Specifications

Hardware Configuration
2–17
Note
For maximum reliability, keep the cable between the board and
the device it drives to 10 feet or less in length.
The parallel port incorporates chip protection circuitry on some inputs, designed to minimize the
possibility of CMOS “latch up” due to printer or other peripheral being powered up while the Little
Board/486i is turned off.
2.8 FLOPPY DISK INTERFACE
The on-board floppy disk controller and ROM BIOS support one or two floppy disk drives in any of
the standard DOS formats shown in Table 2-12.
Capacity Drive Size Tracks Data Rate
360K 5-1/4 inch 40 250 KHz
1.2M 5-1/4 inch 80 500 KHz
720K 3-1/2 inch 80 250 KHz
1.44M 3-1/2 inch 80 500 KHz
Table 2-12 Supported Floppy Formats
2.8.1 Floppy Drive Considerations
Nearly any type of soft-sectored, single or double-sided, 40 or 80 track, 5-1/4 inch or 3-1/2 inch
floppy disk drive is usable with this interface. Using higher quality drives improves system reliability.
Here are some considerations about the selection, configuration, and connection of floppy drives to
the Little Board/486i.
! Drive Interface—The drives must be compatible with the board’s floppy disk connector signal
interface, as described below. Ampro recommends any standard PC-or AT-compatible 5-1/4 inch
or 3-1/2 inch floppy drive.
! Drive Quality—Use high quality, DC servo, direct drive motor floppy disk drives.
! Drive Select Jumpering—Both drives must be jumpered to the second drive select.
! Floppy Cable—For systems with two drives, use a floppy cable with conductors 10-16 twisted
between the two drives. This is standard practice for PC-compatible systems. If you want to use a
standard dual-drive cable with a combination floppy drive (with both 3.5 inch and 5.25 inch
drives on the same connector), connect the drive to the non-twisted connector to configure the 3.5
inch drive to be A:.
! Drive Termination—Resistive terminations should be installed only on the drive connected to
the last interface cable connector (farthest from the board). Near-end cable termination is
provided on the Little Board/486i.
! Head Load Jumpering—When using drives with a Head Load option, jumper the drive for head
load with motor on rather than head load with drive select. This is the default for PC-compatible
drives.