The OpenVMS Frequently Asked Questions (FAQ)

Previous Contents Index

14.27 What connectors and wiring adapters are available?

The H8571-B and H8575-B convert the (non-2000-series) MicroVAX DB9 to the DECconnect DEC-423 Modified Modular Jack (MMJ) pin-out; to the MMJ DECconnect wiring system. The MicroVAX 2000 and VAXstation 2000 requires a BCC08 cable (which has the 8-9 short, see Section 14.26) and the H8571-C or the H8571-D DB25-to-MMJ adapter for use with DECconnect. (For a discussion of the console bulkhead on the MicroVAX II series and on other closely-related series systems, please see Section

Somewhat less ancient HP (HP, Compaq or DIGITAL logo) systems will use either the DECconnect MMJ wiring directly or---on most (all?) recent system designs---the PC-compatible DB9 9-pin pin-out; the PC-style COM serial port interface and connection.

There are two DB9 9-pin pin-outs, that of the H8571-B and similar for the MicroVAX and other and older systems, and that of the H8571-J for the PC-style COM port, AlphaStation, Integrity, and other newer systems. The older MicroVAX DB9 and the PC-style DB9 pin-outs are not compatible.

Table 14-8 DECconnect MMJ Connectors and Adapters
Part Converts BC16E MMJ male to fit into
H8571-A EIA232 DB25 25-pin female (common). Functionally similar to the H8575-A, though the H8575-A has better ESD shielding.
H8571-B Older MicroVAX (other than the MicroVAX 2000) DB9 EIA232 serial port. Functionally similar to the H8575-B, though the H8575-B has better ESD shielding. Note: Cannot be used on a PC, Alpha nor Integrity DB9 9-pin connector.
H8571-C 25 pin DSUB Female to MMJ, Unfiltered
H8571-D EIA232 25 pin male (modem-wired)
H8571-E 25 pin DSUB Female to MMJ, Filtered
H8571-J PC, Alpha, Integrity 9 pin (DB9) male (PC-style COM serial port) Note: Cannot be used on the older MicroVAX DB9 9-pin connector
H8572-0 BC16E MMJ double-female (MMJ extender)
H8575-A EIA232 DB25 25-pin female (common). Functionally similar to the H8571-A, though the H8575-A has better ESD shielding.
H8575-B Older MicroVAX (other than the MicroVAX 2000) DB9 EIA232 serial port. Functionally similar to the H8571-B, though the H8575-B has better ESD shielding. Note: Cannot be used on a PC, Alpha nor Integrity DB9 9-pin connector
H8575-D 25 Pin to MMJ with better ESD Protection
H8575-D 25 Pin to MMJ with better and ESD Protection
H8575-E 25 Pin Integrity rx2600 Management Processor (MP) port to MMJ, with ESD Protection
H8577-AA 6 pin Female MMJ to 8 pin MJ
BC16E-** MMJ cable with connectors, available in various lengths

Numerous additional adapters and cables are available from the (now out of print) OPEN DECconnect Building Wiring Components and Applications Catalog, as well as descriptions of the above-listed parts.

The DECconnect wiring system has insufficient signaling for modems, and particularly lacks support for modem control signals.

The H8571-A and H8575-A are MMJ to DB25 (female) and other connector wiring diagrams and adapter-, cable- and pin-out-related discussions are available at:

Jameco has offered a USB-A to PS/2 Mini DIN 6 Adapter (as part 168751), for those folks wishing to (try to) use PS/2 Keyboards via USB-A connections.

The LK463 USB keyboard is also a potential option, for those wishing to connect an OpenVMS keyboard to USB systems or (via the provided adapter) to PS/2 systems. The LK463 provides the classic OpenVMS keyboard and keyboard layout on USB-based system configurations, including operations with the USB connection on specific Alpha systems (and specifically on those with supported USB connections) and on Integrity servers.

For information on the Alpha console COM port(s) or on the VAX console port, please see Section 14.3.

14.28 What is flow control and how does it work?

XON/XOFF is one kind of flow control.

In ASCII, XON is the [CTRL/Q] character, and XOFF is the [CTRL/S].

XON/XOFF flow control is typically associated with asynchronous serial line communications. XON/XOFF is an in-band flow control, meaning that the flow control is mixed in with the data.

CTS/RTS is another type of flow control, and is sometimes called hardware flow control. Out-of-band means that seperate lines/pins from the data lines (pins) are used to carry the CTS/RTS signals.

Both kinds of flow control are triggered when a threshold is reached in the incoming buffer. The flow control is suppose to reach the transmitter in time to have it stop transmitting before the receiver buffer is full and data is lost. Later, after a sufficient amount of the receiver's buffer is freed up, the resume flow control signal is sent to get the transmitter going again.

