IBM Mainframe Discussion List <[email protected]> wrote on
07/19/2019 06:16:33 PM:
>
> Who remembers how to "ripple core" on a 360/75J? Back in the
> day, I was taught that it "wrote un-digit zeros" to all storage
> locations (main + LCS) on the box. If course, an IPL was required
> after this was done.
>
> Not sure how widely it was used. A simple yes or no is OK if
> you cannot provide details.
Bob, in the very early 80's, I was a computer operator at Time Sharing
Resources (TSR) in Great Neck, LI. We had two S360/75Js running APL in a
three-partition DOS environment. Prior to each IPL, we had to "clear
memory" using the console switches on the very impressive 360/75 light
panel/console.
The process was:
1. Load GR 0 with zeros.
2. Set the data keys with a multiple-store instruction (Op code 90,
R2 other than 0, all other positions zero).
3. Press the load A-B regs push button.
4. Turn on the enable storage ripple switch.
5. Press start.
Successive storage locations are stored with zeros. Storage wraps
around and keeps running until computer or system reset is pressed.
I'd like to say that I remembered all of this over the 37-years since I
IPLed a 360/75. That would not be true. The process is described in "Field
Engineering Manual of Instruction, 2075 Processing Unit - Volume 4" which
is on bitsavers.org (
http://www.bitsavers.org/pdf/ibm/360/fe/2075/223-2875-1_2075_Processing_Unit_Field_Engineering_Manual_Volume_4_Mar66.pdf
).
Five 360/75Js (running a modified version of OS/360 called RTOS)
constituted the Apollo Real Time Computing Complex. At the time that I
worked at TSR there was a rumor that the machines had been purchased from
NASA. I've never been able to confirm that rumor.
- Mark
Mark Nelson, CISSP®, CSSLP®
z/OS Security Server (RACF) Design and Development
IBM Corporation
2455 South Road MS/P388
Poughkeepsie, NY 12601
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