Editing Disk density (section)

== 5¼-inch media <span class="anchor" id="QD"></span><span class="anchor" id="HD"></span>==
''SD'' (''1D'') and ''DD'' (''2D'') designations were generally identical to those of 8-inch disks.

''Quad density'' (QD or 4D<!-- BASF -->) doubles capacity over DD by narrowing the width of tracks to {{convert|0.160|mm|abbr=on}} for a density of 96&nbsp;tpi. Some manufacturers ([[Micropolis (company)|Micropolis]], [[Tandon]], [[Micro Peripherals]] (MPI), [[Teac]]) used a track density of 100 tpi for quad-density drives, which were incompatible with 96 tpi models.

The [[Commodore 8050]] and [[Commodore 8250|8250]] are rare instances of drives that used 375&nbsp;kbit/s GCR code instead of the usual 250&nbsp;kbit/s double-density format and they could store roughly 500 kilobytes on one side of a disk.

''High density'' (HD) improves capacity by utilizing a 96&nbsp;tpi track density in conjunction with improved cobalt disk coating and stronger 600-oersted write heads, allowing 9,646 bpi to be written.