a couple of os questions...

[Bmxpunk86pl]

ok question 1
Why just have 15 irqs in windows, why not more to make our lives easier.

question 2
What exactly it the kernel?


i appreciate any help on this.

[JigPu]

1) Who knows? I'd bet that it probably has to do with an amount of memory allocated by the BIOS or something, so it's not exactly the easiest thing to change...

2) The kernal is what the shell covers of course! (serously!!) :D Basicly, the kernal is the real operating system that actually interfaces with the devices and BIOS and such, what sends out requests to do stuff, ect. The shell is what interfaces you to the kernal.

Just more program modular design for ya. Instead of re-writing the whole OS, they can just change the user interface (shell), or upgrade what messes with the computer itself (kernal) without having to touch the other.

JigPu

[nil_esh]

Originally posted by Bmxpunk86pl
ok question 1
Why just have 15 irqs in windows, why not more to make our lives easier.


Its been a little while since I've worked with low-level stuff, but I find this stuff really interesting.

This is just a guess:

There's IRQ0-IRQ15, correct? That's 16. Its been like this since the 286. With 4 bits you can form 16 different binary numbers (0000-1111 or 0-F in hex). IRQ comes directly to the pins on the CPU. That means 4 pins for the IRQ number and maybe one pin for IRQ-enable to signal when an interupt request is made.
Since adding pins to the CPU adds tremendous costs to producing the CPU, the cost must've outwayed the gains. Adding pins I think is the most expensive change to a processor.

A little tidbit of information: To save pins CPU designers can do little tricks like transmit the first half of data in the first half of the clock cycle, wait for the clock change from high to low (or vice versa), and then transmit the second half of data in the second half of the clock cycle. This way they unload the costs onto the motherboard manufacturers who have to now compensate for this.