Flash Memory
From pocketnow.com
Contents |
Introduction
Flash memory is a form of nonvolatile memory (meaning that it's contents aren't lost when the storage device looses power). Adding flash memory to your Windows Mobile device will increase the number of files that you can store. Flash memory cards are also a greate way to copy files between your Windows Mobile device and your computer (given that your computer has a flast card reader). It is important to note that Flash memory can only be used for file storage on a Windows Mobile device. It cannot be used to compensate for insufficient RAM on a device.
Interpreting Sizes
In general the memory capacity of a flash memory device as printed on its label will be higher than its actual capacity. This is due to a difference in how computer systems define the term gigabytes and how the term is defined on marketing materials and packaging. In computer and other digital systems a gigabyte is defined as 2^30 (1,073,741,824). Marketting materials and packaging redefine a gigabyte as a billion bytes (1,000,000,000). Due to this difference the flash memory card's actual capacity will be about 7% less than what appears on the label.
The following shows a screenshot of how a PocketPC is reporting the size of a Compact Flash memory card that was labeled as 32 Gigabytes. This PocketPC displays sizes in megabytes. [[Image::PocketPCStorageMemory.png]]
Compact Flash
Of the flash memory formats used in Windows Mobile devices today Compact Flash has been around the longest. Compact flash cards are about the same size as a credit card cut in half vertically and vary in thickness depending on if the card is a Type 1, Type 2, or Type 3 card. According to the Compact Flash specification cards of this type could be produced in sizes up to 137 Gigabytes.
MMC and Secure Digital
MMC and Secure digital cards are visually similar to each other. They both are about the size of a stamp and are available in capacities up to 2.0 gigabytes. However secure digital cards are slightly thicker, have a write protection slot, and the specification for secure digital includes a provision for copy protection. Typically a device that accepts an SD card can also accept an MMC card. However because of the difference in thickness a device that was made for an MMC card cannot accept an SD card.
There exists a small number of SD cards with sizes of 4.0 gigabytes. However many of cards of this size are incompatible with devices that accept SD memory because many implementeds of SD hardware did not design their hardware to accept cards above 2.0 gigabytes.
SD HC
Visually identical to SD cards the SD HC memory standard raises the maximum capacity up to 32 gigabytes. Cards of this type are sometimes called SD 2.0 cards. Devices that accept SD HC memory will also work with SD cards and MMC cards. However SD HC cards will not work in devices that were designed against the SD standard.
mini SD
Mini SD cards are electrically identical to the SD cards (they are based on the same standard). So the same limitations that apply to SD cards also apply to mini SD cards such as the 2.0 gigabyte limit. However mini SD cards are about 3/4 the size of an SD card. mini SD cards can be used in SD hardware with the use of a passive mini SD to SDHC adapter.
micro SD
Micro SD cards are the smallest of the memory cards available. These diminutive memory cars are about the quarter of the size of an SD card. They have the same limitations as SD cards and adapters are available to use them in mini SD and SD slots.
micro SD HC
Micro SD HC memory cards appear identical to micro SD cards but are derived from the SD HC standard. The same restrictions that apply to SD HC also apply to micro SD HC.
