individual wire resistance is 0.004 Ohms. The contact resistance can vary between 0.006 Ohms to say 0.016 Ohms.
Then, the maximum variation between good and bad is (2*0.06+0.004) to (2*0.006+0.004) which is a factor of 7.75. A current difference of a factor of 7.75 results in a power dissipation difference of a factor 60 - meltdown.
Now, suppose you are using a similar cable, but 3 feet in length (1m), with the same 16 gauge wires. Then, the individual wire resistance is 0.018 Ohms, and the ratio between good and bad contacts is at most (2*0.06+0.012)/(2*0.006+0.012)=5.55
If the same 3 feet cable was made using cheaper 18 gauge wires, then ratio between good and bad contacts is at most (2*0.06+0.019)/(2*0.006+0.019)=4.48. For 20 gauge wires, we get (2*0.06+0.030)/(2*0.006+0.030)=3.57.
To summarize, the wire resistance acts to buffer the difference in contact resistance and balance the current. Longer cables with thinner wires will have less variation in resistance for each individual power lane compared to short cables with thicker wires.
We can't go too low in wire gauge because 20 gauge is already questionable, even for chassis wiring, if you include the possible factor of 3.57 current spike:
American Wire Gauge Chart and AWG Electrical Current Load Limits table with ampacities, wire sizes, skin depth frequencies and wire breaking strength
AWG Wire size chart and ampacity table for design engineers including skin depth frequencies and tensile strength data; electrical cable size
www.powerstream.com
Using wires with higher-temperature insulation (like PTFE) will allow for the use of thinner wire with higher resistance.
There should be similar effect for contact plating: gold-plated contact should be able to achieve lower resistance per contact and higher current spike compared to nickel or tin-plated ones, but I don't know by how much.
Of course, a better long-term solution is an improved connector:
![www.techpowerup.com](https://tpucdn.com/forums/data/assets/logo/logo-og-v1.png)
Proposed new Power Connector
With all the attention on melting graphics card connectors, this might be an opportunity to switch manufacturers to a connector that we like. Here is my proposal - please comment whether you like the idea or not, any changes and if we get enough people behind it we'll try to make them listen...
![www.techpowerup.com](https://tpucdn.com/forums/data/assets/logo/icon-192-v1.png)