On Jun 26, 21:15, Hotze wrote: bug way Acorn's RISC PC has the OS (RISC OS 3.7) in ROM, about 4MB IIRC. The original Archimedes range (1987) had RISC OS 2.0 in ROM (512K, IIRC). Usually they're mask ROMs or OTPROMs. The OS is structured as a series of about 80 relocatable modules, so if an upgrade is required, you load the relevant replacement module into RAM, and the kernel changes the links that point to it. Of course, changing the kernel module itself is a little more tricky, but it can be done -- the first RISC OS 2 upgrades had instructions on how to boot the system from a disk to load a new "utility module". -- Pete Peter Turnbull Dept. of Computer Science University of York