Aitor Santamaria Merino wrote:
NT = Microkernel? Not exactly. The difference between monolithic- vs. micro- kernel is mainly how device drivers run. In a microkernel design, all device drivers run in user mode, and there's only 1 or 2 processes in kernel mode (a task switcher, and the code that actually performs individual I/O operations, since user mode programs obviously aren't allowed to perform I/O on their own ;-). The device drivers simply instruct the kernel mode task how to perform the necessary I/O for each device). In a monolithic kernel, device drivers are allowed to run in kernel mode so that they're much faster. In a microkernel design, disk I/O (for example) would take a minimum of 6 task switches (from user program to kernel, then to device driver, and then back to kernel for I/O, which then returns to the device driver, then the device driver returns to the kernel again, which finally switches back to the user program), in a monolithic kernel, it only needs to take 2 (from user program to kernel-mode device driver and back), and on the x86 (the only other chips I've done programming for were the 6502, and the original 68000) it doesn't even have to take one (if the device driver is loaded in a similar manner as a DLL). I have a link that explains the whole subject somewhere, if someone's interested I can search for it and send it on. (I may be getting details somewhat wrong though, as I haven't slept in 2 days, lol).Has anyone tried GNU-Mach and GNU-Hurd?
Minix is based on a microkernel architecture. Linux uses a monolithic kernel
instead - and this inherent difference of architecture caused that by now
well known "fall-out" between Tannenbaum and Torwalds, remember? No wonder
thus that when in March 1994 version 1.0 was presented at the University of
Helsinki, it was a totally different operating system from Minix.
I didn't have time to have a look myself, but I am willing to see a replacement of Linux kernel where one does not have to recompile, for example, to activate the FrameBuffer, to add devices or to many other things (I admit I haven't read much about the PAMs).
NT is microkernel too, in my understanding it's a little advantage over Linux at this moment (?).
Paul Case
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