How Computers Work
init / systemd
PID 1, starts everything
Source board
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IO Interrupts and the BusHow Computers WorkMore terms from this board
- blocking I/Othread parked until data arrives
- bootloader (GRUB)loads the kernel
- busshared wiring (memory bus, PCIe)
- device driverkernel code speaking one device's protocol
- DMAdevice moves data to/from RAM itself, CPU freed
- event loopone thread servicing many sockets
- firmware (BIOS/UEFI)first code at power-on
- I/O-bound vs CPU-boundwaiting on devices vs on compute
- interrupta device signal that yanks the CPU to a handler
- ISR / interrupt handlerthe code that runs on an interrupt
- memory-mapped I/Odevice registers appear as memory addresses
- non-blocking / async I/Ofire many, poll readiness (epoll/io_uring)
- pollingbusy-asking if a device is ready (wasteful)
- timer interruptthe tick that preempts