Both iPhone and Watch ship with a Secure Enclave processor. Both are alsoH11-class SoCs. As such, there are broad similarities between the different blocks.Embedded cores present on-die use firmware written withRTKit, which is Apple's own broadly-used RTOS on cores codenamedChinook.The codename for the eSIM platform on both the iPhone and Watch isVinyl.The NFC (+Apple Pay?) controller is namedStockholm, and the Apple Watch Series 4 + iPhone Xs and Xr ship with version 5.

TSMC is the foundry used exclusively for all the new SoCs this year, using their 7nm mobile process.

Apple WatchSeries 4 (S4: T8006) uses twoTempest cores as the AP. The ILP32 ARMv8 ABI is used, making possible to use ARMv8 instructions with lower memory pressure. The GPU is Apple G11M. The arm64_32 ABI is used, to be able to recompile LLVM bitcode from older Watches to S4 without action from the developer.On cellular modem-equipped variants, Intel'sIBIS modem is used, which isn't referenced anywhere publicly, except a post onthelayoff. It runs on an Arm core.The neural engine is codenamedMercury.

Apple M9 is the WiFi and Bluetooth controller, codenamedMarconi. The WiFi PHY has theTesla codename. The firmware is ran on ARM Cortex-R5 cores with software floating-point.

Apple A12 (T8020) uses twoVortex and fourTempest cores as the AP. Thearm64e ABI is used, which adds support for pointer authentication. The video engine has thePanda codename. The GPU is Apple G11P.

Intel'sICE baseband is used (XMM7560, flashless configuration), which has a pair of Intel Atom cores at 1.2GHz (?).

The neural engine is codenamedQuin and the ISP is namedPetra.A Lattice FPGA driving a small block calledMaggie is present.

iPad Pro 2018 uses the Apple A12X (T8027), which has 4 big cores and 4 little cores. The neural engine is namedPontus.Maggie isnot present. The GPU is Apple G11G.

https://www.thelayoff.com/t/LUMrIcz An employee rant, but unfortunately the only place where the IBIS modem is referenced anywhere on the public Internet.

https://twitter.com/esizkur/status/1040899693524516864 on VMX being present but unused apart from a switch to VMX non-root at bootup.