Increased SCSI Performance
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With the AIC-7890 and AIC-7891 single-chip host adapters, performance takes a giant leap forward.
Ultra2 technology doubles Ultra SCSI data transfer rates-up to 40 MByte/sec in 8-bit mode and up to
80 MByte/sec in 16-bit mode.
In addition, the AIC-7891 single-chip host adapter features a 64-bit PCI interface. This interfaces
doubles the PCI bandwidth and will address the needs of next generation 64-bit workstations and
servers.
These host adapters integrate several other performance-enhancing features. A 20-MIPS
PhaseEngine® RISC processor off loads I/O command processing from the system CPU. And the
data FIFO buffer is doubled to 512 bytes for more efficient PCI bus utilization.
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Longer Cables
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Using Low Voltage Differential (LVD) technology, these Ultra2 SCSI single-chip host adapters can
support up to a maximum of 15 devices on a 12 meter cable. This represents a fourfold increase over
UltraSCSI cable length. In a point-to-point configuration, cabling can be extended up to 25
meters. The increased cable length provides greater flexibility in system configuration, especially in
clustering and RAID applications.
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Backward Compatibility
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The AIC-7890 and AIC-7891 incorporate an advanced multimode I/O cell that supports both
single-ended and Ultra2 devices. With Ultra2 devices, the SCSI bus performs at full Ultra2
speeds and extended cabling. When a single-ended device is attached, the bus defaults to
single-ended speed and cable length.
In mixed environments of Ultra2 and single-ended devices, the AIC-7890 and AIC-7891 host adapters
can be coupled with an Adaptec AIC-3860 transceiver chip to bridge the compatibility gap. By dividing
the SCSI bus into independent single-ended and LVD segments, the AIC-3860 supports legacy devices
without limiting performance and cable length on the LVD segment. (see figure)
Ultra2 SCSI uses the same connectors and cables as UltraSCSI, so upgrading is easy and cost
effective.
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AIC-33C93B SBIC ARCHITECTURE
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![Figure](http://graphics.adaptec.com/aic7890_diagoem.gif) |
Optimizing performance in a mixed Ultra2 and single-ended peripheral configuration.
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Performance
PCI interface
- AIC-7890: 32 bit
- AIC-7891: 64 bit
Up to 80 MByte/sec on the Ultra2 SCSI bus
- Up to 40 MByte/sec data transfer rate in 8-bit mode
- Up to 80 MByte/sec data transfer rate in 16-bit mode
20-MIPS PhaseEngine RISC processor for SCSI command processing
512-byte data FIFO buffer for efficient PCI bus utilization
Cache line streaming for improved PCI bus utilization
Dual Address Cycle (DAC) on the AIC-7890 chip and AIC-7891 provides greater system memory addressability
Target mode to support clustering, bridge and RAID applications
Tagged command queuing allows changes in the order of SCSI command execution to improve performance
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Additional Features
Advanced multimode Ultra2 SCSI I/O cell for supporting single-ended or Ultra2 devices
JTAG boundary scan to support system level interconnect testing 3.3V / 5V PCI interface for providing flexibility for designing
high-performance, low-power systems
Enhanced Logical Unit Number (LUN) supports up to a maximum of 32 LUNs
ARO-1130 series support and RAIDport II compatible
Microsoft® Windows NT® Wolfpack clustering compatible
I2O-ready system compatible
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Software Support
Microsoft Windows NT, Windows® 95, Novell NetWare, SCO Openserver, SCO UnixWare, IBM OS/2,
and Sun Solaris
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SCSI Device Support
Connection for up to 15 SCSI devices
Support for a combination of 8-bit and 16-bit Ultra2, Ultra, and standard SCSI devices including
disk drives, tape drives, CD-ROM and CD-Recordable drives, jukeboxes, removable drives, scanners,
printers, and disk arrays.
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