HAL

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I am trying to get my head around the definition of HAL and what it exactly is. I have read the use of HAL across ACPI and Multiprocessors but what does HAL exactly mean when they say the the computers should have similar or the same HAL?

 

answer?

 

Am still a little confused.

1. Does it mean HAL is a layer that allows the kernel to run of different hardware without the need to recompile the kernel?

2. When preparing SysPrep and RIPrep, why is it necessary to have computers with the same or similar HAL if the definition of HAL is to allow the kernel to run on any architecture without the need to recompile it?

 

Bear in mind I may be wrong, but
1) Yes
2) HAL is configured during installation. Any image of the system will have the same HAL.

 

What do you mean by "HAL is configured during installation. Any image of the system will have the same HAL" specifically "Any image of the system will have the same HAL"? If every system has the same HAL, why is there a need to make sure that it have the same or similar HAL?

 

In addition to my query, I would also like to know you can tell if a PC has the same or similar HAL without installing Windows on it or when the computer is brand new with no operating system of any sort. Also what if the hardware is different e.g. different motherboard same chipset or same motherboard different chipset, etc?

 

Every image of the system will have the same HAL. If the new hardware requires a different configuration you're screwed, because the HAL is set during installation and merely copying an image is not installation.

 

HAL is an general System design concept, it stands for Hardware Abstraction Layer.

Below is the windows definition of a 'HAL'.

In reality most of the 'HAL' in windows is performed by device drivers so it is not called the HAL.

The thing that is called the HAL is a DLL driver for the motherboard and processor.

There are two different HAL DLL's for x86 systems, one called Halacpi.dll and one called Halmacpi.dll. The second one has SMP support. The other difference is ACPI vs APIC.

There is only one HAL on 64 bit systems.

The HAL gets chosen and installed by the windows installer on installation on 32 bit machines.

This book will tell you most of what you need to know for Windows OS design :-

http://technet.microsoft.com/en-us/sysinternals/bb963901.aspx

 

Thanks. Ok just to clarify what you mentioned.

1. HAL is a layer governed by drivers depending on whether the PC has a single processor or multiple processors. Is this correct? Does that mean if every PC that has a single processor has the same HAL despite different chipsets, BIOS, etc?

2. These drivers allow Windows XP for example to communicate with the hardware rather than directly communicating with the hardware itself. Is this correct?

3. Based on the correctness of the answers above, how do you tell if a PC has the same or similar HAL apart from the fact that a single or multiple processor(s) are installed?

 

HAL as a term is not owned by windows, it has a wider definition. Thats what the first definition refers to.

The rest refers to what windows calls a 'HAL'.

Read what I said :-

All 64 bit windows systems have one HAL.

Two HAL's exist for 32 bit systems, one for ACPI and one for APIC motherboards.

Device Drivers abstract the OS and other programs from devices. Devices are hardware correct.

Look at the folder and see what DLL is installed ? Look at the registry and see if the DLL is referenced ? Look at various DLL resource strings that appear on the windows UI interface dialogs.

Eg.
http://support.microsoft.com/kb/298898

 

No. There are other criteria that have to be met for the hardware to be considered homogeneous.

Yes. That way the kernel can stay the same because the HAL presents a consistent interface to the kernel, regardless of the hardware.

I'd have to google that one.

 

Thanks. I was aware that I can view the HAL by looking under Device Manager however my question is how do you know a PC has the same HAL without installing an OS.

Also I didn't follow what you meant "Device Drivers abstract the OS and other programs from devices. Devices are hardware correct." What does that mean in steps please?