ATA Features
| The ATA standards have gone a long way toward eliminating incompatibilities and problems with interfacing IDE drives to ISA/PCI bus systems. The ATA specifications define the signals on the 40-pin connector, the functions and timings of these signals, cable specifications, and so on. The following section lists some of the elements and functions defined by the ATA specifications. ATA CommandsOne of the best features of the ATA interface is the enhanced command set. The ATA interface was modeled after the WD1003 controller IBM used in the original AT system. All ATA drives must support the original WD command set (eight commands) with no exceptions, which is why ATA drives are so easy to install in systems today. All IBM-compatible systems have built-in ROM BIOS support for the WD1003, so they essentially support ATA as well. In addition to supporting all the WD1003 commands, the ATA specification added numerous other commands to enhance performance and capabilities. These commands are an optional part of the ATA interface, but several of them are used in most drives available today and are very important to the performance and use of ATA drives in general. Perhaps the most important is the IDENTIFY DRIVE command. This command causes the drive to transmit a 512-byte block of data that provides all details about the drive. Through this command, any program (including the system BIOS) can find out exactly which type of drive is connected, including the drive manufacturer, model number, operating parameters, and even the serial number of the drive. Many modern BIOSs use this information to automatically receive and enter the drive's parameters into CMOS memory, eliminating the need for the user to enter these parameters manually during system configuration. This arrangement helps prevent mistakes that can later lead to data loss when the user no longer remembers what parameters he used during setup. The Identify Drive data can tell you many things about your drive, including the following:
Several public-domain programs can execute this command to the drive and report the information onscreen, including IDEDIAG, which is available from http://www.penguin.cz/~mhi/idediag, and HWINFO, which is available from http://www.hwinfo.com. I find these programs especially useful when I am trying to install ATA drives on a system that has a user-defined drive type but doesn't support autodetection and I need to know the correct parameters for a user-definable BIOS type. These programs get the information directly from the drive. Two other important commands are the Read Multiple and Write Multiple commands. These commands permit multiple-sector data transfers and, when combined with block-mode PIO capabilities in the system, can result in incredible data-transfer rates many times faster than single-sector PIO transfers. Some older systems require you to select the correct number of sectors supported by the drive, but most recent systems automatically determine this information for you. Many other enhanced commands are available, including room for a given drive manufacturer to implement what are called vendor-unique commands. Certain vendors often use these commands for features unique to that vendor. Often, vendor-unique commands control features such as low-level formatting and defect management. This is why low-level format programs can be so specific to a particular manufacturer's ATA drives and why many manufacturers make their own LLF programs available. ATA Security ModeSupport for hard disk passwords (called ATA Security Mode) was added to the ATA-3 specification during 1995. The proposal adopted in the ATA specification was originally from IBM, which had developed this capability and which had already begun incorporating it into ThinkPad systems and IBM 2.5" drives. Because it was then incorporated into the official ATA-3 standard (finally published in 1997), most other drive and system manufacturers have also adopted this, especially for laptop systems and 2.5" drives. Note that these passwords are very secure. Also, if you lose or forget them, they usually cannot be recovered and you will never be able to access the drive. More on that later.... Hard disk security passwords are set via the BIOS Setup, and not all systems support this feature. Most laptops support hard disk security, but most desktops do not. If supported, two types of hard disk passwords can be set, called user and master. The user password locks and unlocks the disk, whereas the master password is used to only unlock. You can set only a user password, or you can set user+master, but you cannot set a master password alone. When a user password is set (with no master), or when both user+master passwords are set, access to the drive is prevented (even if the drive is moved to a different system) unless the user (or master) password is entered upon system startup. The master password is designed to be an alternative or backup password for system administrators as a master unlock. With both master and user passwords set, the user is told the user password but not the master password. Subsequently, the user can change the user password as desired; however, a system administrator can still gain access by using the master password. If a user or user+master password is set, the disk must be unlocked at boot time via a BIOS-generated password prompt. The appearance of the prompt varies from system to system, but in IBM systems the prompt is graphical. An icon consisting of a cylinder with a number above it (indicating the drive number) next to a padlock appears onscreen. If the hard disk password prompt appears, you must enter it; otherwise, you will be denied access to the drive and the system will not boot. As I said earlier, if you forget the user password (with no master) or both the user and master passwords (if both are set), you will not be able to gain access to the drive, even if you move it to another system and even if the other system does not support ATA Security Mode. The drive will have essentially become a paper weight. As with many security features, a workaround might be possible if you forget your password. In this case, at least one company can either restore the drive to operation (with all the data lost) or restore the drive and the data. That company is Nortek (see http://www.nortek.on.ca for more information). The password removal procedure costs $85$295, and you must provide proof of ownership when you send in the drive. As you can see, the cost is generally more than the cost of a new drive, so it is worthwhile only if you absolutely need the data back. Hard disk passwords are not preset on a brand-new drive, but they might be preset if you are buying a used drive or