Memory and the Modern Palm
Continued from Previous Page
ON THE PALM
Memory usage on the Palm falls into four broad
descriptive categories: operating system storage,
program and file storage, program working space, and
removable media. OPERATING SYSTEM STORAGE
An operating system acts as a digital middleman between
programs and the device hardware, providing common
services like file handling and a standard graphical user
interface. In the original Pilot and PalmPilot
organizers, the Palm Operating System (Palm OS) was
stored in a 1 Megabyte ROM chip. Later, when the Palm
III debuted, it came with OS version 3.0 filling 1.2
Megabytes of a 2 Megabyte flash ROM. The seemingly small
addition of flash has allowed Palm III models to keep up
with the times. In the last few years, Palm OS has been
steadily upgraded to versions 3.1, 3.3, and 3.5, adding
support for better communications, networking and display
modes. The flash ROMs also contained 800k of unused flash
memory--space that could be turned into usable storage
for programs and data by enterprising companies
like TRG (now HandEra), who made programs to move
files from RAM into the spare flash. Unfortunately,
when Palm OS grew to version 3.5, its larger size left
only 300k of extra storage space. The good news is that
Palm's new m500 and m505 organizers now ship with OS 4.0
occupying only 2.3 Megabytes of new larger 4 Megabyte
flash ROMs, leaving a nearly two Megabytes "free"
additional storage in those units.
PROGRAM AND FILE STORAGE
A common misconception about Palm memory is that an
8-Megabyte Palm is roughly equivalent to a PC with 8
Megabytes of RAM, which, while firmly in the "puny"
category today, was fairly common only a few years ago.
The difference, however, is that a Palm organizer does
not have a hard drive on which to store files that are
not currently in use. To make up for this, the majority
of RAM on a Palm is actually reserved for use as a
"virtual hard drive" to store files and data. Only a very
small amount of RAM is actually left for currently active
program to be used as ordinary RAM.
The file storage area of memory is called the "storage
heap". The storage heap is electronically safeguarded
from unintended modification by misbehaving apps, giving
robustness required of a hard-drive replacement. Unlike
a hard drive, however, data in the Palm OS storage heap
can still be directly accessed (read) by applications and
the Palm's microprocessor. This is why Palm apps rarely
have manual "load" and "save" commands; files can often
be used while they're still on the storage heap. This
also eliminates the wasteful delays, extra memory
overhead, and risk of loss data encountered under less
evolved operating systems like Pocket PC. In that OS,
data stored in file memory must first be copied to
precious working memory before it can be used, and later
copied back to permanently save any changes.
PROGRAM WORKING SPACE
The small amount of working RAM allocated to running
programs is known as the "dynamic heap". The size of the
dynamic heap varies with OS version and total available
RAM. In Palm OS 2.0 and earlier, it was fixed at 64k.
This amount was increased in OS 3.0 to 96k, but was
changed in OS 3.5 to be variable, ranging from 64k to
256k, depending the total amount of RAM on the device.
>> Continued on Next Page...
News Home
| Page 01
| Page 02
| Page 03
| Page 04
| Page 05
|
