How does a processor deal with the hard disk?

[mohab]

My question is:
Lets say at a point in time the processor asks for a file called abc, does the processor manage the process of moving the hd head to the file allocation table, then getting th location of the file and ordering the head to go to the right place on the disk and reading the file....
Or does it just require file abc and the hard disk somehow manages to do th rest on it's own until it copies the abc file to memory?

 

[Mellon Head]

In most cases, the CPU passes on the request to the hard disk, and the hard disk controller takes over. It looks for the file in the master file allocation table, locates the file and loads it into its memory cache. It then signals the CPU that it has the file loaded and ready, and the CPU fetches it and does whatever it's going to do with it. The hard disk manages all of the head/sector management itself.

That's a bit simplified, but I hope it answers your question.

 

[LMiller7]

My question is:
Lets say at a point in time the processor asks for a file called abc, does the processor manage the process of moving the hd head to the file allocation table, then getting th location of the file and ordering the head to go to the right place on the disk and reading the file....

That was the case in very old computers (1980's vintage) but in more recent years these and other details are handled internally by the drive itself. A big problem with the old system is that it required the device drivers to have detailed knowledge of the drives internal organization. The new system allows the OS and device drivers to treat the hard drive as a "Black Box", a device whose function is known but with no knowledge of how it works. This allows you to replace a conventional drive with an SSD (solid state drive) and everything just works. The OS and device drivers can treat them in exactly the same way.

To the OS and device drivers the hard drive is just a place to store blocks of data. And the drive itself has no knowledge of the nature of that data. It knows nothing of file systems, files, or folders. This allows the drive to work with almost any file system, even one that did not exist when it was designed and built.

 

[mohab]

Thank you for your replies. I asked this question after installing SSDs mainly to check if spinning hard disks waste some of the processor's time dealing with their internal operations.

 

[Layback Bear]

I look at it this way.
Example:

When you use built in Windows defrag the hard drive doesn't know what is on it or where it is. The hard drive or ssd is just a storage device with little knowledge.
Window 7 knows where things are and how to get to them.
Windows 7 gives a request and instruction and the proper hardware reacts to complete the request if possible.
Hard drives and SSD's are pretty much dumb and need guidance from other sources to get anything done.

Most hardware are dumb. They don't know anything or can do anything until a request is applied. The request comes via the operating system.
Ram doesn't know why it is being request to be used. All it knows is that a request has been given and if possible it will comply.
That is why a proper operating system is required.

That is why I wonder why people complain about the price of a operating system.
All that hardware is nothing but a boat anchor without a operating system to tell it what, when and how to do things.