IRQ & IRQL

NTDEV
1

Hi everyone,
I have some confused questions here.

  1. IRQ is dependent on hardware, while IRQL is independent on hardware, why?
  2. What advantage does taking IRQL in Win2K/XP have?
  3. Essentially,what is the difference of IRQ and IRQL ?

Thanks a million.

Regards,
Andy

2

IRQ is hardware and is documented in various Intel manuals for the CPU,
8259A, & APIC.

IRQL is an abstract hardware/software priority scheme. Read some books such
as Oney’s WDM Version 2 book.

----- Original Message -----
From: “Andy Hao”
Newsgroups: ntdev
To: “NT Developers Interest List”
Sent: Tuesday, April 01, 2003 7:27 PM
Subject: [ntdev] IRQ & IRQL

> Hi everyone,
> I have some confused questions here.
>
> 1. IRQ is dependent on hardware, while IRQL is independent on hardware,
why?
> 2. What advantage does taking IRQL in Win2K/XP have?
> 3. Essentially,what is the difference of IRQ and IRQL ?
>
> Thanks a million.
>
> Regards,
> Andy
>
>
>
> —
> You are currently subscribed to ntdev as: xxxxx@yoshimuni.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com
>

3

> 1. IRQ is dependent on hardware, while IRQL is independent on
hardware, why?

IRQL values 0, 1, and 2 - PASSIVE, APC and DISPATCH - are
software-only construct.
Higher IRQL values are mapped to IRQs.

Max