Image Map Image Map
Results 1 to 7 of 7

Thread: Help Please: IBM 370 Mainframe System Operator Console

  1. #1
    Join Date
    Jun 2016
    Location
    British Columbia Canada
    Posts
    20

    Default Help Please: IBM 370 Mainframe System Operator Console

    I have been working on building a miniature sized replica of an IBM 370. I used a rendering of the front panel as a basis for the layout and installed MANY MANY small LEDs to act as the indicator lamps. Shift registers are being used to reduce the number of wires back to the CPU.

    During my mainframe programming days, I had very little access to the physical hardware (only computer operators had unlimited access to the hardware) and as a result there are a number of indicator lamps that seem important but I can't deduce their purpose. Nor can I find any reference material that would explain them.

    Does anyone out there know what the three red lamps under the section labelled "ECC" would do? I am tempted to assume that "ECC" means "Error Correcting Code" in reference to the ECC style of memory but at this time, high end computer typically had "EDAC" memory. Also the assumption that ECC is related to memory flies in the face of acknowledging IBMs habit of inventing new names for every technology they released.

    Usually it is safe to assume that red lamps imply a fault but the lamp entitled "BUSY" under the ECC heading seems like something that would illuminated whenever the ECC feature did its job (of correcting a fault).

    Any IBM 370 (model 145) experts out there that can help me with this? Thanks in advance if you can.

    Rob Carnegie
    Attached Images Attached Images

  2. #2
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    34,344
    Blog Entries
    18

    Default

    ECC = Error Correcting Code. (we called it SECDED at CDC; but we thought blinkenlights were old-fashioned).

    This should pretty much answer all your questions.

  3. #3
    Join Date
    Jun 2016
    Location
    British Columbia Canada
    Posts
    20

    Default

    Quote Originally Posted by Chuck(G) View Post
    ECC = Error Correcting Code. (we called it SECDED at CDC; but we thought blinkenlights were old-fashioned).

    This should pretty much answer all your questions.
    Yes, I remember thinking the same thing at the time. Most of the mainframes in the early part of my career had a HEXDEC keypad and segment digit display.

    I guess since it is a tribute, running on modern hardware, I will have to simulate an ECC failure once every hour or so for the sake of authenticity. Of the IBM systems I worked on where I had access to hardware, the reliability seemed so high that investing in a light bulb on the front panel seems unnecessary.

  4. #4
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    34,344
    Blog Entries
    18

    Default

    Memory parity/nothing/ECC was hit-or-miss on vintage mainframes. I remember reading pages and pages of bit errors that a given SECDED/Fire Code would correct, versus those that would be detected, versus errors that would go undetected.

    But go back to Seymour Cray and his CDC 6600. No memory parity anywhere--you test the hell of core and say "Parity is for farmers". That probably didn't sit well with government customers, so the 7600 had core parity; the Cyber 170, STAR and later machines used SECDED.

  5. #5
    Join Date
    Feb 2011
    Location
    NorthWest England (East Pondia)
    Posts
    2,412
    Blog Entries
    10

    Default

    Quote Originally Posted by robcarnegie View Post
    I have been working on building a miniature sized replica of an IBM 370. I used a rendering of the front panel as a basis for the layout and installed MANY MANY small LEDs to act as the indicator lamps. Shift registers are being used to reduce the number of wires back to the CPU.

    During my mainframe programming days, I had very little access to the physical hardware (only computer operators had unlimited access to the hardware) and as a result there are a number of indicator lamps that seem important but I can't deduce their purpose. Nor can I find any reference material that would explain them.

    Does anyone out there know what the three red lamps under the section labelled "ECC" would do? I am tempted to assume that "ECC" means "Error Correcting Code" in reference to the ECC style of memory but at this time, high end computer typically had "EDAC" memory. Also the assumption that ECC is related to memory flies in the face of acknowledging IBMs habit of inventing new names for every technology they released.

    Usually it is safe to assume that red lamps imply a fault but the lamp entitled "BUSY" under the ECC heading seems like something that would illuminated whenever the ECC feature did its job (of correcting a fault).

    Any IBM 370 (model 145) experts out there that can help me with this? Thanks in advance if you can.

    Rob Carnegie
    Pretty sure on our Honeywell L66 ( 1973/4 I think) it was called ECC although as you say it could detect multiple errors and correct single bit errors. The memory chips of the time were susceptible to errors from various sources including background radiation which produced soft errors. I think we used to get a few a day on the Honeywell and the Operating System kept a records of the corrections and produced a report which listed failing chips. There were also some diagnostics that could be used to test the memory. They could vary the voltage on the memory chips to weed out those at there margins which were then replaced by the Customer Engineer

    IBM had a similar reporting tool "EREP" but not sure if that recorded memory errors. I know when I started on IBM after 10 years of Honeywell (4381M3) the memory was much more reliable and EREP seldom showed any errors...

    https://en.wikipedia.org/wiki/Soft_error

    also try searching for

    "early memory chips radiation sensitivity"

    lots of interesting papers.
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  6. #6
    Join Date
    Feb 2015
    Location
    Campbell, CA
    Posts
    22

    Default

    When at HP I worked on the HP2700. It had some RAM boards that were using ECC memory. single bit correct, double bit detect. If while reading a location a single bit needed to be corrected, it would be written back in order to fix it. We had a low priority background process that would periodically read all the ram locations and scrub single bit errors out in order to avoid double bit noncorrectable errors. But I think now that the ECC was cost reduced out.

  7. #7
    Join Date
    Jun 2016
    Location
    British Columbia Canada
    Posts
    20

    Default

    I worked in a couple of sites that had Honeywell Level 6 systems. The larger of the two ran the MOD600 multi-user operating system which supported the customer’s choice of no error detection, parity detection or EDAC memory cards. We had parity boards in our system but I don’t remember there being anything on the control panel to report error. I think they were just reported into a log file.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •