Tell me a little about your MDS please

There was an option Intel sold that upgraded the internal 801 drive to work in a double-density mode. That included a two-board multibus set that could control up to four drives. Normally that two-board set controlled up to two external two-drive packages. So up to four double-density single-sided drives total. They also sold a special cable that allowed that internal two-board-set to control the one internal drive. That cable went from the interface board of the two-board set to two connectors. One connector is the 50-pin edge to the 801 drive directly. The other connector is a 37-pin D-type connector that attaches to the back panel of the MDS and is for controlling a two-drive external box. There are other permutations, but that is the most common way to get the internal drive to be double-density.