1.1.3.3 Types of Sector Addresses

• Physical address is address of the sector with respect to start of physical media.
• One way of addressing was to mentioning plate number , track number and sector number called as CHS address.
• CHS is simple but not used anymore. 
• ATA was using 16 bits,4 bits,8 bits for cylinder , Head and Sector respectively. Older BIOS uses 10 bits , 8 bits and 6 bits respectively.
• If ATA is connected with older BIOS, they can work with possible minimum value i.e. 10 bits, 4 bits, 6 bits so only 504 MB disks were compatible with the system. 
• To overcome this 504 MB limit , special BIOS were developed to translate addresses from application to hard drive, But it did not support hard disk larger than 8.1 GB
• BIOS were not common, if uses and investigator uses different version of BIOS then no investigation was possible.

LBA (Logical Block Addressing)

• To overcome problems in previous section, LBA was introduced.
• Due to LBA software does not require to know about hard drive geometry.
• For backward compatibility , LBS to CHS formula is there
• LBA=((CYLINDER * Heads_Per_Cylinder) + HEAD) * SECTOR - 1

• Interface Standards 

1. ATA-1:- Supporting CHS & LBA.
2. ATA-3 :- Self Monitoring Analysis and Reporting Technology. Supported Passwords
3. ATA/ATAPI-4 :- 80 Wire cable. Supported HPA
4. ATA/ATAPI-6 :- stopped supporting CHS.
5. ATA/ATAPI-7 :-

• Disk Commands

1. Controller issues commands on cable specifying disk (Master or Slave)
2. Controller specifies what exactly he wants from the specific disk. Location of the data , read , write instructions etc

• Hard Disk Passwords

1. Optional, since ATA-3
2. Can be set through BIOS or some other software.
3. Two types of passwords Master and User.
4. Master password was for company administrator in case user password is lost.
5. High security mode:- Both password could unlock the disk.
6. Maximum Security Mode :- User password to unlock, Master password to unlock only after wiping.
7. HDD will require SECURITY_UNLOCK command with password.
8. After no of unsuccessful attempts disk will freeze and rebooting was required.

• Host Protected Area (HPA)

1. Special area , generally unseen by common user. Can be configured by ATA.
2. Invented with ATA-4.
3. Computer vendor used to analysed it to detect whether disk is formatted by user or not 
4. READ_NATIVE_MAX_ADDRESS gives no all of available sectors.
5. IDENTIFY_DEVICE gives no of accessible sectors
6. the difference (if any) between commands mentioned in 4 ,5 is HPA, it was there but not seen by user
7. To remove HPA  SET_MAX_ADDRESS should be executed with proper value 
8.  Using SET_MAX_ADDRESS < READ_NATIVE_MAX_ADDRESS  will create HPA.
9. 
   

Image Source 

• Device Configuration Overlay

1. Since ATA-6
2. DCO can be used to hide the data
3. As we discussed , IDENTIFY_DEVICE command returns information about the device, DCO can be used to make IDENTIFY_DEVICE show smaller size.
4. DEVICE_CONFIGURATION_SET used to create DCO
5. DEVICE_CONFIGURATION_RESET used to remove DCO

• Serial ATA

1. Solution for traditional ATA
2. Traditional ATA cables were so big and rigid. Selecting master-slave by jumper was critical.
3. Serial ATA, Only 1 bit information is transferred at a time as compare to 16 bit information in original or parallel ATA
4. Jumpers are not required anymore
5. Controller can be placed between computer and disk so that computer will not know the type of hard drive type (SATA or PATA)