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Hard Disk Drive Transfer Protocols

Transfer Protocols Associated With EIDE:

There are several transfer protocols associated with an EIDE interface. They are: primary and secondary EIDE, Ultra DMA (ATA-33), and Ultra DMA (ATA-66). The fastest transfer protocol by far is the Ultra DMA (ATA-66) capable of theoretically transferring data at speeds of up to 66 MB/second. The slowest of all protocols is the primary EIDE protocol which transfers data at a maximum theoretical speed of 13 MB/second.

In the OSR2 version of Windows 95, Ultra DMA requires the drivers to be installed correctly. Ultra DMA is completely supported under the Windows 98 operating system.

Industry Standards

ATA (AT attachment) - standard, which determines physical, electrical, transport and command protocols for data storage devices connection with the main system (computer), which has been applied in personal computers since 1989. The development of the standard is carried out by NCITS committee (National Committee for Information Technology Standards) - T13. The standard is confirmed by NCITS, as well as on behalf of ANSI (American National Standards Institute). New versions of ATA/ATAPI support compatibility with previous ones providing opportunity for the connection of all devices compatible with ATA/ATAPI. Hard disk drives manufacturers often produce models which support either functionality in spite of the fact that it has not officially approved in the standard yet.

Was canceled in 1999.

PIO-4 and Multiword data transfer protocols DMA-2, block data transfer, logical blocks addressing (LBA), additional signals (IORDY, CSEL), engine shutdown commands, capability of data transfer control by CRC algorithm. Was canceled in 2001.

SMART and support of the access restriction. The LBA mode became required. Was canceled in 2002.

HPA (protected data area), "enhanced security erase", APM (advanced power-saving), commands overlapping, command queuing optimization (TCQ), Ultra DMA-2 protocol (33 MBytes/s), ATAPI (ATA Packet Interface) - the standard created in order to provide the opportunity of CD-ROM connection to the standard ATA connector that has simplified connection to CD-ROM and has made it possible to reduce their cost. The obsolete commands were deleted - "Format track", "Read/Write long", "Write verify".

Ultra DMA-3 (44 MBytes/s) and Ultra DMA-4 (66 MBytes/s) protocols.

Support of volume greater than 128 МBytes provided by increasing LBA size from 28 to 48 bits, Ultra DMA-5 (100 MBytes/s) protocol, commands of audio/video streams support (increased volume of information passed by one command from 131 KBytes to 33 MBytes), AAM (automatic acoustic management), extended SMART journals, deletion of CHS addressing.

Ultra DMA-6 (133 Mbytes/s) protocol, extended SMART self-testing modes (Selective, Conveyance), support of extended SMART journals, version of ATA series interface - SATA.

Trusted computing feature, free fall sensor, "Write-Read-Verify" feature, additional hard disk drive parameters management and enhanced data reading protocol (SCT Command Transport), flash memory with power-saving management capability (NV Cache, NV Cache Power Mode), nominal spindle motor rotation rate, time to spin up of the magnetic plates to the nominal velocity in seconds, WRITE UNCORRECTABLE EXT command.

Maxium Throughput of ATA DataTransfer Protocols

The maximal throughput of data transfer protocols is shown the table below.

Protocol ID mbps*   Protocol ID mbps*
PIO-0 3.3 Ultra DMA-1 25
PIO-1 5.2 Ultra DMA-2 33,3
PIO-2 8.3 Ultra DMA-3 44,4
PIO-3 11.1 Ultra DMA-4 66,7
PIO-4 16.7 Ultra DMA-5 100
Multiword DMA-0 4.2 Ultra DMA-6 133
Multiword DMA-1 13.3 SATA-1 150
Multiword DMA-2 16.7 SATA-2 300
Ultra DMA-0 16,7 SCSI 320
Table 1.2 - The Maximum Throughput of Various Transfer Protocols
* these values are represented as megabytes.










Requirements for the UDMA Transfer Protocol:

There are certain requirements that a system needs to meet to ensure the Ultra DMA interface is running properly. They are as follows:

  1. The hard disk must be the Ultra DMA type.
  2. The system board must have a chip set, which supports Ultra DMA, such as 82430TX or 82440LX.
  3. BIOS must "log on" the hard disk with Ultra DMA protocol. You can verify that in the start up screen.
  4. Drivers for the chip set must be installed in Windows 95.

SCSI Identification

SCSI Chain Of Command Identification SystemTo ensure that two SCSI devices are not using the same identification number, all SCSI devices, require a unique address (always labeled ID0 through ID7). The typical SCSI2 system can handle 8 devices and the SCSI Wide system handles 15 devices. SCSI devices can be internal or external, as a SCSI system always has at least one external connector on the controller itself. The typical SCSI chain is shown to the right. As already noted, each SCSI device within the system must have a different SCSI address, meaning that 2 SCSI devices cannot share a SCSI ID # such as SCSI-ID 2. A jumper or dip switch is typically used on the device itself to change its identification number. One final thing to remember about SCSI devices, is that the hard drive typically always occupies ID # 0 on the SCSI chain.

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