Specifications

2 - 18
n Drive Quality -- High quality, DC servo direct drive motor floppy disk drives are
recommended.
n Drive Combinations -- Any combination of supported drives can be used.
n Drive Select Jumpering -- Both drives must be jumpered to the second drive select. Use a
floppy cable with a segment of wires "twisted" as is the usual practice in PC and AT
compatible systems.
n Drive Termination -- Resistive terminations should be installed only on the drive
connected to the last interface cable connector (farthest from the computer).
n 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."
n Drive Mounting -- If the computer board is to be mounted directly on a disk drive, it is
recommended that a thin metal shield be used between the disk drive and the computer
board, to reduce the possibility of electromagnetic interactions. A drive and board mounting
bracket is available as an option from Ampro.
n Dual Capacity Drives -- The Little Board/286's ROM-BIOS allows dual-capacity use of a
1.2 megabyte "high density" drive: i.e., 360 Kbyte diskettes can be read on a high density
drive. However, it is not recommended that you write to 360K diskettes on the high
density drive, as incomplete erasure may occur. (This recommendation applies to standard
AT's as well.) In addition, there are two types of floppy drives that offer dual-capacity
operation:
--Standard AT drives: the data rate shifts between 250K and 500K bits/second, but the
drive's rotational speed stays constant.
--Dual speed drives: the data rate shifts between 250K and 300K bits/second, and the
drive's rotational speed changes between 300 and 360 rpm as well.
A jumper (W19) is used to select between the two types of dual capacity drives. Refer to
Table 2-15.
Table 2-15. Dual-Speed Drive Option
W19 FUNCTION
short Dual-speed operation enabled
open Dual-speed operation disabled
Floppy Interface Configuration
The desired configuration of floppy drives (number and type) must be properly initialized in the
board's Configuration Memory. This is generally done using the Ampro SETUP utility. In
addition, the dual-speed configuration jumper option (W19) should be set according to whether
you wish dual-speed operation on dual capacity floppy drives (see Table 2-17).