A. Well you've come to the right place for your answer. Let's start with the definition; ATAPI is an acronym that means "AT Attachment Packet Interface". ATAPI does not really define an interface per se, but instead it outlines the specifications for devices that use an IDE (or Integrated Drive Electronics) port--the same port used by your IDE hard drives.
To understand how ATAPI devices fit into the scheme of today's PCs,
you need to know a little history. IDE ports appeared around 1988
as a simple and inexpensive means of connecting high-capacity hard
drives to a computer. In fact, IDE ports proved so simple and standard
that they were soon supported through motherboard BIOS (a trend that
continues today). There was just one little problem with IDE ports--they
only supported hard drives. When early CD-ROM drives and tape drives
entered the market, each drive required its own proprietary drive controller.
You still
see this today by looking at the proprietary CD-ROM interfaces
on older Creative Labs Sound Blasters.
Well, PC designers are always looking to do more with less. They soon realized that most PCs offer two IDE ports (a primary and secondary port), and an IDE port can handle two drives, but most PCs only have one or two drives. So rather than let those two or three extra ports go to waste, designers developed a specification which would allow non-hard drive devices to use the IDE port too. This became the ATAPI specification.
The one limitation to ATAPI is that such devices are not supported in
BIOS. For example, you need a device driver for your CD-ROM, and the corresponding
drive entry in your CMOS Setup should be set for "none" or "not installed".
Today, the most popular ATAPI IDE device is the CD-ROM. ATAPI tape
drives are starting to become popular, and ATAPI Zip drives (from Iomega)
are appearing. As you get deeper into the world of computing, you'll find
that ATAPI devices will play important roles in PC building and upgrading.
Ultra DMA/33
Q. I've been looking at some new Pentium motherboards lately to upgrade
my aging system, and I'm seeing references to something called Ultra
DMA/33. What is Ultra DMA/33, and why is it important?
A. That's such a timely question! Ultra DMA/33 is part of the Ultra
ATA specification developed by Intel and Quantum now being employed in
the latest PCs which allows for an improved hard drive interface--the
actual 40-pin EIDE connector itself is unchanged,
but the protocol used to handle data transfer between the drive and
controller board has been enhanced. Ultra DMA/33 doubles the current
burst data transfer rate from 16.6MB/sec (with PIO Mode 4 data transfers)
to 33MB/sec.
If you've ever waited around for large applications to load, or seen Windows stammer and hesitate during disk access, you already know the limitations of current drive interfaces. By doubling the potential data transfer rate of a hard drive with Ultra DMA/33, you'll see that the system boots faster, loads applications faster, and hesitates less (if at all) during disk access--especially during data-intensive reads such as audio and video data.
To take advantage of Ultra DMA/33 on your system, you'll need a hard drive and controller which are both designed to support Ultra DMA/33. There are three ways to accomplish this:
* Buy a new PC that has the Intel 430TX or compatible chipset (which supports
Ultra DMA/33) and an Ultra ATA hard drive.
* Buy a new motherboard with the Intel 430TX chipset and an Ultra ATA hard
drive.
* Buy an Ultra ATA hard drive and an Ultra ATA-compatible drive controller
card
(you'll need to disable any other drive controller in the PC).
Keep in mind that the Ultra ATA specification is fully backward-compatible with current EIDE (or "Fast ATA") devices. This means you can continue to use your EIDE hard drives with an Ultra ATA motherboard or drive controller, or use a new Ultra ATA hard drive with your existing EIDE motherboard or controller. The only problem is that your drive system will be limited to the PIO Mode 4 data transfer rate of 16.6MB/sec. You'll also be limited to slower data transfer rates if you mix EIDE (Fast ATA) and Ultra ATA drives on the same drive controller port.
If you want to take a closer look at Ultra ATA and Ultra DMA/33,
check out the VIA web site at http//www.via.com.tw/dma33.htm).
To see an Ultra DMA/33 motherboard, glance at the Freetech Condor motherboard
at (http://www.freetech.com/products/F78spec.htm)
EIDE and SCSI hard drives
Q. I built a computer using a Tyan Titan III motherboard. The motherboard
has an on-board EIDE controller that supports 4 hard drives (through a
primary and secondary channel). I currently have two hard drives and a
6X internal
CD-ROM connected to the primary and secondary ports. If I choose to
switch to SCSI hard drives and install a SCSI controller, will I
still be able to keep my IDE CD-ROM connected to the on-board IDE
controller? Can I mix EIDE and SCSI hard drives?
