HP Vectra VEi8 HP Vectra VEi7, VEi8 & VLi8, Technical Reference Manual (V - Page 22

Mass-Storage Devices, Ultra-ATA Hard Disk Drives

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Core Components and Technologies Mass-Storage Devices Mass-Storage Devices Ultra-ATA Hard Disk Drives ATA (AT Attachment) is a disk drive implementation designed to integrate the controller into the drive itself, thereby reducing interface costs. Ultra-ATA bridges the gap between the current standard (ATA-3) and the upcoming standard ATA-4. Ultra-ATA adds a new, high performance mode: DMA/33 with 33MB/s bandwidth, twice that of DMA mode 2. Ultra-ATA provides higher levels of disk throughput (with a burst transfer rate of 33 megabytes per second) yet also enhancing data integrity. A checksum is added to the data sent over the ATA interface. That way, data corruption can be detected and the data retransmitted. Ultra-ATA improves timing margins by eliminating propagation and data turnaround delays. During a read under Fast ATA, the drive must wait for the strobe from the host (propagation delay) before taking some time to respond by putting data on the bus (data turnaround delay) - for which the host must then wait (more propagation delay). All these events must occur with a fixed time window between the falling edge of the strobe and the rising edge, when data is latched in the host. The Ultra-ATA protocol eliminates these delays by having the drive be the source of both the strobe and the data during a read. Since the strobe and data signal travel in the same direction down the cable simultaneously, propagation delay in the opposite direction is eliminated. And since the drive controls both strobe and data, there is no data turnaround delay. With the time window remaining constant, less delay means improved timing margins during reads. 22

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Core Components and Technologies
Mass-Storage Devices
22
Mass-Storage Devices
Ultra-ATA Hard Disk Drives
ATA (AT Attachment) is a disk drive implementation designed to
integrate the controller into the drive itself, thereby reducing interface
costs. Ultra-ATA bridges the gap between the current standard (ATA-3)
and the upcoming standard ATA-4. Ultra-ATA adds a new, high
performance mode: DMA/33 with 33MB/s bandwidth, twice that of
DMA mode 2.
Ultra-ATA provides higher levels of disk throughput (with a burst
transfer rate of 33 megabytes per second) yet also enhancing data
integrity. A checksum is added to the data sent over the ATA interface.
That way, data corruption can be detected and the data retransmitted.
Ultra-ATA improves timing margins by eliminating propagation and
data turnaround delays. During a read under Fast ATA, the drive must
wait for the strobe from the host (propagation delay) before taking
some time to respond by putting data on the bus (data turnaround
delay) - for which the host must then wait (more propagation delay).
All these events must occur with a fixed time window between the
falling edge of the strobe and the rising edge, when data is latched in
the host.
The Ultra-ATA protocol eliminates these delays by having the drive be
the source of both the strobe and the data during a read. Since the
strobe and data signal travel in the same direction down the cable
simultaneously, propagation delay in the opposite direction is
eliminated. And since the drive controls both strobe and data, there is
no data turnaround delay. With the time window remaining constant,
less delay means improved timing margins during reads.