Flash drives are sold in base-10 units. Nobody gets to see the base-2 nature of the internals.

Three flash drives I have on hand:

  64 GB:
  Disk /dev/sdi: 60 GiB, 64424509440 bytes, 125829120 sectors
  Units: sectors of 1 * 512 = 512 bytes
  
  32 GB:
  Disk /dev/sdi: 28.9 GiB, 31037849600 bytes, 60620800 sectors
  Units: sectors of 1 * 512 = 512 bytes
  
  8 GB:
  Disk /dev/sdi: 7.2 GiB, 7743995904 bytes, 15124992 sectors
  Units: sectors of 1 * 512 = 512 bytes

Apparently they're just kinda sorta close to what they're sold as, and they're not accurate in base10 or base2.

Thanks for sharing those numbers. Definitely closer in base 10, but not as close as mine were.

The 32 GB one is disturbingly off. 31 GB would have been more honest. If the spare sectors required go up more then they'll have to adjust their marketing numbers and maybe we will see 30 GB, 60 GB, or 120 GB flash drives sold.

Actually, there is little consistency in the advertised size of flash drives.

USB sticks are predominantly sold in base-2 sizes (32, 64, 128 GB etc). In fact, I don't think I've ever seen a 30GB or 100GB usb disk.

How SSD sizes are advertised depends entirely on the manufacturer, and even manufacturers don't use a single base: Samsung's EVO series are advertised in multiples of 10 (250, 500GB), while its PRO series use sizes in multiples of 2 (256, 512GB). Sandisk uses 120 GB, 240 GB sizes. I'm not even sure if all those sizes are supposed to represent base-10 or base-2 prefixes.

But those "32", "64", etc., numbers are times 1,000,000,000 bytes.

That isn't the case with some of the ones that I have on hand. This "128GB" stick is "128GB" as a multiple of 1,069,285,120. Presumably, it's 128GiB less an allocation of spare blocks and the filesystem overhead.

MLC (http://searchsolidstatestorage.techtarget.com/definition/mul..., http://birchtree.me/blog/nand-flash-party/), which is used quite a bit in consumer flash, is base n>2.

Those links claim devices use n=4, 8, 16,... but apart from practicalities, I don't see a reason why n=3, 4, 5,... wouldn't work.

Also, these devices may get produced in power of two sizes units, but they all use error-correcting codes that turn their effective size in something non-power of two.

The memory chips are base 2 capacity, yes.

But in what sense are the flash drives base 2? Their capacity isn't. You have to justify your claims.

> But in what sense are the flash drives base 2?

In the sense that the memory chips inside are base 2 capacity and the sole reason you are seeing less is because the flash control chip just reserves some space.

What's the point of pretending you don't understand someone's comment and asking for clarification?

Fundamentally, address decoders are made to operate with binary inputs. That constrains the scope of what they address to powers of 2. With large capacity storage that becomes less relevant as they are overprovisioned with some redundant capacity, but in reality such devices are implementing Nx2^M storage, not Nx10^M.

Compact Flash, SD, thumb drives are all advertised base 2. SSD are advertised usually base 10 but I've seen some advertised base 2. No consistency. But that's marketing for you.

The number of memory cells will be as they need to be addressable...