IA64 legacy?

[CTho9305]

Does IA64 have all of the legacy stuff of IA32 like IRQs, or have we finally gotten to the point where a lot of that stuff can be dropped? I imagine x86-64 systems still have IRQs regardless of ACPI support...

 

[Locutus4657]

As far as I know ACPI is little more than a power managment protocol... That has absoultly nothing to do with IRQ's and why they're used. IRQ's are signals sent directly from the CPU from hardware to tell them that they have finished moving block x of data in to location y of memory, or any number of other things though this example is typical. I really don't know why you consider IRQ's to be legacy (i.e. bad in most peoples minds). It's a great simple way to improve interactivity with a computer, by freeing the CPU to interact with the user. I don't know why you would want to elimiate that....



<< Does IA64 have all of the legacy stuff of IA32 like IRQs, or have we finally gotten to the point where a lot of that stuff can be dropped? I imagine x86-64 systems still have IRQs regardless of ACPI support... >>

 

[Nothinman]

Yea, what Locutus said. =)

IRQs are used on every system I've used, the only real problem I see with them is the limited number on Intel boxes (but that's an x86 specific thing) and there's no queuing done, so once an IRQ is raised it can't be raised again until the CPU acknowledges and clears it. Without them the OS would have to poll each device to see if it's done doing whatever, which would not be better.

 

[CTho9305]

so does it have more? or what. I dont understand IRQs, IRQ sharing, etc, well enough i guess

 

[Nothinman]

I would assume it has more IRQs, the 15 limit was something to do with the old PICs Intel used to use. Even with IO-APIC on 32-bit machines >15 IRQs should be doable, but backwards compatibility wins out.

On my Alpha /proc/interrupts shows:

1: 6174 XT-PIC keyboard
2: 0 XT-PIC cascade
4: 740794 XT-PIC serial
8: 428462830 RTC +timer
18: 0 PYXIS halt-switch
22: 0 PYXIS timer-cascade
23: 0 PYXIS isa-cascade
24: 579688 PYXIS eth0
27: 15 PYXIS +qlogicisp
40: 3150279 PYXIS +qlogicisp
ERR: 0


So atleast 40 IRQs are possible =) But with IRQ sharing it's not really a big deal, there's only a few microseconds of delay from shared IRQs unless the drivers suck real bad.