So I’m doing some testing of USB-C cables using a tester and a constant load (I’ll have another post soon with some questions on this). But before running each test, I’m checking the E-mark chip and then enumerating the charge capabilities of each to see what they report being capable of.

I’ll use 3 different brands of cables as samples of my question. Power Supply (PS) 1 is an Anker 100W with PPS support. PS2 is a MacBook Pro 94W brick with no PPS support.

• Cable A
  • Emark: 20V@5A USB3.2 Gen 2
  • Max PD using PS1: PD3.0 PPS 29W
  • Max PD using PS2: PD2.0 94W
• Cable B
  • Emark: 20V@5A USB3.2 Gen 2
  • Max PD using PS1: PD3.0 PPS 100W
  • Max PD using PS2: Not tested
• Cable C
  • Emark: 50V@5A USB2.0
  • Max PD using PS1: PD3.0 PPS 29W
  • Max PD using PS2: PD2.0 94W

So the question: What would be limiting Cables A and C to PPS 29W?