A. Yes, you should be able to leave your CD-ROM drive by itself on the secondary channel. Just remember to enter your CMOS Setup and remove the entries for your EIDE hard drives after you remove them from the primary EIDE channel. Make sure you enter "none" or "not installed". The SCSI drives that you install do not need CMOS entries, and since there are no EIDE boot devices, the SCSI BIOS will allow your first SCSI hard drive (SCSI ID0) to be bootable. The most you might need to do with your CD-ROM drive would be to change its drive letter in MSCDEX (depending on how you partition the SCSI drives).
Mixing EIDE and SCSI devices is a bit more challenging. Yes, you can
mix EIDE and SCSI devices because they use two totally separate controllers.
When EIDE drives are in the system, your motherboard BIOS will attempt
to boot from an EIDE drive before booting from a SCSI device. This
isn’t a problem if you want to boot from EIDE, but can be a real
pain if you want to boot from a SCSI drive. The only real way around
this snafu is to use a SCSI controller with a SCSI BIOS that overrides
the motherboard BIOS and allows SCSI devices to boot. This may require
you to upgrade some older SCSI controllers.
Formatting Harddrive
Q: I am installing a new harddrive which needs to be formatted.
When I run FDISK and it ask for a certain drive how do I know I won't select
the wrong drive and format C? I need to format the D drive and work
from C. When FDISK ask do you want to format Drive 1 or Drive
2 how do I know which is 1? Also I am going to partition the new
drive into 2 partitions due to my computer not being able to handle
drives larger than the 528 MB. Any suggestions here. The new
drive is 1.2 GB.
A: First: check for the manufacturer's site for a BIOS upgrade that might allow support for bigger hard drives.
Second: several hard drive manufacturers offer
software with their drives that allows using them on older systems.
Like Quantum and Ontrack Disk Manager
http://support.quantum.com/menus/soft_menu.htm
Third: Once the hard drive is correctly recognized
and set up, you need to partition the hard drive using FDISK.
Fourth: The master drive (that you see as C:) is
drive 1, the slave drive drive 2. Master/slave relationship is defined
by
jumpers on the drive.
Fifth: Partitions are logical entities, unlike physical drives, though they are regarded as drives by the operating system.
Sixth: Formatting can be applied to partitioned drives.
The MSDOS utility format.exe facilitates it by formatting the disk to size
corresponding to the partition size as long as that size doesn't exceed
the capabilities of the DOS version. You
can get a lot of relevant information at e.g. http://support.quantum.com/faq/ATAFAQ.HTM
but it would be advisable for
you to check the site of the manufacturer of the specific hard drive
you have.
FDISK
Q. I'm having all kinds of trouble with FDISK. Every time I try to
partition my drive, the system hangs up, or I see a message like;
"Runtime error". What does that mean?
A. FDISK requires access to the drive's boot sector and master boot
record at track 00. FDISK errors almost always indicate corruption or damage
to track 00 which can render the entire drive unuseable. If your drive
has come
with a low-level format utility or specific track 00 diagnostic (typically
placed on the diskette which accompanied your drive), try that utility
and see if it clears the problem. If not, the drive may be defective,
and should be replaced.
Drive Letter
Q. I want to add a hard drive to my new system which includes a 2.5GB
hard drive partitioned as C: and D:. When I installed the new hard drive
in my system, the drive letters are changed around. The D: partition on
the old drive
becomes E:. Can I change drive letters, or can I install without this problem?
A. EIDE hard drives are all BIOS-supported, and all DOS-based operating
systems (including Windows) assign drive letters to the "Primary DOS"
partitions first, then the "Extended" partitions are assigned drive letters.
DOS will not allow you to change drive letters. The only way to get
the drive letters to read in order is to create only "Extended" partitions
on the new drive. This is not a difficult thing to do, and it will
not compromise your system's performance. However, there is a drawback
to creating only Extended partitions on the secondary drive - should
you ever decide to make the secondary drive a primary or only
drive in the system, you will NOT be able to boot to the drive. Since DOS-based
operating systems can only boot to a primary DOS partition, you would have
to repartition that new drive.
FDISK/MBR
Q. I'm in the process of upgrading my hard drive to one of those new
Maxtor 3.2GB CrystalMax drives. The problem is that I'm not sure where
to use FDISK. A friend told me to type FDISK /MBR. What's the difference?
Can you help clarify this?
A. It actually sounds like you've got a few different issues rolling
around there, so let's start from the beginning. Even after you physically
install a new hard drive, you've got to prepare the drive so that
your operating system (like our old friend MS-DOS) can determine just how
all that data is organized. There are actually three steps to that
"organizing" process; low-level formatting, partitioning with FDISK, and
DOS formatting with FORMAT.
