Frequently Asked Questions Q: What is Ultra ATA/66?A: System requirements must be met in order for the drive to operate at peak capacity. The following information is for reference on the Ultra ATA/66 technology only.
Ultra ATA/66 is a low cost extension of the Ultra ATA/33 hard drive interface that doubles its burst data rate. Also known as Ultra DMA/66 and Fast ATA-2, Ultra ATA/66 allows host computers to send and receive data at 66.6 MB/s, which is twice the data transfer speed of 33.3 MB/s of Ultra DMA/33. The result is maximum disk performance under PCI local bus environments.
At its fast burst data rate, Ultra ATA/66 gos farther than Ultra ATA/33 in removing bottlenecks associated with data transfers, especially during sequential operations. Ultra ATA/66 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/33, CRC ensures the integrity of transferred data.
Newly introduced hard disks will support Ultra ATA/66 in the fourth calendar quarter of 1998. However system requirements must be met in order to utilize the technology. They transmit and receive data at higher rates and, thereby, provide better performance. Ultra ATA/66 is endorsed by all leading hard drive manufacturers as well, including Western Digital, Fujitsu, IBM, Maxtor, Quantum, Seagate, Toshiba and others. The protocol is also endorsed by chipset and motherboard vendor Intel with full industry support expected in 1999. The cooperative approach taken by these companies should smooth the path for standards adoption and compatibility.
Ultra ATA/66 hard disks are 100 percent backward compatible with Ultra ATA/33 and DMA, existing EIDE/IDE hard disks, CD-ROM drives, and host systems. The hard drive industry is expected to support Ultra ATA/66 in its new products for 1999.
By increasing the burst transfer rates of IDE drives, Ultra ATA/66 brings the effective transfer rate of the systems bus and a drives internal data rate that much closer into balance. Ultra ATA/66 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.
With continued expansions in disk capacity and higher rotational speeds, the hard drives 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/33 or the older multi-word DMA interfaces. Performance 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/66 can achieve.
As previously mentioned, fast host data transfer rates help maintain sequential media transfers, 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/66 Further Improves Transferred Data Integrity
The progressive advantage of Ultra ATA/66 is to double the transfer rate once again, this time by reducing setup times. Timing signals are made twice as fast. 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 44.4 MB/s or 66.6 MB/s burst rate. The 80-conductor cable retains the same connector configuration as the standard 40-pin interface cable but has ground lines interleaved between all 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/66 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 registers 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/66. 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.
Hard drives that support Ultra ATA/66 also support Ultra ATA/33 and multi-word DMA, and can be used with existing multi-word DMA host chipsets. Existing PCs without Ultra ATA/66 capability can use new hard disks in legacy ATA modes at transfer rates up to 33.3 MB/s. However, by upgrading with an Ultra ATA/66 PCI adapter card and 80-conductor cable, users can also take advantage of the interfaces newer speed and data integrity features. Bus timings must be scaled to transfer up to twice as fast.
PC vendors who would like to incorporate the advantages of Ultra ATA/66 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/66, the chipset pin count remains the same at 40.
System Requirements for Ultra ATA/66
Western Digitals Future Hard Drives
With Ultra ATA/66, data integrity takes another leap forward, especially when coupled in Western Digital hard disks with Data Lifeguard, an exclusive Western Digital feature that automatically detects, isolates, and repairs problem areas on hard disks 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 Digitals 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.
Western Digitals high-performance hard disks will soon incorporate the Ultra ATA/66 interface. Together with Data Lifeguard, the Ultra ATA/66 feature will enable Western Digitals new hard disks not only to provide maximum disk performance under PCI local bus environments, but also to furnish the highest data integrity possible.
Frequently Asked Questions
Information in this document was provided by the manufacturer.