Hacked up a little setup to get some numbers to replace speculation about Naomi power consumption, how much the DIMM uses etc.
https://wiki.arcadeotaku.com/w/PCB_Power_Consumption
I was a little surprised to see that the most heavily used rail is 3.3V.
Naomi with cart uses 2.4A @ 3.3V, which is manageable - but with netDimm it jumped to 4.3A which is enough that width and length of cables come into play.
I didn't have the correct cables to add GD-ROM drive on top of all this, but GD-ROM is pretty obsolete anyway.
Also, both games were not encrypted - it could be that encrypted games use more power, but I have a feeling they don't.
Executive summary: the netDimm does indeed draw a fair bit of current.
https://wiki.arcadeotaku.com/w/PCB_Power_Consumption
I was a little surprised to see that the most heavily used rail is 3.3V.
Naomi with cart uses 2.4A @ 3.3V, which is manageable - but with netDimm it jumped to 4.3A which is enough that width and length of cables come into play.
I didn't have the correct cables to add GD-ROM drive on top of all this, but GD-ROM is pretty obsolete anyway.
Also, both games were not encrypted - it could be that encrypted games use more power, but I have a feeling they don't.
Executive summary: the netDimm does indeed draw a fair bit of current.