Apple M5 rumors

[Buntschwalbe]

But yeah as others have said, you don't need the MagSafe 3 cable for charging. It has benefits, being MagSafe for one so it's harder to step on the cable and knock the laptop on the floor. It also means you don't use up a USB port. But all the USB-C ports can be used for charging. In fact, the MagSafe 3 connector uses the same system as USB Power Delivery just without any of the data lanes for USB

I'm wondering, how does apple update the firmware of the magsafe cable without any (usb?) data lanes? is there a different data connection?

 

[casperes1996]

I'm wondering, how does apple update the firmware of the magsafe cable without any (usb?) data lanes? is there a different data connection?

I’m actually not sure in that one. It’s possible there’s something else there or maybe just a very small subset of usb database

 

[diamond.g]

I'm wondering, how does apple update the firmware of the magsafe cable without any (usb?) data lanes? is there a different data connection?

I’m actually not sure in that one. It’s possible there’s something else there or maybe just a very small subset of usb database

According to Wiki the center pin carrys data for the magsafe end itself. Though it does mention that that data line does not go to the charging brick.

 

[mr_roboto]

According to Wiki the center pin carrys data for the magsafe end itself. Though it does mention that that data line does not go to the charging brick.

I think that must be an old wiki with information on Magsafe 1/2. In 1&2, the cable between the Magsafe cable head and the charger brick has just 2 conductors, power and ground. The five pins on the Magsafe 1/2 connector are two power, two ground, and a 1-wire serial interface to an ID chip inside the Magsafe cable head. That chip's only functions are to let the computer know the charger's serial number and capabilities, and allow the computer to turn one of the LEDs (green or orange) on.

In Magsafe 1&2, the computer controls the charger indirectly. The charger defaults to outputting a safe low voltage at low maximum current. What it's looking for is for a computer on the other end to attach a load resistor of a known value for some "long" period of time (probably about a second). Once it sees this indirect signal, it changes into the higher-voltage full power mode. While in full-power, if it sees the load go open circuit, it switches back to the low voltage mode.

This scheme makes the exposed pins in the Magsafe connector safe. By default there's no high voltage present, so it can't injure people or start fires. It also makes the system pretty cheap, because the charger can be fairly dumb and the one and only chip in the cable is basically just a ROM that the computer can read.

Magsafe 3 is quite different, because now there's USB-C Power Delivery involved, at least in the middle. The charger is a standard USB-C PD power source, and Apple provides you with a USB-C to Magsafe 3 cable. That cable has to be an e-Marker Type C cable in order to support high power USB-C modes. A youtube channel did a teardown of this cable a while back:



These cables look quite complex. Both the USB-C and Magsafe connector backshells contain fairly complex active circuitry, and there are data wires in the cable, not just power and ground.

On a few occasions (including just now) I've tried searching to find out whether anyone's reverse engineered the signal connections in the Magsafe 3 cable, but I've never found anything. However, I think it's possible (and maybe even likely) that Apple enabled PD handshaking all the way to the computer. If they'd kept the Magsafe 3 connector the same as before (2 power, 2 ground, 1-wire serial, use of sense resistor to turn the power supply on) there'd be no need to have data wires in the cable, and the circuitry in the Magsafe backshell would be simpler.