Re: 3-4 years??
...If this is such an issue then the eMMC should be an easily replaceable part, e.g. an SD card under the dash...
Yup, that would make sense. ISTR seeing Rich Rebuilds showing a previous issue where the flash would just fill up with log files and fail, which was fixable via an OTA update. I agree that it would make sense for wear parts to be easily accessable, and replaceable. So rather than having to replace an entire ECU/MCU due to being SOC, just replace the drive.
I guess that's part of the cost modelling done by the mature automakers, ie labour cost to get to a part, then cost of just swapping a module vs swapping a component. Would seem kinda important, especially if done under warranty. And I guess given Teslas are mobile compute devices, there may be some benefits to swapping the entire 'brain' with the latest tech so it could support new features.
Biting the hand that feeds IT
