How, Hard Disk capacity is increased when the number of address lines remain the same.

  • Thread starter Thread starter Ranga
  • Start date Start date
R

Ranga

Hi,

Hard Disk has only three address lines. But the capacity of the Hard
disk seem to rise from few MB to 100, 200 GB.

How will this happen?

Can anyone explain or provide any reference sites for this?

With Regards,
Ranga.
 
Ranga said:
Hi,

Hard Disk has only three address lines. But the capacity of the Hard
disk seem to rise from few MB to 100, 200 GB.

How will this happen?

Can anyone explain or provide any reference sites for this?
Click to expand...

The address lines are used to determine which of several hard disks attached
to a cable is being accessed, not to determine which location on the disk
is to be accessed. That information is passed down the data bus as a coded
command.
 
If that 3 (actually it is 5) was enough for a few MB already, why would
there be a problem for bigger drives?
Obviously the device address select DA(0-2) lines are used for something
different.

5.2.1 CS(1:0)- (Chip select)
These are the chip select signals from the host used to select the Command
Block or Control Block registers (see 7.2). .

5.2.2 DA(2:0) (Device address)
This is the 3-bit binary coded address asserted by the host to access a
register or data port in the device (see 7.2).

ATA-ATAPI specs at www.t13.org
The references I gave are from (ATA/ATAPI-6) Rev. 3
The address lines are used to determine which of several hard disks
attached to a cable is being accessed,
Click to expand...

Nonsense.
The socalled 3 'address' lines are used to select a register in both drives.
The DEV bit determines which drive will respond.

3.1.24 device selection: A device is selected when the DEV bit of the
Device register is equal to the device number assigned to the device by
means of a Device 0/Device 1 jumper or switch, or use of the CSEL signal.
not to determine which location on the disk is to be accessed.
Click to expand...

Sure it does.
That information is passed down the data bus as a coded command.
Click to expand...

Both are delivered that way.
 
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