https://en.wikipedia.org/wiki/Rainbow_100 https://en.wikipedia.org/wiki/Rainbow_100 The floppy disk drives, known as the RX50, accepted proprietary 400 kB sing

https://en.wikipedia.org/wiki/Rainbow_100 https://en.wikipedia.org/wiki/Rainbow_100 The floppy disk drives, known as the RX50, accepted proprietary 400 kB single-sided, quad-density 5¼-inch diskettes. Initial versions of the operating systems on the Rainbow did not allow for low-level formatting, requiring users to purchase RX50 media from Digital Equipment Corporation. The high cost of media ($5 per disk) led to accusations of vendor "lock-in" against Digital. However, later versions of MS-DOS and CP/M allowed formatting of diskettes. Of note was the single motor used to drive both disk drives via a common spindle, which were arranged one on top of the other. That meant that one disk went underneath the first but inserted upside-down. This earned the diskette drive the nickname "toaster". The unusual orientation confused many first-time users, who would complain that the machine would not read the disk.