from the media. Winchester technology allowed the head to land and take off from the disk media as the disk spun up and down. This resulted in very significant savings and a large reduction of complexity of the head and arm actuating mechanism. This head design rapidly became a standard design within the disk drive manufacturing community. Up into the early 1990s the term Winchester or Winnie was used for hard disk drives in general long after the introduction of the 3340, but is no longer in common use in most parts of the world. IBM 3344 The IBM 3344 is similar to the 3340, except that it uses fixed media rather than removable 3348 data modules, each spindle has 4 logical drives each with the capacity of a 3348–70, there is no A (head of string) model and it is only available in dual drive models. The 3344-B2F is identical to the 3344-B2 except that both drives have fixed heads over some cylinders. Both 3344-B2 and 3344-B2F require a 3340-A2 or 3340-A2F as head of string. IBM 3350 The IBM 3350 Direct Access Storage Facility, code-named Madrid, was introduced in 1975 for use with IBM System/370. Its non-removable head-disk assemblies (HDAs) are sealed and included the head and arm assembly. The 3350 disk geometry is 555 cylinders, 30 heads, and 19,069 bytes per track, which give each HDA a storage capacity of 317,498,850 bytes. Sealed HDAs were standard practice on all IBM DASD hereafter. Disk units are identified as Models A2, A2F, B2, B2F, C2, and C2F with each model containing two HDAs. The models are installed in strings of units with an A2 or A2F unit required and attached to a storage control such as the IBM 3830 Model 2 or the equivalent integrated storage control of a system unit. After the A2 can be up to 3 B2 units or up to 2 B2s and a C2. The C2 unit also connects to a storage control and serves as a secondary path to itself and the A2 and B2 units. When using a C2 two I/O operations could simultaneously take place on the string, one via an A2 and a second via the C2. The valid 3350 strings are: -A, -AB, -ABB, -ABBB, -AC-, -ABC-, or -ABBC- configurations. The "x2F", as in Model A2F, unit is a normal x2 unit, but its two HDAs also have a