How to disable entry into IDLE mode:

Many of today's newer ATA interface drives have automatic energy savings
modes implemented by default. The drive's typically are designed to go into
an Idle mode which reduces power consumption and parks the drive heads
after a defined period of inactivity.  If the inactivity period continues
to another defined interval, the disc drive will further reduce its power
consumption by spinning down the platters and entering Standby mode.

When the drives are Idle or in Standby, any subsequent disc I/O will "wake
them up" and enter Active Mode. This requires a modest amount of time that
may not be desired.  Disc drive Power Management Commands control these
features and can be used to enable, disable or change the activation
intervals of the power saving modes.  A general command FBh is used to
cause a drive to enter Active mode and set the Idle timer.  If the Idle
timer is set to 0 then the power management mode is disabled until a cold
boot.

The no_idle.exe utility can be run through the config.sys file or the
autoexec.bat file.  There is no memory overhead from the program which
simply runs and then quits.

The command line switches d0 and d1 tell which
drives are have the power management defaults turned off.  Usage:

No IDLE v1.1
executable:    no_idle.exe d0 d1 = disable drive 0 and drive 1
               no_idle d0        = disable drive 0 only!

device driver: device=no_idle.exe d0 d1 = disable both
               device=no_idle.exe d1 = disable drive 1 only!

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An alternative approach that uses a simple 43 byte .COM file is given
below:

It can be created through the DOS Debug utility.  Two Debug script
files are included, one for each drive:
                master =  no_idle0.scr
                slave  =  no_idle1.scr

At the DOS prompt simply type:
                             debug <no_idle0.scr

This will cause the script file to be redirected into Debug with the
following results (without the comments and the xxxx is system dependant):

-n no_idle0.com              program name
-a 100                       assemble at memory location 100
xxxx:0100 call 120           call the instruction at location 120
xxxx:0103 mov dx,1f6         select the drive/head register
xxxx:0106 mov al,a0          setup for drive 0 (b0 for drive 1)
xxxx:0108 out dx,al          output to the port address
xxxx:0109 call 120           wait while busy
xxxx:010C mov dx,1f2         select the sector count/timer register
xxxx:010F mov al,0           set it to 0 msecs
xxxx:0111 out dx,al          output to the port address
xxxx:0112 call 120           wait while busy
xxxx:0115 mov dx,1f7         select the drive command register
xxxx:0118 mov al,fb          setup the Active/Set Idle command
xxxx:011A out dx,al          output to the port address
xxxx:011B call 120           wait while busy
xxxx:011E nop                no operation (slight pause)
xxxx:011F nop
xxxx:0120 mov dx,1f7         select the status register
xxxx:0123 in al,dx           input from the port
xxxx:0124 and al,80          isolate the busy bit
xxxx:0126 jnz 120            jump if not zero to location 120
xxxx:0128 nop
xxxx:0129 ret                return (finished)
xxxx:012A
-rcx
CX 0000
:2a                          number of bytes to save
-w
Writing 0002A bytes
-q                           as in quit

When finished, a very small no_idle0.com file will exist that can be run to
disable the Idle mode.  The statement @no_idle0.com may be added to your
autoexec.bat file.