Palm m100 series
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The Palm m100 series consists of four Palm OS based personal digital assistants (or PDAs) titled m100, m105, m125, and m130. These models were intended to be "entry-level" PDAs, and therefore their cases were built from cheaper materials. Most notably, the covers of the LCD screens and the digitizers were plastic rather than glass, and the screens were smaller than the more expensive Palms on sale at the time.
Unlike other Palm computers, which had rechargeable batteries, they were designed to run on standard dry cell batteries (except for the m130, which uses a rechargeable battery). Data preservation occurred via a backup battery system that had a very short life and high voltage volatility, such that users had to change dry-cell batteries one at a time; users who removed all the batteries and then replaced them all could find that the backup battery had died in the time that it took to change the batteries, resulting in loss of unit memory.
There was a hinged flip screen cover with a small window over the screen through which the system clock can be viewed for a few seconds when the "scroll up" button is depressed through a hole in the cover, when the unit is not in use. There was an unnoticeable buzz that you could hear if you turned on the backlight and placed the Palm next to your ear. This was due to the power regulator sending lots of power to the screen to power the backlight. Therefore, this caused the battery to drain faster than normal.
The m100 is powered by the Motorola EZ Dragonball processor operating at 16MHz and has 2 Megabytes of RAM. It was released in August 2000. It is 4.66 inches high, 3.10 inches wide, and 0.72 inches thick. It weighs 3.7oz without batteries or screen cover. It came with a serial cable to sync with a computer and a CD ROM with Palm Desktop software. It has a durable plastic screen that will withstand falls better than glass screens, and it comes with a hinged screen cover that hangs over the screen when not in use.
The m105 is identical to the m100 but it contains 8 Megabytes of RAM, and in the box a cradle is included instead of a cable. The m105 had a problem whereby the capacitor that saved the contents of the RAM when changing batteries would fail. Several hardware hacks are available that fix this error. It was released on March 6, 2001. 
The m125 is powered by the Motorola VZ Dragonball processor operating at 33MHz. It has a 160x160 pixel greyscale LCD screen and 8 Megabytes of RAM. It was originally shipped to customers with Palm OS 4.0. The cradle connection and expansion port differs from that of the earlier models, and is identical to that of the Palm m500 series, and this model shipped with a synchronization cradle that connected to the USB port (M100 and M105 connected via the PC's serial port.) This handheld also features a memory slot which takes an SD or MMC format external memory. The Palm m125 is the last PDA manufactured by Palm that accepts user-replaceable AAA batteries.
The m130 is also powered by the Motorola VZ Dragonball processor operating at 33MHz. It has a 160x160 pixel LCD screen that supported 16 bit color. It was originally shipped to customers running Palm OS 4.1.