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Ultra ATA/100 Extends Existing Technology
While Increasing Performance and Data Integrity
High-Speed Hard Drive Interface Increases the Ultra ATA/66 Burst Transfer Rate to 100 MB/s
Overview/Executive Summary
PC performance increases steadily from year to year due to the constant development of
high-speed microprocessors. As microprocessors become faster and faster, a corresponding
increase in data transfer rates between hard drives and system memory is required. For
desktop and portable computers, the Advanced Technology Attachment (ATA) interface is
the most popular protocol for moving data between the hard drive controller and system
memory.
Ultra ATA/100 is the latest version of the ATA hard drive data transfer protocol. A low-
cost extension of the Ultra ATA/66 hard drive interface, Ultra ATA/100 increases burst
data rates significantly over previous iterations of the protocol. Also known as Ultra
DMA/100 and Feature ATA, Ultra ATA/100 allows host computers to send and receive
data at 100 MB/s--considerably faster than the 66.6 MB/s data transfer speeds of Ultra
ATA/66. The result is maximum disk performance under PCI local bus environments.
At its fast burst data rates, Ultra ATA/100 will go farther than Ultra ATA/66 in removing
bottlenecks associated with data transfers, especially during sequential operations. Ultra
ATA/100 also delivers heightened data integrity to the EIDE interface through use of a
40-pin 80-conductor cable, and CRC (Cyclic Redundancy Check) error detection code.
The 80-conductor cable reduces crosstalk and improves signal integrity by providing 40
additional ground lines between the 40-pin IDE signal and ground lines. The connector
is plug-compatible with existing 40-pin headers, and the incremental cost for the cable
should be minimal. As with Ultra ATA/66, CRC ensures the integrity of transferred data.
40-Conductor Cable 80-Conductor Cable
40-pin IDE Interface
Figure 1. Ultra ATA/100 40-Pin, 80-Conductor Cable
Newly introduced Western Digital hard drives support Ultra ATA/100. They transmit and
receive data at higher rates, and thereby provide better performance. The Ultra ATA/100
protocol is also endorsed by the industry's leading chipset and motherboard manufacturers.
Ultra ATA/100 hard drives are 100 percent backwards compatible with Ultra ATA/66,
Ultra ATA/33, and DMA, as well as with existing EIDE/IDE hard drives, CD-ROM drives,
and host systems.
Background
Ultra ATA/100 is the latest ATA/IDE hard drive data transfer protocol for moving data
between the hard drive buffer and the system memory. The previous interface was
Ultra ATA/66, with a maximum burst transfer rate of 66.6 MB/s. Prior to Ultra ATA/66 was
Ultra ATA/33 with a maximum burst transfer rate of 33.3 MB/s.
By increasing the burst transfer rates of IDE drives, Ultra ATA/100 brings the effective trans-
fer rate of the system's bus and the drive's internal data rate that much closer into balance.
Ultra ATA/100 allows system designers to provide greater system throughput, particularly for
long sequential transfers required by audio/visual applications.
Host data transfer rates must exceed media data transfer rates or else performance is reduced
because of additional revolutions due to buffer full/empty conditions on reads/writes. The
following chart plots the media data transfer rates over time (represented by the trendline),
thus indicating the need for ever-higher host data transfer rates (represented by the shaded
area).
120
100
Megabytes per Second (MB/s)
80
60
40
20
0
1994 1997 1999 2000
MB/s 16.6 33.3 66.6 100
Figure 2. Host and Media Data Transfer Rate Increase Over Time
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As demonstrated in "Figure 2. Host and Media Data Transfer Rate Increase Over Time" on
page 2, the industry has supported host transfer data rates doubling previously:
Host Transfer Data Rate Increase
Mode Rate Year of Introduction
DMA Mode 2 16.6 MB/s 1994
Ultra ATA/33 33.3 MB/s 1997
Ultra ATA/66 66.6 MB/s 1999
Ultra ATA/100 100 MB/s 2000
With continued expansions in disk capacity and higher rotational speeds, the hard drive's
internal disk rates also continue to increase. The transfer of large files, often written
sequentially on the hard drive, is particularly affected by the transfer rate. During sequential
reads, the hard drive, because of its fast internal data rate, may fill its buffer faster than the
host can empty it when using the Ultra ATA/66 or the older multi-word DMA interfaces. Per-
formance bottlenecks usually result in this connection between the host and the hard drive.
Improving the interface to keep up with internal data rate improvements is exactly what Ultra
ATA/100 achieves.
As previously mentioned, fast host data transfer rates help maintain sequential media trans-
fers, but they also accelerate cache hits. The following table is based on all commands being
either a cache hit (data comes from the buffer and has <1 ms latency), or a cache miss (data
comes from the media and has >10 ms latency.)
Ultra ATA/100 Performance Benefit
Cache Miss Cache Hit
Sequential Yes Yes
Random No Yes
Ultra ATA/100 Further Improves Transferred Data Integrity
The way signaling was performed on the ATA bus up through multi-word DMA Mode 2
(16.6 MB/s) was to send data in synchronous strobe mode but on the positive transition of
the strobe signal only. The breakthrough Ultra ATA/33 extension was key to using both the
positive and negative transitions of the strobe signal, effectively doubling the available
transition frequency without actually increasing the frequency of the strobe. The result was to
double the burst transfer rate. By having the hard drive as the source of both the strobe and
the data during a read, Ultra ATA/33 eliminated both propagation and data turnaround
delays. The elimination of these delays improved the timing margins. Ultra ATA/100 retains
the same strobe frequency but increases the burst transfer rate three-fold over Ultra ATA/33.
