3 ms·

I think this is backwards. Flash memory programs (writes zeros) faster than it erases (writes ones), and it erases in blocks. So I would expect an empty USB dri

I think this is backwards. Flash memory programs (writes zeros) faster than it erases (writes ones), and it erases in blocks. So I would expect an empty USB drive to be filled with ones, not zeros. Otherwise you would have to erase every "empty" block before the first write.

fwlr 3y ago
I get why writing zeros might be faster than writing ones (easier to discharge than charge) but I don’t see why that would mean an empty flash drive would start with all ones. Wouldn’t the manufacturer set it to all zeros as part of manufacturing it?
- TylerE 3y ago
  Doubt it. They probably have a stock file system image they, well, flash to them. Dd on an industrial scale.
- fatuna 3y ago
  The truth is, there is no fundamental difference between a one and a zero. Flash is either charged or discharged. Physically 'erasing' means setting all the flash to charged and 'writing' means setting (part of) the flash to discharged. If charged means one or zero is a matter of interpretation. Most commonly, charged is considered a one.
- AdamH12113 3y ago
  You have it backwards. Programming means moving electrons (negative charge) into the floating gate of the flash transistor. This negative charge blocks the transistor from turning on, a state which is traditionally called "zero". Erasing means removing the trapped charge, which allows the transistor to turn on ("one"). With differential current sensing you could choose either state to be one or zero. I've only worked on NOR flash, so maybe in NAND flash it's the other way around. Regardless of what you call the states, what makes flash flash (as opposed to EEPROM) is that it's erased in large blocks. So the chips should come out of the factory erased. Whether that means all ones or all zeros is up to the manufacturer.

3 ms·

I think this is backwards. Flash memory programs (writes zeros) faster than it erases (writes ones), and it erases in blocks. So I would expect an empty USB dri

by AdamH12113 3y ago

fwlr 3y ago
I get why writing zeros might be faster than writing ones (easier to discharge than charge) but I don’t see why that would mean an empty flash drive would start with all ones. Wouldn’t the manufacturer set it to all zeros as part of manufacturing it?
- TylerE 3y ago
  Doubt it. They probably have a stock file system image they, well, flash to them. Dd on an industrial scale.
- fatuna 3y ago
  The truth is, there is no fundamental difference between a one and a zero. Flash is either charged or discharged. Physically 'erasing' means setting all the flash to charged and 'writing' means setting (part of) the flash to discharged. If charged means one or zero is a matter of interpretation. Most commonly, charged is considered a one.
- AdamH12113 3y ago
  You have it backwards. Programming means moving electrons (negative charge) into the floating gate of the flash transistor. This negative charge blocks the transistor from turning on, a state which is traditionally called "zero". Erasing means removing the trapped charge, which allows the transistor to turn on ("one"). With differential current sensing you could choose either state to be one or zero. I've only worked on NOR flash, so maybe in NAND flash it's the other way around. Regardless of what you call the states, what makes flash flash (as opposed to EEPROM) is that it's erased in large blocks. So the chips should come out of the factory erased. Whether that means all ones or all zeros is up to the manufacturer.