Ultra ATA/66 — Breaking Speed Barriers Again
The Evolution of the
Ultra ATA/66 is the latest in IDE data transfer standards and, like the interface itself, is an inexpensive way to connect hard drives while still allowing high transfer speeds data. Like its predecessor Ultra ATA/33, it was proposed by Quantum and accepted by most manufacturers of drives and chipsets. Also known as Ultra DMA/66. Compared to Ultra ATA/33, Ultra ATA/66 doubles the data transfer rate limit between the hard disk cache buffer and the system bus — up to 66.6 MB/s, against 33.3 MB/s for Ultra DMA/33. Despite the fact that the limitations on the speed of disks are imposed primarily by their mechanical characteristics and the technology of manufacturing components, the task of electronics and data transfer protocol developers is to prevent the peak values of the internal data transfer rate between working surfaces from approaching through the heads to the internal cache of disks. with the limitations of silicon. With twice the headroom, Ultra ATA/66 guarantees, even more so than Ultra ATA/33, that disk and motherboard electronics will not be a bottleneck in data transfer, and especially in sequential read and write operations. In addition, Ultra ATA/66 provides data integrity, which is important for the EIDE interface, the disadvantage of which is poor noise immunity. For this, additional shielding is introduced, using a 40-pin 80-wire cable and error checking using a cyclic redundant CRC code (Cyclic Redundancy Check). In addition to the usual 40 signal and ground lines, another 40 ground lines reduce interference and improve signal quality. The connector is pin-compatible with existing 40-pin wiring, minimizing the extra cost of a new type of cable. nine0005
The previous Ultra ATA/66 data transfer protocol Ultra ATA/33 guarantees data streams with a maximum peak speed of 33.3 MB/s. In turn, before the advent of Ultra ATA / 33, its role was played by data transfer standards with the participation of the PIO Mode 4 central processor and packet packets with direct access to the DMA Mode 2 system memory with a maximum speed of 16. 6 MB / s. Ultra ATA/66 is twice the capabilities of Ultra ATA/33 and four times the capabilities of PIO Mode 4/DMA Mode 2. The development of the interface capabilities occurs at the signal level, by changing the specification for following data to the clock pulses. With the change in the mechanical parameters of modern hard drives, their rotation speeds, the improvement of head suspensions, the change in their type, material, and technology for applying a magnetic layer to the working surfaces of disks, the internal data transfer rate has noticeably increased, and will continue to grow further, more and more approaching the limits, set by the interface of the disk with the system bus. Ultra ATA/66 reasonably matches the effective transfer rate on the system bus with the internal speed of the drives. The new protocol makes it possible to guarantee a higher bus bandwidth, which is especially important for the modes of continuous serial data transfer typical for audio / video applications. nine0005
The data transfer rate to and from the system bus must exceed the internal speed of the surface, otherwise performance drops — additional drive revolutions are required to empty the buffer when reading from the surface and fill it when writing. You can fight this by increasing the size of the disk cache buffer or by increasing the efficiency of its exchanges with the system bus. The first method is associated with the use of expensive memory and contradicts the very purpose of IDE disks, manufacturers do their best to minimize the size of the cache. The graph below reflects the upward trend in the internal data rate, confirming the need to increase the interface rate. It follows that Ultra ATA/33 limits will be reached in the second half of 1999 years, which means the time for Ultra ATA/66 has come.
