Conventional Memory (0 Through 640K; Upper Memory Area; Rolled-Over Memory; Ram Drive - Intermec Janus 2020 User Manual

JANUS 2020 Hand-Held Computer User's Manual

Conventional Memory (0 Through 640K)

The reader has 1MB of battery-backed dynamic RAM. The first 640K is
conventional memory and is virtually the same as that of a PC. You can use
this memory to run applications. The ROM DOS 5.0 operating system loads at
0 and works up, followed by the statements and drivers in the CONFIG.SYS
file, then COMMAND.COM, TSR (terminate and stay resident) programs, and
commands in the AUTOEXEC.BAT file.

Upper Memory Area

The area between the 640K and 1024K is known as the upper memory area.
The upper memory area is physically composed of a 256K flash ROM chip
(system flash) and the video memory chip. Like a PC, this area contains the
BIOS and video buffers. On the reader, the upper memory area also contains
PC card memory and ROM DOS. The 384K upper memory area maps just
above 640K conventional memory.

Rolled-Over Memory

The reader has 1MB of battery-backed DRAM. From the memory existing
between the 640K and 1MB boundaries, 384K is remapped or "rolled-over"
above 1MB to create the RAM drive. If you do not need the RAM drive, you
can access rolled-over memory as extended memory through a device driver or
an application that uses HIMEM.SYS.

RAM Drive

Part of rolled-over memory is configured as a RAM drive (drive E) on the
JANUS reader. The default CONFIG.SYS file loads HIMEM.SYS and uses the
SRAMDISK.SYS device driver to create the RAM drive.
You can use the RAM drive to store files just like a disk drive on your PC. File
access is usually faster on a RAM drive than a physical disk drive. Unlike a PC,
any files on the RAM drive are saved during a warm boot. However, any files
on the RAM drive are cleared when you cold boot the reader.
The reader requires 64K of the rolled-over memory area for the high memory
area (HMA) and another 64K is used as extended memory, leaving a maximum
of 256K available to store files. If you are not using a PC card, Intermec
recommends that you use the RAM drive for data files that are stored
frequently. The RAM drive is not as secure as a PC card since the drive is
erased when you cold boot the reader.
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