if the people or company you purchased the drive or system from entered them. This is a common ploy when selling drives or systems on eBayfor example, the seller might set supervisor or hard disk passwords and hold them until payment is received. Or he might be selling used product "asis" for which he doesn't have the passwords, which renders them useless to the purchaser. Because of this, I never recommend purchasing a laptop or hard drive used unless you are certain that no supervisor or hard disk passwords are set. Most systems also support other power-on or supervisor passwords in the BIOS Setup. In most systems, when you set a supervisor password, it automatically sets the hard disk password to the same value as well. In most cases, if a supervisor password is set and it matches the hard disk user or master password, when you enter the supervisor password, the BIOS automatically enters the hard disk password at the same time. This means that even though a hard disk password is set, you might not even know it because the hard disk password is entered automatically at the same time as you enter the supervisor password; therefore, you won't see a separate prompt for the hard disk password. However, if the drive is later separated from the system, it will not work on another system until the correct hard disk password is entered. Without the services of a company such as Nortek, you can remove a hard disk password only if you know the password to begin with. Host Protected AreaMost PCs sold on the market today include some form of automated product recovery or restoration feature that allows a user to easily restore the operating system and other software on the system to the state it was in when the system was new. Originally, this was accomplished via one or more product recovery CDs containing automated scripts that reinstalled all the software that came preinstalled on the system when it was new. Unfortunately, the CDs could be lost or damaged, they were often problematic to use, and including them by default cost manufacturers a lot of money. This prompted PC manufacturers to move the recovery software to a hidden partition of the boot hard drive. Although this wastes some space on the drive, the recovery software normally fits on from one to four CDs, which occupies 1GB3GB of drive space. With 60GB or larger drives, this amounts to 5% or less of the total space. Still, even the hidden partition was less than satisfactory because the partition could easily be damaged or overwritten by partitioning software or other utilities, so there was no way to make it secure. In 1996, Gateway proposed a change to the ATA-4 standard under development that would allow a space called the host protected area to be reserved on a drive. This change was ratified, and the HPA feature set was incorporated into the ATA-4 specification that was finally published in 1998. A separate BIOS firmware interface specification called Protected Area Run Time Interface Extension Services (PARTIES) was initiated in 1999 that defined services an operating system could use to access the HPA. The PARTIES standard was completed and published in 2001 as NCITS 346-2001, Protected Area Run Time Interface Extension Services. The HPA works by using the optional ATA SET MAX ADDRESS command to make the drive appear to the system as a slightly smaller drive. Anything from the new max address (the newly reported end of the drive) to the true end of the drive is considered the HPA and is accessible only using PARTIES commands. This is more secure than a hidden partition because any data past the end of the drive simply cannot be seen by any normal application, or even a partitioning utility such as PartitionMagic or Partition Commander. Still, if you want to remove the HPA, you can use some options in the BIOS Setup or separate commands to reset the max address, thus exposing the HPA. At that point, you can run something such as PartitionMagic or Partition Commander to resize the adjacent partition to include the extra space that was formerly hidden and unavailable. Most new systems using Phoenix FirstBIOS come with their recovery software and diagnostics in the HPA because this is part of the new Phoenix FirstBIOS core managed environment (cME), which is used by a large number of OEMs (including IBM) on most desktop and laptop systems starting in 2003.
ATA Packet InterfaceATA Packet Interface (ATAPI) is a standard designed to provide the commands necessary for devices such as CD-ROMs, removable media drives such as SuperDisk and Zip, and tape drives that plug in to an ordinary ATA (IDE) connector. The principal advantage of ATAPI hardware is that it's cheap and works on your current adapter. For CD-ROMs, it has a somewhat lower CPU usage compared to proprietary adapters, but there's no performance gain otherwise. For tape drives, ATAPI has the potential for superior performance and reliability compared to the popular floppy controller attached tape devices. Although ATAPI CD-ROMs use the hard disk interface, this does not mean they look like ordinary hard disks. To the contrary, from a software point of view, they are a completely different kind of animal. They most closely resemble a SCSI device. All modern ATA CD-ROMs support the ATAPI protocols, and generally the terms are synonymous. In other words, an ATAPI CD-ROM is an ATA CD-ROM, and vice versa. Caution Most systems starting in 1998 began supporting the Phoenix El Torito specification, which enables booting from ATAPI CD or DVD drives. Systems without El Torito support in the BIOS can't boot from an ATAPI CD or DVD drive. Even with ATAPI support in the BIOS, you still must load a driver to use ATAPI under DOS or Windows. Windows 95 and later (including 98 and Me) and Windows NT (including Windows 2000 and XP) have native ATAPI support. Some versions of the Windows 98 and Me CD-ROMs are bootable, whereas all NT, 2000, and XP CD-ROMs are directly bootable on those systems, greatly easing installation. I normally recommend keeping ATA devices you will be accessing simultaneously on separate channels. Because ATA does not typically support overlapping access, when one drive is being accessed on a given channel, the other drive on the same channel can't be accessed. By keeping the CD-ROM and hard disk on separate channels, you can more effectively overlap accessing between them. One other caveat is that a parallel ATA device such as a hard drive might be incapable of functioning if another parallel ATAPI device (CD or DVD drive) is master. Therefore, in most cases you should try to set parallel ATA hard drives as master (device 0) and parallel ATAPI drives as slave (device 1) on a given cable. |
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