Ultra Ata - Compaq Deskpro AP400 Supplementary Manual

W P
HITE APER
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U ATA
L T R A
The Professional Workstation AP400 offers 6.4-GB Ultra ATA hard drive models in
addition to SCSI hard drive models. Ultra ATA is a definition for an ATA data transfer
protocol. The Ultra ATA protocol is included in the ATA-4 specification, an industry-
wide specification designed to provide firm guidelines to hardware developers and
manufacturers. The development of the transfer protocol "Ultra ATA" hard drives (also
known as UDMA, UATA, Ultra DMA, Ultra DMA-33) has increased the burst data
transfer rate to 33.3 MB/s compared to Fast ATA, effectively doubling the transfer rate
versus Fast ATA. Because of the faster transfer rates, Ultra ATA technology can process
the data twice as fast and therefore cut the time to empty the buffer from 250 ms to 125
ms. This savings in time allows the time to empty the buffer (400 ms) to equal the
buffer fill time, thus eliminating the bottlenecks experienced with Fast ATA.
CUSTOMER BENEFITS
Extends the data transfer rate. Provides improvement over Fast ATA
speed of 16.6 MB per second to 33.3 MB per second.
Provides improved signal integrity through CRC (Cyclical Redundancy
Check). Checks to verify the integrity of the data transferred by validating
all data transferred across the cable.
Fully backward compatible. Uses the same electrical connection as Fast
ATA, and can run in standard EIDE mode with old ATA chipsets. Ultra
ATA devices can also operate on an ATA bus with non-Ultra ATA devices.
Q. Why does the Compaq Professional Workstation AP400 use Ultra ATA
drives as well as Wide Ultra SCSI drives?
The Compaq Professional Workstation AP400 will attract different users. Some
A.
may need the higher speed 40-MB per second data transfer rate of Wide-Ultra
SCSI for extra performance. For those who find the 33.3-MB per second data
transfer rate satisfactory, Ultra ATA drives provide excellent price/performance,
with almost no difference when using business productivity applications.
Compaq Workstations - Key Technologies
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