How two volunteers built the Raspberry Pi’s operating system | Ars Technica:
When Thompson and Green got started, the Pi wasn't actually available yet. Even if it had been, it wouldn't be capable of rebuilding Debian in a reasonable amount of time.
Thus, Thompson set up a cluster of eight Freescale iMX53 Quick Start Boards, each with 1GB of memory, a 1GHz ARMv7 processor, and (most importantly) SATA hard drives. One of the main reasons the Pi would be unsuitable for this type of work is the bottleneck introduced by USB storage, Thompson said. The Freescale boards were able to build Raspbian anywhere from four to 12 times faster than the Raspberry Pi would have.