DECnet Phase IV on OpenVMS VAX supports the use of asynchronous serial communications as a network line; of asynch DECnet. The communication devices (eg. modems, and drivers) must not be configured for XON/XOFF flow control. The incidence of these (unexpected) in-band characters will corrupt data packets. Further, the serial line device drivers might normally remove the XON and XOFF characters from the stream for terminal applications, but DECnet configures the driver to pass all characters through and requires that all characters be permitted. (The communication devices must pass through not only the XON and XOFF characters, they must pass all characters including the 8-bit characters. If data compression is happening, it must reproduce the source stream exactly. No addition or elimination of null characters, and full data transparency.

An Ethernet network is rather different than an asynchronous serial line. Ethernet specifies the control of data flow on a shared segment using CSMA/CD (Carrier Sense Multiple Access, with Collision Detect) An Ethernet station that is ready to transmit listens for a clear channel (Carrier Sense). When the channel is clear, the station begins to transmit by asserting a carrier and encoding the packet appropriately. The station concurrently listens to its own signal, to permit the station to detect if another station began to transmit at the same time---this is called collision detection. (The collision corrupts the signal in a way that can reliably be detected.) Upon detecting the collision, both stations will stop 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:

No device driver currently presently permits direct block-oriented recording on DVD-RAM nor DVD+RW media, nor other recordable or rewritable media.

Recording (writing) of CD and DVD optical media requires a recording or media mastering application or tool, and both commercial and non-commercial options are available. See Section 9.7 for related details on CDRECORD (both non-DVD and DVD versions are available, and at least one commercial version is available), and also see DVDwrite (commercial) or DVDRECORD (open source).

For information on the GKDRIVER (SYS$GKDRIVER) generic SCSI device driver and of the the IO$_DIAGNOSE $qio[w] interfaces (of SYS$DKDRIVER, SYS$DNDRIVER and SYS$DQDRIVER) that are utilized by most CD and DVD recording tools to send commands to SCSI, USB or ATAPI devices (most USB and ATA devices---or more correctly, most ATAPI devices---can use SCSI-like command packets), please see the SYS$EXAMPLES:GKTEST.C example, and see DECW$EXAMPLES:DECW$CDPLAYER.C example and please see the various associated sections of the OpenVMS I/O User's Reference Manual.

For information on creating bootable optical media on OpenVMS, please see Section 9.7.3.

14.30 Office-Friendly (Quieter) Integrity rx2620 series?

The part number for the so-called Office-Friendly or Office Environment Integrity rx2620 series is AD244A.

The AD244A option is incompatible with and eliminates the redundant cooling and power supply capabilities of, but greatly reduces the sound output from, the Integrity rx2620 rack-mount computer-room variant. (Server rack-mount configurations are rated for sound output in the range of 70dB, per the HP QuickSpecs. Suitable for the intended installation into a computer room of course, but likely rather loud for an office environment installation.)

If you wish to retrofit this option into an existing Integrity rx2620 series, you must also order the HA113A1 (#53E) installation service; the option reportedly can not be installed by an end-user. Also reportedly, the option can be factory-ordered on custom configurations. If configuring for or converting an existing rack-mount configuration for the office environment, also consider acquiring the available pedestal-mounting option for the series.

14.31 KVM switches for AlphaServer and Integrity Servers?

Various folks have reported success with the Raritan series KVM (and specifically APKME the), and with the HP-branded KVM switches.

If you choose a KVM for use with Alpha or Integrity servers, do ensure it provides either Unix compatibility, X Windows compatibility, or specifies the Alpha or Integrity system. (This all usually means that the switch supports keyboards that use the so-called scanset three key-down and key-up sequences---key-down and key-up are key to the way X Windows and thus DECwindows works.)

Also see the discussion in Section 14.18 for related information, and particularly for older pinouts---for those keyboard and mouse devices that pre-date the PS/2 DIN connections, the PC VGA/SVGA video connection, and such. Almost all VAX systems pre-date these pinouts, and peripherals intended for the older Alpha systems also pre-date these pinouts.

14.32 Changing processor (CPU) identification codes?

There are various common motherboards used in a series of VAX systems, and these have a selectable id value. The enclosure and options differ, but the system boards are---save for the setting of the response---the same within certain pairings.

