Service Procedures
Digital PRIORIS ZX Server
60
MCS Logistics Engineering - Nijmegen
Mass Storage Devices
The server has three drive bay areas. Mass storage devices such as SCSI hard disk drives, floppy diskette
drives, SCSI CD-ROM drives, and SCSI tape backup systems are installed in these drive bay areas.
The three drive bay areas are:
♦
Left-front access drive bay area—This area has one 5¼-inch SCSI CD-ROM drive and one 3½-inch
diskette drive (standard on all Prioris ZX 5000 MP Series Servers).
♦
Top-right front access drive bay area—This area has room for two wide (68-pin) or narrow (50-pin)
5¼-inch or 3½-inch half-height SCSI devices or one full-height, 5¼-inch device .
♦
Lower-right front access drive bay area—This area has room for seven 3½-inch, wide or narrow Fast
SCSI-2, hot-swap devices.
Onboard SCSI Controllers
The main logic board includes two Adaptec
AIC-7870 wide/fast SCSI-2 controller chips
channels A
and B
integrated as PCI bus masters. These controllers support data path widths of 8-bit (narrow SCSI) at
a data transfer rate of 10 MB/sec and 16-bit (wide SCSI) at a data transfer rate of 20 MB/sec. As PCI bus
masters, these controllers support data transfer rates of 133 MB/sec.
You can connect up to seven 8-bit narrow SCSI devices or up to fifteen 8-bit fast and/or 16-bit wide SCSI
devices (as long as no more than seven 8-bit fast devices are used), with one controller to each channel.
For example, tape drives, printers, optical media drives, and other devices.
The SCSI controller provides active negation outputs, controls for external differential transceivers, a disk
activity output, and a SCSI terminator power-down control.
Active negation outputs reduce the chance of data errors by actively driving both polarities of the SCSI bus
and avoiding indeterminate voltage levels and common-mode noise on long cable runs. The SCSI output
drivers can directly drive a 48 mA, single-ended SCSI bus with no additional drivers.
No additional logic, termination, or resistor loads are required to connect up to seven 8-bit narrow SCSI
devices or up to fifteen 16-bit wide SCSI devices to each SCSI-2 channel on the main logic board.
