How do USB flash drives hold so much data?

We might take them for granted, but advances in chip technology have given us miniature libraries that fit in our pockets.

31st October 2012
How do USB flash drives hold so much data? (Getty)

Asked by: Ron Clarke, Hereford

Flash storage devices are based on chip technology called Electronically Erasable Programmable Read Only Memory (EEPROM). USB flash sticks use a refined version of EEPROM. In its earliest incarnation, individual bits of data on the chip had to be erased separately. It was like a vertically stacked library where getting at one book at the bottom of a pile meant having to move the books above it one at a time.

But now multiple memory cells can be addressed simultaneously, allowing entire blocks to be written and rewritten in one go, like moving a pile of books, rather than one book, at a time. It requires considerable on-chip processing and is a feat that has come about through recent advances in chip design and miniaturisation, ushering in USB drives capable of storing gigabytes of data.

Read more:


SFQASubscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun facts.