HP OpenVMS Systems Documentation
The OpenVMS Frequently Asked Questions (FAQ)
14.10 What is the layout of the VAX floating point format?
The VAX floating point format is derived from one of the PDP-11 FP formats, which helps explain its strange layout. There are four formats defined: F 32-bit single-precision, D and G 64-bit double-precision and H 128-bit quadruple precision. For all formats, the lowest addressed 16-bit "word" contains the sign and exponent (and for other than H, some of the most significant fraction bits). Each successive higher-addressed word contains the next 16 lesser-significant fraction bits. Bit 15 of the first word is the sign, 1 for negative, 0 for positive. Zero is represented by a biased exponent value of zero and a sign of zero; the fraction bits are ignored (but on Alpha, non-zero fraction bits in a zero value cause an error.) A value with biased exponent zero and sign bit 1 is a "reserved operand" - touching it causes an error - fraction bits are ignored. There are no minus zero, infinity, denormalized or NaN values.
For all formats, the fraction is normalized and the radix point assumed to be to the left of the MSB, hence the following range: 0.5 less than or equal to f and less than 1.0. The MSB, always being 1, is not stored. The binary exponent is stored with a bias varying with type in bits 14:n of the lowest-addressed word.
The layout for D is identical to that for F except for 32 additional fraction bits.
Example: +1.5 in F float is hex 000040C0 (fraction of .11[base 2],
biased exponent of 129)
14.12 Where can I find information on NetBSD for VAX systems?
Gunnar Helliesen maintains a NetBSD VAX FAQ at
14.13 What system disk size limit on the MicroVAX and VAXstation 3100?
System disks larger than 1.073 gigabytes (GB)---1fffff hexidecimal blocks -- are not supported on any member of the VAXstation 3100 series and on certain older members of the MicroVAX 3100 series, and are not reliable on these affected systems. (See below to identify the affected systems---the more recent members of the MicroVAX 3100 series systems are NOT affected.)
Various of the SCSI commands used by the boot drivers imbedded in the console PROM on all members of the VAXstation 3100 series use "Group 0" commands, which allow a 21 bit block number field, which allows access to the first 1fffff hexidecimal blocks of a disk. Any disk references past 1fffff will wrap---this wrapping behaviour can be of particular interest when writing a system crashdump file, as this can potentially lead to system disk corruptions should any part of the crashdump file be located beyond 1.073 GB.
More recent systems and console PROMs use "Group 1" SCSI commands, which allow a 32 bit block number field.
There was a similar limitation among the oldest of the MicroVAX 3100 series, but a console boot PROM was phased into production and was made available for field retrofits---this PROM upgrade allows the use of the "Group 1" SCSI commands, and thus larger system disks. There was no similar PROM upgrade for the VAXstation 3100 series.
Systems that are affected by this limit:
14.15 Where can I get software and hardware support information?
Please contact the HP Customer Support Center. Services and information, manuals, guides, downloads, and various other information is available via the support link at:
Various hardware and system documentation is available at:
TSM (Terminal Server Manager), DEChub, DECserver, etc. information:
14.16 Where can I get hardware self-maintenance support assistance?
The HP Parts Directory and the HP Parts Reference Guide (arguably the most direct descendents of the HP Assisted Services program, of the Compaq Assisted Services program, and of the now-ancient DECmailer program) are available to customers that wish to maintain their own system(s) (self-maintenance), but that wish some level of assistance in acquiring specific parts, hardware diagnostics and hardware manuals for the system(s), and that wish to have access to spares and module-level repairs for customer-performed hardware module swaps:
The HP Parts Reference Guide replaces the CAS-Catalog and DAS-Catalog parts catalogs and related resources.
Details of the available self-maintenance programs and services can
vary by geography and by the particular services channel(s), and
current program specifics are available via the above URLs.
Various VAX and Alpha consoles are designed to process the BREAK signal, treating it as a HALT request.
A BREAK is a deliberately-generated serial line framing error.
When a serial line device such as a terminal powers up (or sometimes when powering down) it can generate framing errors. These framing errors are indistingushable from a BREAK signal.
When a BREAK is received on a serial line console for various VAX systems---including most VAXstation, MicroVAX, and VAX 4000 series---it is typically interpreted as a HALT. Alpha systems will also often process a BREAK in a similar fashion, halting the system.
There is no uniform or generally-available way to disable this behaviour on every VAX or Alpha system. On some systems, BREAK processing can be disabled in favor of [CTRL/P], or [CTRL/P] is the only way to halt the processor.
The most common way to avoid these halts is to disable the serial line console or to simply not power-cycle the console terminal. There is certain important system state information that is displayed only on the console, OpenVMS expects to always have access to the system console.
Older HP keyboards (those with the DIGITAL logo and the RJ modular jacks), older HP mice (those with the DIGITAL logo and with the RJ modular jacks, or with a DIN connector with pins in a configuration other than the PC-standard DIN connector pin orientation), and older video monitors (with RGB synch-on-green video signaling) all use signaling formats and/or communications protocols that differ from the PC standards, and are not (easily) interchangable nor (easily) compatible with typical PC peripheral device controllers. The LK201 and LK401 keyboards, the VSXXX series mice, the VR260 and VR290 monitors, etc., are incompatible with most PC systems and with most KVM switches.
Newer HP (and Compaq) keyboards (those with with PC-style DIN plugs, and the HP, Compaq or DIGITAL logo), newer HP mice (with PC-pin DIN plugs, and the HP, Compaq or DIGITAL logo), and newer video monitors (multi-synch) are often interchangeable with "industry standard" PC systems, and can often be used with most PC peripheral device controllers. LK461, LK463, LK46W, LK471, PC7XS-CA, VRC16, VRC21, TFT-series LCD flat-panel displays, etc., are typically reasonably compatible with most PC systems, and will usually perform as expected within the limits of the hardware. (For details of CRT and LCD display compatibility, please see Section 14.19.)
Rule of thumb: if the peripheral device component was sold for use with the DEC 2000 (DECpc 150 AXP), an AlphaServer series, an AlphaStation series, or a more recent Alpha system, it will probably work with a PC peripheral controller or with a PC-compatible KVM switch. If the peripheral device component was sold for use with an VT420 or older terminal, most VAX, most VAXstation, and most Alpha systems with names in the format DEC [four-digit-number], it probably won't work on a PC system or with a PC-compatible KVM.
Note that the above is a general guideline, and should not be read to indicate that any particular peripheral device will or will not work in any particular configuration, save for those specific configurations the device is explicitly supported in.
Software Integrators sells a video adapter card called Gemini P1 which will drive many of the older HP (DIGITAL-logo) fixed-frequency monitors on a PC system:
The DIGITAL (classic 2-5-2-style) part number 29-32549-01 converts the output from the RGB cable (3 BNC, synch-on-green) that comes with the VAXstation 3100 and VAXstation 4000 series to a female SVGA D connector. You may be able to find third-party converters or adapters (3 BNCs with synch-on-green signaling to 5 BNCs with VGA/SVGA, or to 15-pin VGA/SVGA.
This adapter will allow PC multisync monitors with the needed frequency specifications to be used with the VAXstation series synch-on-green video connection. It may well also work with a VAXstation 2000 series systems, but specifics and performance of that combination are not immediately known at this writing.
The protocol definition for the old DIGITAL keyboard and mouse interfaces is buried at the back of the QDSS section in the old VAXstation II manual, specifically, in the back of the VCB02 Video Subsystem Technical Manual (EK-104AA-TM). The keyboard wiring and protocol is in appendix B, and occupies circa 44 pages. The mouse is in appendix C, circa 12 pages.
To determine the answer to the "will this video monitor or this LCD panel work with this graphics controller?" question, please first locate the resolution(s) and the frequencies that are possible/supported at both ends of the video cable (on the display and on the graphics controller, in other words), and then determine if there are any matching settings available. If there are multiple matches, you will need to determine which one is most appropriate for your needs.
You will also need to determine if the video monitor or graphics controller requires the 3 BNC signaling with the synchronization signals on the green wire, or the 5 BNC signaling common on many PCs, or other connections such as the DB15 video connector or USB connector used on various systems. (BNC signaling is comparatively old, but prevalent with many older hobbyist AlphaStation or VAXstation configurations.)
If there are no matches, you will likely need to change the hardware at one or both ends of the video cable.
The refresh frequencies for many devices have been posted to comp.os.vms and/or other newsgroups. Search the archives for details. Also see:
LCD-based and plasma-based flat-panel displays are generally compatible with all recent OpenVMS Alpha systems and supported graphics controllers. For best results, you should generally set the graphics controller to match the native LCD or plasma display resolution and (for LCD displays) also set the controller refresh rate to 60Hz. Check your graphics controller and your display documentation for any device-specific requirements and/or configuration recommendations.
Some of the older graphics controllers around do not necessarily generate stable signals at 60 Hz, if the controller can even generate that refresh rate; you may end up upgrading to a less-old controller. (At least some of the PowerStorm 3D30 and PowerStorm 4D20 series controllers, for instance, are not necessarily the best choice for 60 Hz operations with an LCD, based on empirical testing with an AlphaStation XP1000, PowerStorm 3D30, and a TFT2025 series LCD. Degraded or mismatched signals produce degraded displays, obviously. The newest graphics controllers compatible with your particular system are generally better choices here for use with LCD; the Radeon 7500 series is a good choice for most EV6-class AlphaStation systems, for instance.
14.21 Why does my LK401 keyboard unexpectedly autorepeat?
There are several modes of failure:
14.22 Problem - My LK411 sends the wrong keycodes or some keys are dead
Check the firmware revision on the keyboard. Hardware revision B01 introduced an incompatability with the device driver which causes the keyboard to not be recognized correctly. There is a patch available to fix this problem: [AXPDRIV06_061] - the fix is also included in OpenVMS V6.2. The rev A01 keyboard, and the LK450 should work without problems.
If you are working from another operating system platform, please see
the DECxterm tool and related information on OpenVMS Freeware V5.0.
Ensure you have a version of the Alpha SRM console with support for the DE500 series device. Apply ALL mandatory ECO kits for the OpenVMS version in use, and also apply the CLUSIO, ALPBOOT, and ALPLAN kits, and apply any available ALPCPU ECO kit for the platform.
To check the DE500 device hardware id from OpenVMS, use the following command:
The "hardware version" will be displayed.
To set the DE500 speed and duplex settings via the associated Alpha SRM console environment variable, see Table 14-4.
Fast Ethernet (100Base, 100 megabit) controllers such as the DE500 series have a pair of connections available---while traditional Ethernet (10Base, 10 megabit) is inherently a half-duplex protocol, Fast Ethernet can be configured to use one or both of the available connections, depending on the controller. Fast Ethernet can thus be half- or full-duplex depending on the configuration and the capabilities of the network controller and the Ethernet network plant. Some Fast Ethernet controllers can also operate at traditional Ethernet speeds, these controllers are thus often refered to as 10/100 Ethernet controllers.