Classic Computer Magazine Archive COMPUTE! ISSUE 80 / JANUARY 1987 / PAGE 10

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Double Or Dual?
I have heard that the 1571 is a double-sided disk drive. Does this mean it is like a dual drive? Does it need doublesided disks?
Eddy Belew

A single-sided drive such as the 1541 has one read/write head, so it accesses only one side of a disk (it reads and writes the bottom side of the disk). The 1571 is a double-sided drive; it has two read/write heads, so it can write to both sides of a disk. To maintain compatibility, the structure of the 1571's directory is similar to the 1541's, and the 1571 fills up the bottom side before it goes to the top of the disk.
    But both the 1541 and 1571 can hold only one disk at a time, so both are singledrive units. A dual drive has two drive mechanisms and can hold two disks at the same time (this is not the same as two single drives). A dual drive may be singlesided or double-sided. Commodore has not manufactured a dual drive for some time. However, they are common on MSDOS computers (the IBM PC and compatibles).
    Thus, the 1571 is not a dual drive. At one time Commodore announced plans for a dual double-sided drive (named the 1572), but the' plans were apparently dropped.
    If you should buy a 1571, we recommend using double-sided (DS) disks. Single-sided disks (which usually have SS on the label) are tested and certified for one side only. You may find that single-sided disks work in the 1571, but you can't know when the second side might fail. It's safer to stick with DS disks.
    The Atari ST also uses both singlesided and double-sided disks. The 1040ST has one built-in double-sided drive. External floppy drives can be either singlesided or double-sided. Atari seems to be phasing out single-sided drives in favor of double-sided drives, since a double-sided ST drive can read and write to singlesided ST disks without any problems. However, since there are many singlesided drives still in use, virtually all commercial ST software is provided on singlesided disks. We have yet to see a dual drive for the ST.