Atari XF551

==> Atari XF551 --- a 5.25" floppy disk drive. Four modes of operation:
1) Single-Sided, Single-Density, 90K, 810 compatible
2) Single-Sided, Enhanced-Density, 128K, 1050 compatible
3) Single-Sided, Double-Density, 180K, Percom & other 3rd parties compatible
4) Double-Sided, Double-Density--
MFM 80 tracks x 18 sectors/track x 256 bytes/sector = 360K capacity
Writes "backwards" to the second side of the disk, when compared to a two-
sided "flippy" disk with SSDD 180K format on each side
High speed 38400 bps burst mode usable only with SpartaDOS X, SuperDOS 5.1,
TurboDOS, DOS XE, and patched SpartaDOS 3.2.
Rotaton rate: 300RPM. Since all other Atari-specific drives run at 288RPM,
this results in rare compatibility issues. Specifically, these commercial
disks do not load in, and can be damaged by, the XF551:
- Flight Simulator II (subLOGIC)
- Blue Max (Synapse)
- Bank Street Writer (Broderbund). Conflicting reports about this one.
8040 cpu + external ROM or 8050 cpu with internal ROM
Shipped with DOS 2.5 or DOS XE.
DIP switches: Both dips down: Drive 1
Left down, right up: Drive 2
Left up, Right down: Drive 3
Left and Right up: Drive 4
Chinon-built XF551-cannot read/write/format backside if no timing hole
Mitsumi-built XF551--can read/write backside if to timing hole, if formatted
Third-party upgrades for the XF551:
CSS XF Single Drive Upgrade--3.5", 720K floppy drive replacement
also read 720K 3.5" MS-DOS disks
see http://www.nleaudio.com/css/products/XFsingdrup.htm
CSS XF Dual Drive Upgrade--add 3.5" drive w/o losing the 5.25" drive
also read 720K 3.5" MS-DOS disks
see http://www.nleaudio.com/css/products/XFdualdrup.htm
CSS XF551 Enhancer--overcomes sensor for index hole, create flippy disks
see http://www.nleaudio.com/css/products/XF551enh.htm
CSS XF Update--replace drive OS, adds UltraSpeed
see http://www.nleaudio.com/css/products/XFupdate.htm
Hyper-XF-OS--avaiable for 5.25" or 3.5" floppy versions; uses sector skewing
and UltraSpeed (but no track buffer!); can use disk partitions
(2 on 5.25", 4 partitions on 3.5") with mixed Densities (S/E/D)
or standard 360kbytes (5.25") / 720kbytes (3.5"); can
theoretically read/write ST/PC 720k disks (software is missing!)
OS created by Stefan Dorndorf/Germany;
XF-Speedy--replaces the 8040 CPU with a 65C02 + ROM + Memory