- Operating system
- Tech specs
- Form factors
- Touchscreen vs Keypad
Processing power varies across the range of PDAs according to price and functionality. As with most computing devices, newer models make improvements with processing power and speed.
PDAs with an Intel XScale PXA27x processor tend to be found in devices at the high end of the market geared toward speed and maximum processing power. Speeds range between 104MHz and 624MHZ. The PXA270 processor included enhancements for audio and video performance and 3D graphics as well as other CPU improvements.
The Intel PXA26x processor group is based on 32-bit processor in 200MHz, 300MHz and 400MHz versions which allow more capabilities into the device by stocking chips and reducing the number of components. The PXA255 runs at 200MHz, 300MHz and 400MHz and offers reduced power consumption compared to older processors.
PDAs running a Samsung S3C2410 or S3C2440 processor, which are based on an ARM920T core, can run at 230MHz and 266MHz. This processor is more often used in cheaper devices because of the system-on-a-chip design that integrates some features within the chip itself. The chip is available with flash memory, SD RAM and support for SD and MMC card slots. It can be used with Windows, Palm and Symbian devices.
The Texas Instruments OMAP processors are used in some PDAs and are most often found in devices that include phone functionality. There are a number of versions, including OMAP3xx, 1510, 161x, 1710 and 2420, with the 310 and 1570 common in business-oriented devices.
Most PDAs feature two types of memory - RAM and ROM. RAM is used by the processor to hold data that is accessed while the computer is running, and the data is loaded and reloaded as the device is turned on and off. The more RAM, the faster the processor can work because it accesses more information from memory rather than the hard drive. ROM, or Read Only Memory, is also sometimes referred to as non-volatile memory because it is not lost or reloaded when the device is turned on or off.
In devices where memory is used by applications, it can reduce the amount of storage space available for user data. The range for RAM is between 16MB and 256MB, although BlackBerry devices tend to be somewhat lower. Some advertisements will state the separate figures for RAM and ROM, which gives a better idea of actual user storage capacity. Others may just list the RAM or Memory figure, which also includes the storage capacity for user data.
Some devices are appearing on the market that have hard drive storage. The Life Drive, for example, has a 4GB hard drive and 3.85GB is available for user storage. Most PDAs also include a slot for a removable memory card that is used for storing data between transfers and updates with the PC, or for some applications or files. They range in capacity from 128MB to 2GB depending on the format. Most PDAs will have a multi-format slot that can take one or more cards in formats such as SD, miniSD, MMC, CF (I and II) and SDIO. For more on removable memory cards, see the buying guide on storage cards.