Tree Borrows

I think the most surprising thing from this article is that microSD cards may not even have a decimal amount of space; while all the hard drives I've encountered have at least that much if not somewhat more, apparently the expectation that a 32GB microSD card be able to store 32,000,000,000 bytes isn't the norm. How do the manufacturers find a way to explain that? It's definitely bordering on fraud at that point.

brudgers•19h ago

from the fine article:

according to the SD Physical Layer Specification, “Card Capacity means the sum of User Area Capacity and Protected Area Capacity”

Which makes sense from a manufacturing perspective...what hardware is required to make the thing?

Also makes sense from a marketing perspective...bigger is better right?

And legally, it's right there in the fine print...that's what "SD" means your honor.

bell-cot•3h ago

If you're surprised by that...stay away from magnetic tape storage. The headline "capacities" of those are usually based on optimistic data compression ratios.

RiverCrochet•49m ago

I am really surprised there isn't a linux command out there that allows you to send low-level CMD's to an MMC controller. I thought mmc-utils did.

> SD cards are divided into sections, called Application Units (or AUs). The Video Speed Classes in particular require certain commands to be issued to it to put the card into Video Speed Class mode and to specify which AU the host will be writing to. The host is then supposed to write only to that AU, in a sequential fashion (skipping over any blocks that are already in use). Once the host has reached the AU, it must issue another command to specify which AU it will be writing to next

This is something I didn't know about SD cards. Does SD card firmware mark blocks as belonging to a specific "Application Unit"? Seems to be some sort of "preallocation" scheme.