The graph confirms that the interface data rate is doubling every three years. Ultra ATA/66 will become obsolete somewhere by 2002. Previous milestones experienced by the industry were related to implementation:
- PIO Mode 4 and DMA Mode 2, 16. 6 MB/s in 1994
- Ultra ATA/33, 33.3 MB/s in 1997
- Ultra ATA/66, 66.6 MB /s in 1999
Continued increase in the capacity of disks and their rotation speeds, their internal speeds also continue to grow. Transferring large files, especially those written sequentially to disk, is especially sensitive to interface capabilities. With sequential reads, the disk, due to its high internal speed, can fill the buffer faster than the system reads data from it. The performance of the disk subsystem most often falls due to such bottlenecks. Ultra ATA/66 is a tool for improving the interface, which is relevant right now due to the change in the structure of transmitted information streams towards multimedia data. nine0005
Ultra ATA/66 Ensures Data Integrity
Standard ATA bus data transfer in the DMA Mode 2 specification (16.6 MB/s) consisted of bursts of data, clocked by pulses, but only on the rising edge of the strobe signal. The basic idea behind the Ultra ATA/33 expansion was to use both the rising and falling edges of the signal for synchronous data transfer, achieving double the data rate without increasing the pulse rate. Having a hard drive as a generator of both pulses and data in the process of reading, the Ultra ATA/33 specification eliminated delays in the data forward and reverse passage, which made it possible to improve the transmission timing diagram. Ultra ATA/66 uses the same strobe rate but again doubles the peak transfer rate possible, this time by reducing transfer mode entry times. Data clocking is twice as fast. However, a new 80-wire cable is required to ensure data integrity. A standard 40-pin, 40-wire cable can’t handle time loops at transfer rates of around 66 MB/s. An 80-wire cable will be used with the same 40-pin connector, but the signal lines in it will be separated by ground lines acting as a shield. No new signals will be generated or transmitted. nine0005
Ultra ATA/33 pioneered CRC error checking, a new option for the IDE interface for data verification. Ultra ATA/66 uses the same procedure: the CRC is calculated at the time of transmission by the host system and the hard disk, and the information is placed in the appropriate CRC registers. After each data packet, the host system sends the contents of the CRC register to the hard drive, which compares the received value with its own. In this case, in case of discrepancy, the transmitted data is requested again. nine0005
Compatibility and system requirements
The Ultra ATA/66 protocol and commands are compatible with existing ATA devices and systems. Drives implementing Ultra ATA/66 are fully backward compatible with previous ATA modes, including Ultra ATA/33. Slower modes will be served with different clocks and timing. When migrating a drive to a new standard system, you will need to replace the standard 40-pin interface cable with a new 40-pin 80-wire cable. The reverse is also true: for Ultra ATA/33 and older drives connected to systems whose logic is able to implement Ultra ATA/66, the data transfer rate cannot exceed 33 MB/s. Full implementation of the Ultra ATA/66 specification requires an appropriate drive, chipset, and new-style cable. (It should be noted that with UDMA/66 technology, both the PC and the hard disk check for the presence of an 80-wire cable, and without it, the disk subsystem will work in the old standard). For PCs that do not natively support Ultra ATA/66, it is possible to upgrade by replacing the drive with a new one, using an Ultra ATA/66 PCI adapter and a new cable. This will require scaling the timing characteristics to implement the new protocol. As far as support from the operating system is concerned, only the implementation of data transfer in DMA mode is required. Windows allows this, and does not make any difference whether data is transferred to Ultra ATA/33 or Ultra ATA/66. Transfer protocol speeds are determined by the HDD, controller and motherboard BIOS. The above is true for operating systems:
- Windows 98
- Windows NT Service Pack 3
- Windows 95 OEM Service Release 2
So, to use Ultra ATA/66 technology you need:
- Ultra ATA/66 compatible logic or on the motherboard Ultra DMA PCI adapter.
- Ultra DMA compatible BIOS
- DMA device driver for operating system
- Ultra ATA/66 compatible IDE device (hard drive, CD-ROM, etc. )
- 40-pin 80-wire cable
The Ultra ATA/66 interface is time for two reasons. The much-discussed transition to the IEEE 1394 high-speed serial bus (FireWire) and the transfer of disks in desktop systems to this interface has not yet passed into the stage of accepting specifications. In particular, Intel excluded the mention of 1394 from the development of the bridge part of its new PIIX6 chipsets, which indicates a delay in the implementation of this interface. At the same time, the continuous growth of typical data transfer rates in hard drives due to the increase in the linear density of recording on the surface and the acceleration of drives promises to end 1999 years to reach the limits of Ultra ATA / 33. To sustain performance growth, the interface speed limit must also increase. As a result, the industry is expected to support Ultra ATA/66 in 1999 with new products: Western Digital, Fujitsu, IBM, Maxtor, Quantum, Seagate, Toshiba and others.
