Download 5 - Parent Directory

Hardware Information
transmitting, and will back off and try again a little later. (You can see a
log of this activity in the DECnet NCP network counters.)
DECnet provides its own flow control, above and beyond the flow control
of the physical layer (if any). The end nodes handshake at the beginning
to establish a transmit window size—and a transmitter will only send
that much data before stopping and waiting for an acknowledgement.
The acknowledgement is only sent when the receiver has confirmed the
packet is valid. (A well-configured DECnet generally avoids triggering
any underlying (out-of-band) flow control mechanism.)
14.29
CD and DVD device requirements?
Read access to DVD-ROM, DVD+R/RW, DVD-R/RW, CD-ROM, and
CD-R/RW devices on ATAPI (IDE) connections is generally handled
transparently by SYS$DQDRIVER, and SYS$DQDRIVER will
transparently de-block the media-native 2048 byte disk blocks with the
512-byte blocks expected by OpenVMS and by native OpenVMS software.
Read access to DVD-ROM, DVD+R/RW, DVD-R/RW, CD-ROM,
and CD-R/RW devices on SCSI is handled by DKDRIVER, though
SYS$DKDRIVER will not transparently de-block the native 2048-byte
disk blocks into the 512-byte blocks expected by OpenVMS. The drive
or external software is expected to provide this de-blocking, thus either
a 512-byte block capable drive (such as all RRD-series SCSI CD-ROM
drives) is required, or host software is required for a 2048-byte block
drive. Third-party SCSI drives with UNIX references in their support
documentation or with explicit 512-byte selectors or swiches will generally
(but not always, of course) operate with OpenVMS.
At least some of the Plextor PlexWriter SCSI drives can be successfully
accessed (for read and write) from OpenVMS, as can at least one Pioneer
SCSI DVD drive (for CD media). The Pioneer SCSI DVD drive switches to
2048 byte blocks for DVD media, and a block-size conversion tool (written
by Glenn Everhart) or other similar tool can be applied.
OpenVMS also has supported HP DVD drives for the ATAPI (IDE) bus.
For some related information (and details on a commercial DVDwrite
package), please see:
•
http://home.tiscali.de/dvd4openvms/supported_hardware.html
No device driver currently presently permits direct block-oriented
recording on DVD-RAM nor DVD+RW media, nor other recordable or
rewritable media.
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