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Apple designed their product to isolate damage to just the USB circuitry, whereas the bad cable seemingly tookout the entire Chromebooo laptop.
by coin 11y ago
Apple designed their product to isolate damage to just the USB circuitry, whereas the bad cable seemingly tookout the entire Chromebooo laptop.
- NeutronBoy 11y ago> Benson Leung, a Google engineer, and Dieter Bohn, executive editor at The Verge, wound up frying their notebooks after plugging in USB cables they bought at Amazon. Leung's laptop, a Chromebook Pixel, wouldn't boot afterward. Bohn told me his notebook, a MacBook Air, no longer has working USB ports.
- Shog9 11y agoYeah, and who needs USB on a MacBook? Seriously though, why would you assume this? The article doesn't state it - it gives examples of both devices being damaged in different ways, but cites only Dell as actually designing their hardware to tolerate bad cabling. Perhaps Apple has built in some mechanism to protect the rest of the circuitry from a USB failure, but without further information it's more reasonable to assume that the MacBook owner just got (comparatively) lucky here. Years ago, I shorted out a USB port on a desktop PC, with the same results - system booted and worked just fine, except the USB port was dead. Upon opening the box, I found a popped cap and some scorching on the motherboard; I'd be... reluctant to call this a well-designed failure mode.
- makomk 11y agoNone of the protection features that Dell claimed to have would've protected against what killed the Chromebook: a cable wired up to feed a negative voltage into the charging port. The author of this article is so terminally confused that he couldn't even ask about the right things
- smbarber 11y agoThe failure modes are completely different. The MacBook went overcurrent when a bad cable told an attached phone it could draw more current than it should. Detecting overcurrent due to a badly behaved device or a short in the cable is fairly common. The cable attached to the Chromebook was totally miswired and flipped Vbus and ground, supplying -5V where 5V was expected. As the article said, nothing is really designed to handle this kind of failure because it should be blatantly obvious to the cable manufacturer if there were any sort of quality control.
- X-Cubed 11y agoThat's not entirely true. Reverse polarity protection is very common, and often only requires a single diode in series with the +V line, so that current can only flow in one direction.
- marshray 11y agoA diode will drop about 0.5-0.6 volts, which could eat 10% of your energy, so reverse polarity protection is usually used in devices where someone could plausibly install the batteries backwards. I think it's probably rare on something on a highly controlled standard connector like USB.
- rrmm 11y agoIt's fairly easy to do it without the diode drop if you use a mosfet, but you do incur the cost of a more expensive part.
- yardie 11y agoIt's usually common in low voltage, low current devices. I have a massive inverter charger on our boat that has in giant letters "NO REVERSE POLARITY PROTECTION". It typically handles up to 200amps at 12V.