largely unchanged over its history. Standard RS-232c serial port (DB25 male, operating as basic 9-conductor DTE) Centronics printer port (DB25 female, officially compliant only with the most basic unidirectional standard with a single, "Busy" input line; unofficially offering some bidirectional capabilities) Atari joystick ports (DE-9 male) for the mouse and game controllers 2 MIDI ports (5-pin DIN, "IN" and "OUT") Because of its bi-directional design, the Centronics printer port can be used for joystick input, and several games used available adaptors that used the printer socket, providing two additional 9-pin joystick ports. ST-specific Monitor port (custom 13-pin DIN, 12 of the pins in a rectangular pattern, carrying signals for both RGB and monochrome monitors, monophonic audio and, in later models, composite video) ACSI (similar to SCSI) DMA port (custom-sized 19-pin D-sub, for hard disks and laser printers, capable of up to 2 MByte/s with efficient programming) Floppy port (14-pin DIN, listed as operating at 250 kbit/s) ST cartridge port (double-sided 40-contact edge connector socket, for 128 KB ROM cartridges) Monitor The ST supports a monochrome or colour monitor. The colour hardware supports two resolutions: 320 × 200 pixels, with 16 of 512 colours; and 640 × 200, with 4 of 512 colours. The monochrome monitor was less expensive and has a single resolution of 640 × 400 at 71.25 Hz. The attached monitor determines available resolutions, so each application either supports both types of monitors or only one. Most ST games require colour with productivity software favouring the monochrome. Floppy drive Atari initially used single-sided 3.5 inch floppy disk drives that could store up to 360 KB. Later drives were double-sided and stored 720 KB. Some commercial software, particularly games, shipped by default on single-sided disks, even supplying two 360 KB floppies instead of a single double-sided one, to avoid alienating early adopters. STs with double-sided drives can read disks formatted by MS-DOS, but IBM PCs can not read Atari disks, because the initial versions of TOS can recognize, read, and write to (but not create) disks in the same specification used by MS-DOS because of differences in the layout of data on track 0. Later systems 1040ST Atari upgraded the basic design in 1986 with the 1040STF, stylized as 1040STF: essentially a 520ST with double the RAM and with the power supply and a double-sided floppy drive built-in instead of external. This adds to the size of the machine,