The page pool is the amount of RAM given to running code at any given time. RAM is used for data and code - any code that cannot execute in place (XIP) in the ROM needs to be loaded into RAM and executed from there. The page pool puts a cap on how much RAM is used for code and no data is ever loaded into the pool.
For example, if you have a 2MB page pool and regularly have 4MB of code in use, most of the time will be spent loading pages into the pool and unloading other pages from the pool. On the other hand, if you regularly have 4MB of code in use with a 8MB page pool, then just 4MB of the pool will be filled and the other 4MB sitting idle. In the latter case, making the page pool larger will have no beneficial effect because all it would do would be to remove RAM that might otherwise have been used for data.
Most of the Windows Mobile devices are preconfigured with a page pool between 4 to 8MB. The A17 Dell Axim x51v WM5 ROM has a default page-pool of 8MB. Here are some default page-pools:
| Device | Page Pool Size |
|---|---|
| hx4700 | 4.8MB |
| Ipaq 2110 | 5M |
| Dell x51v | 8M |
Depending on your device, the ROM image to modify (assumed to be the vanilla official ROM in this tutorial), you would load the image file (ending in nb0) in a hex editor and find the following word sequence:
| Device | Word Sequence |
|---|---|
| hx4700 | FF FF FF FF FF FF FF FF 9B 4F FF FF 64 B0 00 00 64 00 00 00 74 9A 1F 80 00 00 48 00 |
| Dell x51v | FF FF FF FF FF FF FF FF 9B 4F FF FF 64 B0 00 00 ?? ?? ?? ?? ?? ?? ?? ?? 00 00 80 00 |
where the last 4 words is the value in MB of the page-pool size. Given the example above:
| Device | Page Pool Words | Page Pool Size |
|---|---|---|
| hx4700 | 00 00 48 00 | 4.8MB |
| Dell x51v | 00 00 80 00 | 8MB |
These last 4 words can then be changed in order to change the page pool. Here is a shortcut table for the page-pool size:
| Words | Page Pool Size |
|---|---|
00 00 80 00 | 8MB |
00 00 C0 00 | 12MB |
00 00 00 01 | 16MB |
00 00 80 01 | 24MB |
00 00 00 02 | 32MB |
In order to flash the image, the crc file may need to be modified with the new CRC of the image file after the changes - this can vary from system to system.
Unit Zero's page pool editor for the Dell Axim x51v can be downloaded from here:
and it supports multiple ROMs from various cooks.