It also implemented a "burst mode" that improved transfer speeds, helping address the very slow performance of previous Commodore drives.
Earlier Commodore drives used a custom group coded recording format that stored 170 kB per side of a disk.
This made it fairly competitive in terms of storage, but limited it to only reading and writing disks from other Commodore machines.
Adding double-density MFM encoding allowed the drive to read and write contemporary CP/M disks (and many others).
The 1571 was designed to accommodate the C128's "burst" mode for faster disk access, however the drive cannot use it if connected to older Commodore machines.
There is also an undocumented command which allows the user to independently control either of the read/write heads of the 1571, making it possible to format both sides of a diskette separate from each other, however the resultant disk cannot be read in a 1541 as it would be spinning in reverse direction when flipped upside down.
The 1571 is not 100% low-level compatible with the 1541; however, this isn't a problem except in some software that uses advanced copy protections such as the RapidLok system found on MicroProse and Accolade games.
A version 2 ROM was released, but though it cured the initial bug, it introduced some minor quirks of its own – particularly with the 1541 emulation.
As with the 1541, Commodore initially could not meet demand for the 1571, and that lack of availability and the drive's relatively high price (about US$300) presented an opportunity for cloners.
Two 1571 clones appeared, one from Oceanic and one from Blue Chip, but legal action from Commodore quickly drove them from the market.
The worst case pattern 1001 may cause a saddle condition where a false data bit may occur.
Numerous commercial and public-domain programs for this purpose became available, the best-known being SOGWAP's "Big Blue Reader".