Western Digital pioneered the Ultra ATA/66 standard among all storage manufacturers by equipping the latest family of Caviar EIDE drives with a capacity of 4.3Gb per platter (the older representative of the AC313000 is 13Gb) with Ultra ATA/66 electronics. Obviously, the corresponding products of competing manufacturers will appear in the very near future. Despite the fact that the drives of the first wave, equipped with new electronics, do not develop those speeds for which the introduction of the specification is critical, their appearance should be considered as the introduction and testing of the future standard. The situation was exactly the same with the advent of Ultra ATA/33. Until now, most drives not only do not approach its 33 MB / s limits, but even in peak mode do not exceed the DMA Mode 2 16.6 MB / s values, but the development and calculated behavior of new products is not constrained by electronics limitations. disks or system logic of motherboards. nine0005
As for support for Ultra ATA/66 at the system logic level, so far it has been implemented only by chipset developers alternative to Intel — VIA Technologies and Silicon Integrated Systems (SiS). Ultra ATA/66 — compatible chipsets are VIA MVP4 for Socket 7 and VIA Apollo Pro for Slot 1 (both include South Bridge VT82c596, responsible for supporting peripherals). SiS implemented support for the standard in the SiS 530 chip for Socket 7, which includes an Ultra ATA/66 IDE controller. Presumably, the BIOSes of motherboards developed on the basis of the new sets will allow working with the timing characteristics of the new specification. As for Intel, support for Ultra ATA/66 will be implemented in the PIIX6 controller, which will be part of the new i820 chipset in the second quarter. nine0005
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Ultra ATA/66 FAQ
Of all the properties of the Ultra ATA/66 interface, the main one today is… its name.
Once again, in a brief form of questions and answers, it is worth dwelling on what new features the Ultra ATA/66 interface has in comparison with its predecessors, what requirements it imposes on devices that implement it, and what a real user can get from it. nine0005
What is Ultra ATA/66?
Ultra ATA/66 is the latest evolution of the ATA/IDE hard drive interface. This is a set of specifications related to the electronics of hard drives and motherboards, and describes the signaling between the drive and the board. Without going into details, we can say that the definition of a “new high-speed interface” means that the timing diagrams formed using the new Ultra ATA / 66 signal protocols fundamentally allow data transfer at a speed twice as high as that achievable by its predecessor, Ultra ATA / 33. Ultra ATA/66 retains a cyclic redundancy code (CRC) data integrity check. In order to avoid signal distortions, the shielding of signal lines is introduced due to additional conductors of the connecting cable. Retaining the old 40-pin connector, the new cable is 80-wire, with most of the conductors connected to ground. nine0005
What is the difference between Ultra ATA/66 and Ultra ATA/33?
A compressed timing diagram that allows twice as much data to be transmitted over the new interface in the same period of time. The bandwidth limit has been doubled from 33 MB/s to 66 MB/s.
What is required from the system to work with the new interface?
- Ultra ATA/66-compatible logic on motherboard or dedicated Ultra DMA PCI adapter and Ultra DMA-compatible BIOS
- Ultra ATA/66 support by the hard drive itself. You may need to activate this mode (if this option is available by default, but disabled), for example, using the appropriate manufacturer’s utility.
- Drive connection must be made with a 40-pin 80-wire cable
- DMA device driver for the operating system used
Which of the existing motherboard chipsets support Ultra ATA/66?
For Slot1/Socket 370 architecture: i810 Whitney — in its more expensive modification with the i82801AA (ICH) controller as part of, SiS 620, VIA Apollo Pro Plus. For Socket 7 architecture: VIA MVP4, SiS 530.
Which manufacturers’ hard drives support Ultra ATA/66?
- IBM Deskstar 25GP 5400rpm and Deskstar 22GXP 7200rpm series;
- all new Western Digital drives: Caviar 5400rpm 4. 3-20.4GB and Expert 7200rpm 9.1-18.3GB series;
- Quantum Series Fireball CR 5400rpm 4.3-13GB, Fireball CK 5400rpm 6.4-20.4GB, Fireball Plus KA 7200rpm 6.4-18.2GB;
- Fujitsu series MPD3xxxAT 5400rpm 4.3 -18GB and MPD3xxxAH 7200rpm 4.55 -18GB;
- Seagate Medalist Series ST3xxx32A, STxxx42A, 5400rpm 10.2-17.2GB and U4, 7200rpm, 4.3-8.4GB
Why is there a need for a new 40-pin 80-core cable?
