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Re: comparisons



Nick Holland wrote:

This basicly means, your (typical?? whoa) 3GHz processor becomes a
8MHz 80286 whenever it has to touch the IRQ controller, or anytime the
IRQ controller touches the processor bus.  Ouch.  So, your numbers are
off by a very large factor, in parts.  If I am interpreting my
memories of how the 8259 works on the 8085 into the P4 world (HAR!),
you are only horribly crippled when programming the interrupt
controller and initially responding to the controller (and possibly
clearing the IRQ status afterwards).  Once the IRQ is sent, the
processor state save and restore would be done at full processor
speed.



Actually, in fairly recent hardware (pentium or so), I think the IRQ managment is done on the processor or on the external chipset, at real bus speed. But, on the other hand, the currently executing task will be interrupted to process the IRQ, so, cheap NIC cards can slow down overall machine performance.