mZuzek said:
I'm pretty sure it's not really a lie. There's a reason why the SD cards never give you as much space as advertised, but it's a technicality I don't really understand either, I just accept it. But yeah, there is no SD card in the world that's going to give you as much storage as it says on the box, they only ever come somewhat close to it. |
First of all, I found on Amazon plenty of real knockoffs and fakes. If you get a 512GB SD-card for 20 Euro (so maybe around 25 Dollar) you should not trust in it. It is very easy to produce a card that has about 100MB or so but the controller advertises 500 GB (so that is shown in the Operation System), but in reality saves your stuff over and over in the memory.
But what you talk about are the prefixes. SI defines prefixes like Kilo ( k ), Mega (M) and so on. But Byte is no SI-unit. So in early computing the SI-prefixes were used, but instead of 1000 for Kilo for instance, it uses the power of two that is close, namely 1024. To avoid confusion, the IEC (International Electrotechnical Commission) proposed to add a bi to the first syllable of the prefix-name (for binary), so Kibibyte (KiB) or Mebibyte (MiB). Anyways, if operation systems show you MB or GB, they usually mean MiB or GiB. But producers of mass storage quickly realized they aren't technical lying, if the use MB and GB as SI defined it. The difference can be quite big.
| SI unit | value | difference | IEC-unit | value |
| Kilobyte (kB) | 1000 (10³) | 2.4% | Kibibyte (KiB) | 1024 (210) |
| Megabyte (MB) | 1,000,000 (10⁶) | 4.9% | Mebibyte (MiB) | 1,048,576 (220) |
| Gigabyte (GB) | 1,000,000,000 (10⁹) | 7.4% | Gibibyte (GiB) | 1,073,741,824 (230) |
| Terabyte (TB) | 1,000,000,000,000 (10¹²) | 10% | Tebibyte (TiB) | 1,099,511,627,776 (240) |
The left is what companies use to advertise, the right what your operation system usually shows. So 400GB advertised are shown in operation systems as 372.5 GiB.
Last edited by Mnementh - on 11 August 2019
