Most impressive VAX installations - VMS

This is a discussion on Most impressive VAX installations - VMS ; Glen Herrmannsfeldt wrote: > John Reagan wrote: > (I wrote) > >>> As I understand it, F, D, and G on Alpha also involve conversion to S/T, >>> but the conversion is done in hardware. The load/store instructions >>> load ...

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Thread: Most impressive VAX installations

  1. Re: Most impressive VAX installations

    Glen Herrmannsfeldt wrote:
    > John Reagan wrote:
    > (I wrote)
    >
    >>> As I understand it, F, D, and G on Alpha also involve conversion to S/T,
    >>> but the conversion is done in hardware. The load/store instructions
    >>> load
    >>> F, D , or G from memory into S or T form in registers, and do the
    >>> reverse
    >>> on store instructions.

    >
    >> As Tim and Bob have already mentioned, the register format isn't any
    >> of the memory formats of F/D/G/S/T. The load/store instructions know
    >> how to swap bits around. The various instruction formats essentially
    >> control rounding, precision, etc. So I suppose you can say that
    >> Alpha only knows one floating format since all the operate
    >> instructions only work on registers. The register format is
    >> essentially T format.

    >
    > Tim and Bob don't seem to mention that the byte order
    > is completely different. It seems strange to call them 'similar'
    > or 'implemented' given the differences.
    >


    Below is cut-n-paste from my post:

    F/G and S/T both look the same in registers and are very
    similar in memory format also. Field sizes are all the same,
    it's just a question of order. All are supported natively.

    ------------------------^^^^^

    I suppose I could have been clearer. You are correct. They are
    in different byte order in memory. However, in registers they
    are exactly the same.

    On the Alpha this is handled by the LD[G|F] instruction. On I64
    the AEST translator loads/stores F/G/D float with the use of of
    the mux2 instruction (followed or preceeded with a setf/getf) to
    achieve the same result.

    Tim.

  2. Re: Most impressive VAX installations

    Michael Moroney wrote:
    > Not a single system, but I came across comments in the disk shadowing code
    > for a bugfix where a byte field was being treated as a negative number
    > if it exceeded 127. That byte field was the number of nodes in a cluster,
    > and it was found by a customer (I think I know who), not internal testing.
    >
    > Also the test followed a decrement of that field, meaning a node left

    the
    > cluster, so the bug wouldn't have been seen unless there were 129 or
    > more nodes in the cluster at some point. (Supported limit was/is 96)


    SYSMAN once had a hard-coded limit of 128 nodes, but that limit was
    fixed in 5.5-1.

    $MOUNT/CLUSTER once had a hard-coded limit of 96 nodes, but that was
    fixed in 5.5-2.

    I worked with a customer who built a cluster which peaked at 151 nodes
    (150 VAXes plus 1 Alpha). See
    http://www.geocities.com/keithparris...avc_article.ps

    I've heard rumors of even larger clusters than that.

  3. Re: Most impressive VAX installations

    There also was a problem in V6.2-1H3 when the mount count field (UCB
    $B_ONLCNT) exceeded 127. This caused a MSCPSERV crash. You had to have
    more than 127. nodes in the cluster all mount the same disk. Been
    there, seen that ;-)

    Volker.

  4. Re: Most impressive VAX installations

    Bob Koehler wrote:
    > Just before we bought our first 11/780 running VMS 1.x, I spent
    > time on a Xerox Sigma 7 with a 3 foot diameter vertically mounted
    > disk.


    Ah yes, the RAD (Rapid Access Disk). Had fixed heads, with one head per
    track (we don't need no stinkin' seek time), and up to 512 tracks, thus
    512 heads. Made for fast swaps, which you needed to do a lot of in those
    days.

    Pictures at http://asuwlink.uwyo.edu/~jimkirk/rad.html

  5. Re: Most impressive VAX installations

    Richard B. Gilbert wrote:
    > Bob Eager wrote:


    >
    > There was a shop on RT 130 just south of Hightstown, NJ where I saw a
    > disk platter that must have been three to four FEET in diameter! Ancient
    > technology of course.


    IBM Ramac ?. There was one of those in a scrap yard in Newbury (Uk) in
    the 1960's, the result of a USAF base closing at Greenham Common. The
    drive had the disks vertically on a spindle, with 2 axis head movement -
    vertically to select the platter, then laterally to select the track .
    Probably 10 or 15 platters around 3 feet across iirc. overall height
    around 6 feet.

    I was late teens at the time and spent hours removing parts and some of
    plug in modules, one module per flip flop or gates etc. Carefully
    removed all the r/w heads from a fixed head drum drive as well, which I
    guess would have been used for cache. This was a valve (tube) computer
    and probably still have some of the heads and stuff like wire ended neon
    lamps that were everywhere in the plugin modules. The majority of the
    tubes were 6211 double triodes, a mil spec version of the 12AU7 or similar.

    Knowing what I know now, I should have bought the whole thing, though it
    would probably have filled the ground floor of a house. They probably
    dumped a couple of hundred tons of aviation, electronics, radio and test
    gear scrap, much with a hammer through the face to stop it being reused.
    As young radio & electronics enthusiast, it was like being transported
    to paradise :-)...

    Chris

  6. Re: Most impressive VAX installations

    On 9 Nov, 15:07, ChrisQ wrote:
    > Richard B. Gilbert wrote:
    > > Bob Eager wrote:

    >
    > > There was a shop on RT 130 just south of Hightstown, NJ where I saw a
    > > disk platter that must have been three to four FEET in diameter! Ancient
    > > technology of course.

    >
    > IBM Ramac ?. There was one of those in a scrap yard in Newbury (Uk) in
    > the 1960's, the result of a USAF base closing at Greenham Common. The
    > drive had the disks vertically on a spindle, with 2 axis head movement -
    > vertically to select the platter, then laterally to select the track .
    > Probably 10 or 15 platters around 3 feet across iirc. overall height
    > around 6 feet.
    >
    > I was late teens at the time and spent hours removing parts and some of
    > * plug in modules, one module per flip flop or gates etc. Carefully
    > removed all the r/w heads from a fixed head drum drive as well, which I
    > guess would have been used for cache. This was a valve (tube) computer
    > and probably still have some of the heads and stuff like wire ended neon
    > lamps that were everywhere in the plugin modules. The majority of the
    > tubes were 6211 double triodes, a mil spec version of the 12AU7 or similar.
    >
    > Knowing what I know now, I should have bought the whole thing, though it
    > would probably have filled the ground floor of a house. They probably
    > dumped a couple of hundred tons of aviation, electronics, radio and test
    > gear scrap, much with a hammer through the face to stop it being reused.
    > As young radio & electronics enthusiast, it was like being transported
    > to paradise :-)...
    >
    > Chris


    You sure it wasn't just new technology replacing old at Greenham
    Common? I remember the peace campaigners outside there on the TV in
    the 1980s...

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