An increase in the information transfer rate is associated with a change in the frequency characteristics of the signals, and may be accompanied by interference between adjacent conductors. To avoid interference and maintain the integrity of the transmitted data, the existing 40 signal lines and ground lines in the new cable are interleaved with an additional 40 ground lines. A new cable costs a little more than a regular 40-core cable. nine0005
Is the Ultra ATA/66 interface downward compatible?
100% compatible, which means that Ultra ATA/66 hard drives can be used in systems where some or all of the components do not meet the prerequisites listed above. At the same time, the limits of the theoretically permissible data transfer rate over the interface remain at the same level — 33MB / s.
Can the new 80-core cable be used with an old drive/in an old system?
Yes, the new cable is downward compatible with the old 40-core cable. Performance is limited by the Ultra ATA/33 interface.
What can happen if the drive’s Ultra ATA/66 option is enabled, but the drive is running in a system that does not support this standard?
Usually nothing. The disk will perform as well as its physical capabilities and system limitations allow. There may be incompatibility with some older BIOS versions, which in rare cases can lead to slow performance or CRC transmission errors. Some manufacturers, such as Western Digital, recommend using a utility (WDATA66 for WD drives) to enable/disable Ultra ATA/66 mode in cases where drives are guaranteed to support the new standard, but there is no certainty that it will be supported by other system components. nine0005
What is the actual data transfer rate between the disk and the system bus?
The speed of information transfer in real conditions depends on many parameters: the characteristics of the disk itself, the location of data on it, the operation of applications and the operating system responsible for servicing the disk, etc. Usually, they talk about two threshold parameters: the internal data transfer rate between surface and working heads that send information to the disk cache buffer (Media to Buffer) and external speed — between the disk cache and the system bus (Buffer to Host). The first value is determined by physical parameters: the type of heads, the properties of the magnetic layer of the surface, the location of the tracks from which data is read. Peak surface read speeds for modern disks rarely exceed 160-200 megabits per second (i.e. 20-25 MB/s). The average reading speed from different tracks, interspersed with head positioning, is even less. At such speeds, no matter how fast the cache buffer communicates with the host system, it is not able to transfer more data per unit of time than it has in itself! For modern systems, we can talk about data transfer in a stream with a stable speed of about 10-12 MB / s, and then only for individual applications, such as reading / writing video or sound, working with data sequentially placed on a disk. Ultra ATA/66 describes Buffer to Host transfer modes, and its external speed limit of 66 MB/s is more of a theoretical limit to ensure that electronics capabilities don’t become a performance bottleneck for hard drives for the foreseeable future. nine0005
Why is the Ultra ATA/66 interface heavily advertised if it doesn’t provide speed gains?
Until now, most drives operate at speeds that are sufficient not only for Ultra ATA / 33, but also for earlier PIO Mode 4, DMA 2 protocols with their maximum bandwidth of 16 MB / s. If the internal speed of the disks increases gradually, as the technologies for manufacturing the working surface and components of the disks improve, then the external speed refers to the development of semiconductor circuits for accelerated signal transmission, it changes abruptly — in accordance with the agreements reached by the developers of the standard. At the time of implementation of new protocols, disks do not become faster. The main purpose of these agreements and their implementation in silicon is to prevent the convergence of typical internal and external disk speeds, when the limitations of electronics can become a limiting factor in performance growth. The new data transfer protocol is a new step that characterizes the progress in the industry and is rightly considered by the developers of hard drives and system logic as a landmark event. Nevertheless, it follows from the above that apart from the marketing effect and maintaining the manufacturer’s reputation as a conductor of progressive technologies, no real benefit for consumers from Ultra ATA/66 should be expected in the near future. nine0005
Do I need to buy a new Ultra ATA/66 drive in this case?
It is necessary, because there are practically no others.
May 31, 1999
New statistics based on the use of 230,000 hard drives.