The progressive advantage of Ultra ATA/100 is to increase transfer rates. However, a new
80-conductor cable is needed to ensure data integrity. The 40-pin interface cable of the earlier
Ultra ATA/33 and multi-word DMA interfaces cannot handle the shorter cycle times for a
66.6 MB/s or 100 MB/s burst rate. The 80-conductor cable retains the same connector con-
figuration as the standard 40-pin interface cable but has ground lines interleaved between all
-3-
signal lines. In other words, the 40 new lines are all ground (which act as shields) and no new
signals are transferred.
Ultra ATA/33 introduced CRC (Cyclical Redundancy Check), a feature new to IDE that
provides data protection verification. Ultra ATA/100 uses the same process. The CRC is
calculated on a per-burst basis by both the host and the hard drive, and is stored in their
respective CRC registers. At the end of each burst, the host sends the contents of its CRC
register to the hard drive, which then compares it against its own register's contents. If the
hard drive reports errors to the host, then the host retries the command containing the CRC
error.
No change in the Ultra DMA protocol is required for Ultra ATA/100. When the protocol is
used at speeds slower than 33.3 MB/s, both signal and data integrity still surpass that of
multi-word DMA and earlier protocols at a given burst transfer rate, providing even greater
data integrity margins.
Backward Compatibility
The Ultra ATA/100 protocol and commands are designed to be compatible with existing ATA
devices and systems. Drives implementing Ultra ATA/100 are fully backwards compatible
with older ATA modes, including Ultra ATA/66. It will handle all the data transfer modes.
The slower modes will be supported with a different clock signal and clock divider. The
slower modes previously worked with a standard 40-pin interface cable, but Ultra ATA/100
requires a 40-pin, 80-conductor cable for modes 3, 4, and 5.
Data Transfer Rate Cable Conductors CRC
(max.)
DMA Mode 1 11.1 MB/s 40-pin IDE 40-pin No
Multi-word DMA Mode 1 13.3 MB/s 40-pin IDE 40-pin No
Multi-word DMA Mode 2 16.6 MB/s 40-pin IDE 40-pin No
Ultra ATA Mode 2 33.3 MB/s 40-pin IDE 40-pin Yes
Ultra ATA Mode 2 44.4 MB/s 40-pin IDE 40-pin Yes
Ultra ATA Mode 4 66.6 MB/s 40-pin IDE 80-pin Yes
Ultra ATA Mode 5 99.9 MB/s 40-pin IDE 80-pin Yes
Hard drives that support Ultra ATA/100 also support Ultra ATA/66 and multi-word DMA,
and can be used with existing multi-word DMA host systems. Installed PCs without
Ultra ATA/100 capability can use new hard drives in legacy ATA modes at transfer rates up to
66.6 MB/s. However, by upgrading with an Ultra ATA/100 PCI adapter card, they can also
take advantage of the interface's newer speed and data integrity features.
PC vendors who would like to incorporate the advantages of Ultra ATA/100 in new systems
can do so by using new chipsets and motherboards from Intel and other leading vendors that
license the technology. Although a new cable is required for Ultra ATA/100, the chipset pin
count remains the same at 40.
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System Requirements for Ultra ATA/100
To use the Ultra ATA/100 technology, a system must have:
1. Ultra ATA/100 compatible logic either on the system motherboard, or on an Ultra DMA PCI
adapter card
2. Ultra DMA compatible BIOS
3. DMA-aware device driver for the operating system
4. Ultra ATA/100-compatible IDE device such as a hard drive or CD-ROM drive
5. 40-pin 80-conductor cable
Western Digital's Future Hard Drives
With Ultra ATA/100, data integrity takes another leap forward, especially when coupled in
Western Digital hard drives with Data LifeguardTM, an exclusive Western Digital feature that
automatically detects, isolates and repairs problem areas on hard drives to prevent data loss.
This continuous self-tuning process scans and repairs while the drive is idle. Data Lifeguard is
both an enhancement and an extension to Western Digital's S.M.A.R.T. (Self Monitoring,
Analysis and Reporting Technology) System that monitors and predicts the performance of
hard disk drives. Data Lifeguard works independently from S.M.A.R.T. to provide a
self-healing capability.
Together with Data Lifeguard, the Ultra ATA/100 feature enables Western Digital's new hard
drives not only to provide maximum disk performance under PCI local bus environments,
but also to furnish the highest data integrity possible.
Frequently Asked Questions
1. I have an Ultra ATA/33 system today. How can I support Ultra ATA/100?
An existing system can be upgraded by purchasing a PCI-EIDE controller that
supports Ultra ATA/100. For service and literature:
800.ASK.4WDC USA
2. Do Microsoft Operating Systems support Ultra ATA? 507.286.7900 Outside USA
www.westerndigital.com
Windows releases indicate that they all support DMA transfers. The Ultra ATA data
transfer rate is determined by your HDD, your controller, the BIOS, and the operating
system. This applies for all the following Windows operating systems: Western Digital and the
Western Digital logo areregistered
- Windows 95 OEM Service Release 2 and higher trademarks of Western Digital
Corporation. Other marks may be
- Windows NT Service Pack 3 and higher mentioned herein that belong to
other companies. Product
specifications subject to change
3. I don't have a system that supports Ultra ATA/100, can I run the Ultra ATA/100 HDD in it? without notice.
Yes, the HDD will not run in UATA/100 mode but instead is a slower compatible