VAX-VMS Storage Notes:

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Lots of confusion can creep in when something simple evolves into something complex. Confusion is exactly what happened when my department recently (1998.02.xx) attempted to migrate RFxx series drives from a uVAX-4300 to a recently acquired (but used) VAX-6420. This problem was made worse we when discovered that the SHOW DSSI console command on our particular VAX-6420 was not implemented and console upgrade kits for the 6420 were no longer available. In retrospect, I think that some confusion came from the fact that the VAX-6420 was probably designed for use with an HSC based storage system. I hope that some of this information may be of use to someone else since there seems to be a lot of used VAX systems still available at very reasonable prices. Besides, who really wants to migrate to a UNIX box when a VAX-VMS system will do a better job?

Basic Glossary:

Name Description
  • Backplane Interconnect - is a computer system backplane for medium to large size VAX processors.
  • This technology made UNIBUS virtually obsolete in the VAX world.
  • 13.3 Megabytes/second maximum transfer rate. (Megabytes, not Megabits)
  • Features ZIF (zero insertion force) backplane sockets.
  • Computer Interconnect
  • 80 Megabytes/second depending on the adapter
  • Digital Storage System Interconnect
  • 1.5<5.0 Megabytes/second depending on the adapter
  • Hierarchical Storage Controller
  • a special purpose computer that off loads storage management from the host computers
  • Integrated Storage Element
  • a DSSI device that contains an HSC like embedded intelligent controller and an on board MSCP server.
  • A Q-Bus based MSCP disk controller
  • A "BI" based MSCP disk controller
  • Mass Storage Control Protocol
  • A small computer system backplane for PDP and early VAX processors.
  • Similar in concept to the Unibus except Q-bus address and data lines are multiplexed onto the same wires in order to reduce costs
  • System Communication Services
  • Small Computer Systems Interconnect (pronounced scuzzy)
  • StorageWorks Building Block
  • A "56 line" computer system backplane for PDP and VAX processors.
  • Address and data lines are NOT multiplexed together as is the case with Q-Bus
  • A Micro VAX is usually a small to medium sized machine that is based on Q-Bus
  • Virtual Address eXtension (refers to Digital's 32 bit processor technology)
  • all early 700 series machines could run PDP-11 code in compatibility mode (this was done to allow customers to migrate from PDP to VAX without rewriting their software
    • VAX-11/780 (the architecture reference platform. "One VUP" still means "one VAX-11/780")
    • VAX-11/750
    • VAX-11/730
  • See BI
  • See XMI
  • Virtual Memory System
  • refers to Digital's VAX operating system software
  • eXtended Memory Interconnect
  • a 64 bit wide computer system backplane for medium and large VAX processors
  • supported 40 bits of address space (1 Terabyte)
    • only 30 bits on VAX-6000 series 200 to 500
    • only 32 bits on VAX-6000 series 600 and higher
  • 100 Megabytes/second maximum transfer rate. (Megabytes, not Megabits)
  • Features ZIF (zero insertion force) backplane sockets.

Example Configurations

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Neil Rieck
Kitchener - Waterloo - Cambridge, Ontario, Canada.