Table 14-9 Shared/paired VAX Boards
MicroVAX 3100 series VAX 4000 series Part Number
Model 90/KA50 Model 100/KA52 54-21797-01
Model 95/KA51 Model 105/KA53 54-21797-02
Model 96/KA54 Model 106/KA56 54-21797-03
Model 98/KA57 Model 108/KA59 54-24695-01

To change the system identification within the pairings, use a console command specifying the target CPU identification. For instance, the following command will set a 54-21797-01 series processor module to the KA50 response:

   >>> T 9D 50 
   confirm (y/n)? y 

These commands solely alter the identification returned within the specified pairings. These commands do not alter the system performance, and the commands can not and do not allow, for instance, a 54-21797-01 motherboard to become a 54-24695-01 motherboard.

See Section 14.14 for a more complete list of KA-series codes for various VAX processors.

Chapter 15
Information on Networks and Clusters

If you are searching for something here, please consider using the text-format FAQ.

The following sections contain information on OpenVMS Networking with IP and DECnet, and on clustering and volume shadowing, on Fibre Channel, and on related products and configurations.

15.1 How to connect OpenVMS to a Modem?

Please see the Ask The Wizard area topics starting with (81), (1839), (2177), (3605), etc.

For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW archive, please see Section 3.8. ATW has been superceded (for new questions) by the ITRC discussion forums; the area remains available for reference.

15.2 OpenVMS and IP Networking?

The following sections contain information on OpenVMS and IP networking, as well as IP printing topics.

15.2.1 How to connect OpenVMS to the Internet?

Some tutorial information and tips for connecting OpenVMS systems to the Internet are available at:

15.2.2 Connecting to an IP Printer?

To connect a printer via the IP telnet or lpr/lpd protocols, you will need to install and configure an IP stack on OpenVMS, and configure the appropriate print queue.

With current OpenVMS IP implementations, the choice of telnet or lpr/lpd really amounts to determining which of these works better with the particular printer involved.

To support network printing, the printer must include an internal or external NIC or JetDirect; an adapter connecting the network and the printer.

While it is normally possible to use a host-connected printer---when the host supports an LPD or telnet daemon, and OpenVMS and most other operating systems have the ability to serve locally-attached printers to other hosts on the network---it is generally far easier and far more effective to use a printer that is directly attached to the network. If your present printer does not have a NIC or a JetDirect, acquire an internal (if available) or external NIC or JetDirect. Or replace the printer. And obviously, most any operating system that can serve its local printers usually also provides a client that can access remote network-connected printers.

Please see the Ask The Wizard (ATW) area topics---starting with topic (1020)---for additional information on IP-based network printing.

For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW archive, please see Section 3.8. ATW has been superceded (for new questions) by the ITRC discussion forums; the area remains available for reference.

Please see Section 15.2.3 for information on Postscript printing.

15.2.3 How do I connect a PostScript printer via TCP/IP?

Using TCP/IP Services (UCX) as the TCP/IP stack, it is possible to configure queues using the UCX$TELNETSYM (TCP/IP Services prior to V5.0) or TCPIP$TELNETSYM (with V5.0 and later) in order to print to Postscript printers. This assumes however that the printer itself can convert whatever is passed to it into something intelligible. As an example, if the printer has an IP address of 123.456.789.101 and jobs should be passed to port 9100 then :

$ INITIALIZE/QUEUE/ON="123.456.789.101:9100" - 

$ INITIALIZE/QUEUE/ON="123.456.789.101:9100" - 

The port number of 9100 is typical of HP JetDirect cards but may be different for other manufacturers cards.

As a better alternative, DCPS Version 1.4 and later support IP queues using either HP TCP/IP Services for OpenVMS software or Process Software Multinet for OpenVMS. The usage of this type of interface is documented in the DCPS documentation or release notes, and the DCPS$STARTUP.TEMPLATE startup template file.

For general and additional (non-Postscript) IP printing information, please see topic (1020) and other topics referenced in that topic elsewhere within the Ask The Wizard area.

For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW archive, please see Section 3.8. ATW has been superceded (for new questions) by the ITRC discussion forums; the area remains available for reference. Also see:

Please see Section 15.2.2 for pointers to an introduction to IP printing.

15.2.4 How do I set a default IP route or gateway on OpenVMS?

If you have TCP/IP Services, then use the command for TCP/IP Services V5.0 and later:


And for earlier TCP/IP Services versions, use the command:

$ UCX 

15.2.5 How can I set up reverse telnet (like reverse LAT)?

Though it may seem obvious, Telnet and LAT are quite different---with differing capabilities and design goals.

Please see the documentation around the TCP/IP Services for OpenVMS TELNET command CREATE_SESSION. This command is the equivilent of the operations performed in LTLOAD.COM or LAT$SYSTARTUP.COM. There is no TELNET equivilent to the sys$qio[w] control interface for LTDRIVER (as documented in the I/O User's Reference Manual) available, though standard sys$qio[w] calls referencing the created TN device would likely operate as expected.

Previous Next Contents Index