The MC600 is possibly the biggest Psion computer and probably the strangest one. It is from 1989 (!) and it runs text-based DOS operating system (instead of Psion’s own ones which were GUI-based). There are MC200 and MC400 boxes with similar hardware but with the SIBO operating system.
This machine is very interesting anyway: it has pretty big screen (about 10″, monochomatic LCD with 640×200 resolution), is is light (2 kg) and it has 8086-compatible processor and 768 kB of RAM. It has the MS-DOS 3.22 build-in and it can run ordinary 16-bit DOS software. There is also 1024 kB ramdisk. The battery life is, well, impressive: 20-80 hours in dependence of used battery type (one can use a rechargeable battery or pack of 8 AA batteries). It has also standby (sleep) mode so no booting is necessary (it can be supended or resumed in less than one second).
The storage is impressive but also problematic: one can use the Psion propietary SSD cards: RAM-based ones or Flash Type I ones (of course, most of available Flash SSDs are Type II which can not be accessed by MC600). There is also optional floppy drive (I dont’ have it).
The machine is not fast by today standards, of course. It has * MHz processor (it can also run in a power-saving mode at 4.7 MHz) but it is fast enough to run software like the Gnuplot (version 3.2) the SC spreadsheet or the XVI text editor (I have not tried more). I also have ported my ddfor software to this machine (actualy I just copied it from my 200LX palmtop). It’s a very nice box for situation when one need to do relatively simple thinks but one need a comfortable keyboard, a sunlight-readable display and a very long battery life.