One of the most talked about aspects of the Windows Mobile 5  OS is its redesigned memory paradigm called "Persistent Memory Storage."  We've received many questions about this new memory management scheme, and here we'll attempt to explain it.

First, two definitions:

RAM, or Random Access Memory, is a type of memory chip referred to as volatile. Volatile memory requires a constant flow of electricity to retain the data stored within it. RAM is the type of memory installed inside your Windows PC and is used to run programs and to store active files.  When you turn off your PC, power to RAM is cut; when you turn your computer back on, it reboots, or moves data back to the cleared RAM from the hard drive.

ROM, or Read Only Memory, is nonvolatile memory.  Nonvolatile memory does not require a constant power source to retain data.  This type of memory is found in flash memory cards like CompactFlash or Secure Digital cards.  Data stored in ROM memory is only lost when it is purposely removed.

In all versions of the Pocket PC and/or Windows Mobile operating systems before Windows Mobile 5, Pocket PC memory was managed in the way illustrated below.  RAM and ROM chips worked together to store data and run applications. The operating system was stored in the ROM and could not be changed; in this way, the unchanged OS could be restored in the event of an error.  The RAM memory chip pulled double duty.  In addition to storing active programs and files, just like the RAM in your PC, it also stored all data, applications and settings that you entered from the time you first turned on your Pocket PC, like your PC's hard drive.

 

Persistent Memory Storage, the Windows Mobile 5 memory scheme, manages memory more like your desktop or laptop PC.  The ROM chip stores all data (like your PC's hard drive), and the RAM is dedicated to active memory (like your PC's RAM).

 

Persistent Memory Storage has several advantages over the previous memory scheme. First, because all information is stored in the ROM, losing power does not clear your Pocket PC's memory.  Second, since all data is saved in the nonvolatile ROM chip, the RAM chip has no need for constant power from the battery, so the battery is not always being drained.  Third, because the full capacity of the RAM is free for active system memory, programs should run faster and more applications will be able to run at the same time.

Persistent Memory Storage is also built into Windows Mobile 6.

 

Was this article helpful? Let us know.

Still have questions? E-mail us.