5 ms·
"Replacing a tiny part" is trivializing the work necessary to do this, in my opinion. eMMC flash is typically a ball-grid array part and it's soldered down har
by joezydeco 7y ago
"Replacing a tiny part" is trivializing the work necessary to do this, in my opinion.
eMMC flash is typically a ball-grid array part and it's soldered down hard to the motherboard of the processor. Almost every mobile device has the same setup and it's tricky and expensive to rework this chip.
You need to carefully desolder it off the board, reball the part with the correct masking stencil, then reapply it without torching the rest of the board, missing a solder connection, or zapping any other component with static electricity.
You can see a similar process done on an iPhone here: https://www.youtube.com/watch?v=y4M9uAZlbK4 https://www.youtube.com/watch?v=y4M9uAZlbK4
You can understand why Tesla would rather replace/refurbish the board than try to field-repair it.
- Crosseye_Jack 7y agoThey have been replacing the whole media unit including the screen (and charging customers $2k-5k for the priv) where they could replace the processor module board (which is "just" a add-in board inside the media unit) keeping the rest of the media unit and lowering costs. Sure refurbish the processor module and replace the eMMC at a proper rework station but replacing the whole media unit esp when the failed part is on a removable board just seems like a huge waste to me esp when the customer is footing the bill.
- raverbashing 7y agoThis is the right answer Replace the board, then you can refurbish it in a specialized lab Same reason why genius bars won't replace components, just boards
- solarkraft 7y agoLuckily Tesla isn't very space or money limited with this pretty ciritcal component. An SD card would make life easier for everyone, as the logs could be easily read out and the booting OS changed - yay for actually owning the device you paid for. But wait: That's not something Tesla wants.
- joezydeco 7y agoeMMC is literally the equivalent of an SD card soldered down to the PCB. It’s more mechanically stable and also way faster. In my experience, removable SD wouldn’t hold up to an application like this.
- Crosseye_Jack 7y agoThe actual logs Tesla seem interested in (including the stills of things they are interested in) get written to a removable SD Card before getting uploaded to the Tesla mother-ship. You are not wrong that a soldered eMMC (compared to a eMMC held by a ZIF or a removable SD Card) would be more mechanically stable and potentially faster (A fast uhs-ii sd card compared to a cheap slower eMMC for example), just saying that Tesla already use removable SD cards in production cars today (which doesn't brick your media unit if it dies or dislodges). Storing the OS on a removable SD Card is (imo) a bad idea, but if they are really interested in these logs they already have a easier to replace removable storage "drive" they could write the logs to instead of burning up the eMMC.
- naikrovek 7y agoAn SD card might work fine if it is mounted properly. The slot found on a Raspberry Pi would not at all be sufficient. If it were held in and held against some robust contact pins it likely would be fine, even under automotive conditions. There are SIM card slots that are used on heavy vehicle computers and controllers (the ones that run the engine and so on) that are robust enough to hold a SIM card in place for years of excessive daily vibration.
- londons_explore 7y agoWhenever I drop my phone I see the "SimProcessor" service spinning up... I suspect that designing reliable spring contacts isn't as easy as it seems...
- naikrovek 7y agoYeah, phones aren't designed to have robust SIM slots, they're designed to be thin, so they use very low profile SIM cradles that are not robust to impact. The trade-offs for a high vibration environment are very different.
- arcticbull 7y agoIt feels like they should just turn off syslog in production builds, release it in a firmware update and offer a recall for everyone affected by broken board.
- pbreit 7y agoSo it's not fixable with software update?
- Crosseye_Jack 7y agoThe under lying issue can not be fixed with software. the eMMC is simply running out of write cycles. BUT they can mitigate the issue by not writing the syslog to the eMMC allowing the remaining write cycles to last much longer (This change could be done with a software update). On the newer versions of the Media Unit instead of disabling writing the syslog to the eMMC they added more storage to the processor boards which isn't going to solve the problem just push it from appearing to further down the road.
- naikrovek 7y agoThe problem is that there is significant write amplification as the used space on the partition approaches the total space of the partition. To say that the choice to use eMMC is the fault is to say that ANY use of flash storage is a faulty decision. If there is sufficient space on the drive to mitigate write amplification, then the media will last a very long time indeed. Longer than the drivetrain, certainly. The problem is that Tesla doesn't delete logs it has collected from the cars. All Tesla vehicles (as I understand it) upload their logs more or less continually. Currently, the firmware on the cars doesn't delete those logs once they've been uploaded, presumably so that they're available when it is time to service the vehicle. The disk filling up due to bad log file hygiene, coupled with the fact that the storage is flash-based, together cause the issue.
- londons_explore 7y agoMost eMMC cards use really primitive wear levelling algorithms. A simple firmware update to the eMMC chip could make it use a wear levelling algorithm that really does spread writes evenly over the whole chip. Current implementations simply use a sector till it goes bad and then using a spare till that goes bad, etc. After 1% or so go bad, the whole device rejects writes entirely. With a decent implementation (like ssd's mostly do), you will never be able to kill a card in a lifetime.
- deleted 7y ago[deleted]