John P. Baker wrote:
the functions performed by the Diagnose instruction are not published, but may impact any and all aspects of system operation, and if invoked by a user application built without access to that unpublished documentation, may negatively impact the proper functioning of the machine, requiring a Power On Reset and/or the assistance of a Hardware Support Engineer to bring the system back into proper working order.
On the 360/40, I used diagnose for two functions - one was to rewind all tapes, open the windows, and power them down; the other to read the panel switches (allowed me to use 7094 ForTran programs that read the sense switches). When we upgraded to a 360/50, the tape function was gone, and reading the sense switches caused a machine check unless all I/O was quiesced and no interrupts occurred. But luckily it didn't take a CE to restore the machine. With later models it got increasingly complex to do things correctly, and to find out what the available actions were.
Gerhard Postpischil Bradford, VT ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