You don't need to worry about low-level formatting today--it's all
done right at the factory. So after the drive is connected, you'll need
to partition it, and that's where FDISK comes in. The FDISK utility
lets you create one or more "logical" drives on your same physical
hard drive. For example, you could use FDISK to make a 2.0GB partition
and a 1.2GB partition on that same drive. You need to make the first
partition active and bootable so that your PC will be able to start from
there. So when you finally look at the drive under DOS (or Windows),
you'd see a C: drive and a D: drive (even
though they are both on the same hard drive). Of course, you could use
different sizes if you wish, and FDISK will support up to four partitions
on the same drive. Just remember that you can only create partitions up
to 2.1GB with the current versions of DOS and Windows 95, so for your 3.2GB
drive, you WILL need at least
two partitions.
Now let's talk about /MBR. That's actually a special "command line switch" that can be used with FDISK. The /MBR switch tells FDISK to recreate the drive's Master Boot Record&emdash;the vital information that your PC needs in order to boot from the hard drive. But the /MBR switch will prevent FDISK from recreating a whole new partition. When you run FDISK and create a new partition normally, the master boot record is rewritten automatically, so you do NOT need to use the /MBR switch when preparing a new drive. The time you want to use /MBR is when the master boot record has been corrupted due to problems like computer viruses or software bugs.
One final note: ideally, you should be able to use /MBR to restore the
master boot record without damaging any of the other data on your
drive&emdash;that's not always the case. You should always backup
your hard drive before working with partitions or formats. Otherwise, you
risk loosing your data.
Error Message
Q. I just installed my new Western Digital Caviar drive, and entered
the drive parameters in the CMOS, but the drive will not boot. It
displays the message; "HDD controller failure". Why is that?
A. You have not prepared the new hard drive correctly. Proper CMOS settings
are just the first step. You will need to boot the system from a floppy
diskette and run FDISK to partition the drive (remember to make your main
partition bootable and active). Next, use FORMAT to prepare the partition
for DOS. Finally, run the SYS utility from your floppy diskette (such
as: SYS C:) to place the required boot files on the drive. Your hard drive
should now be
bootable.
What you need to know about hard drive interfaces
A hard drive is connected to the host computer by way of an interface
- a controller card plus a cable and some software protocols. There are
two dominant types of hard drive interfaces available today: IDE and SCSI.
If you're adding a new hard drive, internal or external, you need to make
sure its interface matches that of your computer.
The term IDE stands for integrated drive electronics. Some vendors use the term AT attachment (ATA) to describe their IDE hard drives; ATA is the actual interface specification for the IDE standard. IDE is used almost exclusively on PC compatibles, largely because it is reasonably fast and requires inexpensive controller cards. Newer hard drives may come with EIDE (Enhanced IDE) interfaces. EIDE is much faster than plain IDE but requires additional hardware to work with the older ISA-bus desktop systems (newer PCI bus systems have built-in EIDE support).
SCSI (Small Computer Systems Interface) is used as a standard on Macintoshes as well as higher-end PCs such as network servers and power workstations, and is capable of far faster transfer rates than IDE or EIDE. SCSI-2 is a faster form of SCSI that comes in Fast, Wide, and Fast Wide versions, each with varying throughput rates. SCSI-2 is backwards compatible with SCSI: you can plug a SCSI device into a SCSI-2 port, but not vice versa. Finally, SCSI-3 is the fastest SCSI iteration to date, and comes in Fast, Wide, and Ultra versions, plus combinations of those three.
If you have a Macintosh, SCSI support is built right in; PC owners will usually have to invest in a SCSI controller card (around $100-200). If you're buying a SCSI drive, you need to make sure your controller card supports the correct version of SCSI. While it's easier to stick with the SCSI version your system supports, you can always upgrade to a new controller board that supports a faster SCSI speed.
You'll find some hard drives that connect via the parallel port. These can be used with portable computers for traveling, or with a desktop PC as extra storage space. Another portable alternative, PCMCIA (Personal Computer Memory Card International Association) is a credit-card sized version of IDE used in PC Cards.
Other interfaces Three types of serial SCSI, a new kind of SCSI interface, are also available but not yet widespread: SSA (serial storage architecture), FC-AL (fibre channel -- arbitrated loop), and IEEE-1394 (Apple's FireWire). A fourth serial technology, FC-EL (fibre channel -- enhanced loop), is a planned hybrid of SSA and FC-AL but won't become a reality until late this year at the earliest.
SSA, FC-AL, and FireWire have the ability to share multiple storage devices (and other types of devices) among multiple Macs and PCs. SSA and FC-AL max out at a full 127 devices per setup; FireWire can handle 63.
There are a few other interface types that you may see. MFM, RLL, and
ESDI are older interfaces that have been rendered largely obsolete by IDE/ATA
and SCSI.
SOURCE: Zdnet and Computer Currents