[nicebill8]

> All Mac portables with the Apple T2 Security Chip feature a hardware disconnect that ensures the microphone is disabled whenever the lid is closed.

vs.

> On the 13-inch MacBook Pro and MacBook Air computers with the T2 chip, and on the 15-inch MacBook Pro portables from 2019 or later, this disconnect is implemented in hardware alone.

Do these statements not contradict each other for the 15" 2018 MacBook Pro, for example, which includes a T2 chip? This would also contradict earlier documentation provided on the T2 chip by Apple themselves [1].

From [1]:

> All Mac portables with the Apple T2 Security Chip feature a hardware disconnect that ensures that the microphone is disabled whenever the lid is closed. This disconnect is implemented in hardware alone, and therefore prevents any software, even with root or kernel privileges in macOS, and even the software on the T2 chip, from engaging the microphone when the lid is closed.

[1] https://www.apple.com/euro/mac/shared/docs/Apple_T2_Security... (October 2018, page 13)

[alias_neo]

I don't think they contradict each other. The way I read it is, the former, have hardware disconnects controlled by some software/firmware, such as a relay/MOSFET or something of that kind; an electronic switch.

The latter I read as being hardware _only_; "only" being the key addition to this sentence. I would expect this implementation to be something like a reed switch to magnetically disconnect the lines _physically_ rather than electronically.

[ken]

Isn't the whole point of software to control hardware, at some level? How is hardware-controlled-by-software different from plain old software-controlled? If a switch can be closed by software, I'm having trouble putting my finger on exactly what security benefit that might offer.

[hamiltonkibbe]

I don't think the distinction is a FET vs a reed switch -- the means of blocking electrons, rather, it's in what decides whether that switch is open or closed. I would consider a circuit like this driving the FET/relay/etc. to be a "hardware disconnect" (using HDL to describe the circuit, not suggesting it should be programmable logic):

  module mic_enable (lid_closed, lots, of, signals, mic_enable);
    input lid_closed, lots, of, signals;
    output mic_enable;
    assign mic_enable = !lid_closed & lots & of & other & signals;
  endmodule