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Conference noted::hackers_v1

Title:-={ H A C K E R S }=-
Notice:Write locked - see NOTED::HACKERS
Moderator:DIEHRD::MORRIS
Created:Thu Feb 20 1986
Last Modified:Mon Aug 03 1992
Last Successful Update:Fri Jun 06 1997
Number of topics:680
Total number of notes:5456

206.0. "What does >>>B/20000 do?" by SUBSYS::LAWLER () Thu Feb 20 1986 17:47

  I also asked this question in the Microvax notes file, but
  figured it would be interesting here also.  What does the
  /20000 do in the command >>>B/20000 mua0 when booting a 
  microvax II?  My vms internals book describes the function
  of bits 0-14 and 28-32 in R5 during boot, but skips the
  middle ones.  Am I missing something obvious?
  
                           al
T.RTitleUserPersonal
Name		DateLines
206.1"treat memory as the boot device"FROST::PIPERbill piperThu Feb 20 1986 20:149
It's something like "Use the pseudo-disk instead of the boot device".
After that, all swapping and such is done in memory, where the pseudo
disk lives.  I think this flag was invented when we figured that a
MicroVAX could have only the TK50 as a load device.

I expect to see Jay Olson answer this in the MicroVAX conference one
of these days.

-piper
206.2I want that psuedo disk driver.RICARD::HEINHein van den Heuvel, Valbonne.Fri Feb 21 1986 07:0012
    Hmmm,... Pseudo disks... Often I recieved requests for that. Almost
    as often I could advice alternative sollutions, but not always.
    I never had enough need to write the pseudo(?)-disk driver but if
    such an animal exists then I would like to play with it. Where can
    I find it? on the source kit? Could the psuedo disk facility mentioned
    by bill be used in a normal vms system?
    Eg; Assuming price is not important but performance is. Given a
    system with a 10Mb RDB database, could I copy it into memory, use
    it there (keeping the journalling on a real disk) with 'the speed
    of light' and copy it back to a real disk every now and then?
    
    Hein.
206.3ULTRA::PRIBORSKYTony PriborskyFri Feb 21 1986 12:286
206.4Other Ideas?RICARD::HEINHein van den Heuvel, Valbonne.Fri Feb 21 1986 12:596
    Re .3: Yes, that does not seem an optimal implementation for
    the suggested use. It could be a good starting point though!
    Any other ideas? Should we start a base note on this topic?
    Does anyone remember where he/she has seen this discussion before?
    
    Hein.
206.5BULOVA::VWS discussed PDDRIVERFROST::PIPERbill piperFri Feb 21 1986 14:306
re: .4

This was discussed in the VAXstation notesfile (now conference).  That's
BULOVA::VWS (hit KP7).  Don't remember the number.

-piper
206.6Another referenceAURORA::HALLYBTue Feb 25 1986 14:316
    It's also discussed in the VMS Performance database, AURORA's VTX
    server.  As it turns out, using PDs is a big win for one- and two-block
    reads.  The tradeoff is more CPU for more speed.  There are places
    where this can be worth doing, but it's not a panacea.
    
      John