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How it works |
How it works
Page last updated 25/7/99 Both the Series 5, and the Geofox One have their operating systems in ROM, which the system then executes from on initial boot (or hard-reboot). This operating system then remains running, even when the machine is turned "off". The machine never actually switches off, just goes into a very low power standby mode. For this reason we had to find some way of making the machine load and execute the Linux kernel whilst EPOC was already running. This was achieved using a program called ArLo (ARM Loader), which does under EPOC what Loadlin does under DOS. When ArLo s executed, it loads the kernel image and optionally
an initial RamDisk image into memory, takes the processor out of protected
mode, and jumps to the kernel boot code. From this point Linux is in complete
control, and it overwrites the memory previously used by EPOC with itself.
Unfortunately the designed of EPOC never foresaw this situation, and they
placed some checks in the EPOC boot code which noticed whether it has booted
before since the last hard reset, and attempts to restore it's ramdisk
image if it has. There is also no way to hard reset the machine other than
bu taking all the batteries out of the machine. So, when you reboot after
running Linux, EPOC starts (because it is embedded in the firmware at the
boot vector), notices that it has been here before, then gets very confused
as it tries to use the contents of the memory even though has previously
been running and has written over most of the memory. The way to get around
this is to hold down both shift keys whilst you power the machine up after
pressing the reset switch, which forces EPOC to reinitialize the memory.
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