Atari XF551
The XF551 is generally considered the best of Atari's drive offerings; not only does it store three times as much data as the 1050, it is twice as fast and almost silent in operation.
This included the Atari 1050, a new disk drive that was built around the double-density MFM encoding standard that provided up to 180 kB of storage.
In January 1984, Commodore president Jack Tramiel got into some sort of argument with chairman of the board, Irving Gould, and left the company.
After spending some time looking for ways to re-enter the field, in July he arranged a deal to buy Atari from its owners, Warner Communications, for no cash and several million in promissory notes.
Warehouses filled with stocks of the 8-bit line were sold off at fire-sale prices pending the introduction of cost-reduced models, the XE series.
[1] By the time the stocks of these drives finally dwindled in 1986, the ST was selling strongly and the company had lost interest in the 8-bit line.
[10] As part of the XEGS launch, Atari boasted about its large library of software as well as its ability to be used as a true computer with the supplied keyboard and optional peripherals including a floppy drive.
This had led to a thriving market for 3rd party DOSes which had long supported double-density modes and the higher transfer speeds.
Atari contracted OSS to produce a new version, initially known as ADOS, which added double-sided support to its existing double-density and high-speed features.
[11] Prior to the Nintendo lawsuit, Atari claimed the only holdup on the new drive was that the documentation for the new DOS was not ready.
[11] However, DOS 2.5 lacked support for the new modes, which essentially made it a direct replacement for the 1050 rather than the major upgrade it was intended to be.
The only real complaints were the rear position of the power button,[14] which made it difficult to access in some computer desks, and that it was very "fussy" about the diskettes, rejecting as many as 20% of low-cost floppies.
[16] By the late 1980s, sales of the XE series were primarily to low-cost markets like eastern Europe and South America.
These markets were so cost-sensitive that even the low price of the XF551 was too much for most users, and the most common storage mechanism was the XC12 cassette tape system.
[12] When operating in legacy modes to read or write to disks from the 810 or 1050, the system transferred data at the original standard speed of 19,040 bps.
This speed was much lower than the SIO was capable of, and had been selected simply because that was the limit of the logic analyzer available to the engineers designing the original 810s.
[18][19] For the new drive, which operated at higher speeds and had more features, the 6507 was replaced by the Intel 8040, microcontrollers that included ROM and RAM on the same chip and thus allowed a great simplification of the controller.
[21] Most of the drives sold used a Mitsumi Electric mechanism, although a small number of later models replaced this with one from Chinon Industries.
This caused problems for a small number of programs whose copy protection relied on accurately timing the drive.
This meant the disks could be inserted in older drives also being run with DOS XE, or compatible double-density 3rd party DOSes, and at least read the files on that side.
