The iOS 26.3 release candidate includes references to a pair of unreleased chips that are in the M5 family, according to information found by Nicolás Alvarez and shared with MacRumors.
The iOS 26.3 RC mentions two unreleased SoCs, T6051 and T6052, with associated H17C and H17D platform names. The 17 is a reference to the M5, as the standard M5 chip is numbered H17G. Typically, the "C" lettering is used with a Max chip, and the "D" lettering is used for Ultra chips. G is used for standard chips, and S is used for Pro chips.
When using Apple's past numbering and lettering as a reference, that would suggest an M5 Max and an M5 Ultra chip. There is no current reference to T6050 H17S, which is the chip identifier and platform name we'd expect for the M5 Pro.
Since we're currently waiting on new versions of the MacBook Pro with M5 Pro and M5 Max chips, the chip references located are a bit confusing. We have three possibilities: there's an M5 Pro chip along with an M5 Max and M5 Ultra chip and it's just not added to the iOS 26.3 code yet, Apple is changing its numbering, or Apple is planning for M5 Max and M5 Ultra MacBook Pro models.
- Chip 1 in the beta: T6051, H17C. Presumably M5 Max.
- Chip 2 in the beta: T6052, H17D. Presumably M5 Ultra.
- Not in the beta: T6050, H17S. Chip identifier expected for M5 Pro.
Apple's past Max chips have all used "C" lettering, including the M1 Max (H13C), M2 Max (H14C), M3 Max (H15C/H15M), and M4 Max (H16C). There was also an M variant of the M3 Max for the 14-core chip, with Apple using C for the 16-core chip.
Ultra chips have all used "D" lettering, including the M1 Ultra (H13D), M2 Ultra (H14D), and M3 Ultra (H15D). There was no M4 Ultra chip.
It's not clear why we are only seeing signs of an M5 Max and M5 Ultra chip, but rumors suggest that new MacBook Pro models with higher-end M5 chips are set to launch in the next few weeks. Apple is supposedly working on a Mac Studio in the M5 family, which would use an M5 Ultra chip, but we haven't heard rumors about an upcoming launch.
