On 8/7/2011 8:48 PM, Robert A. Rosenberg wrote:
Thanks to the Wikipedia S/360 article I was able to download a copy of the S/360 PoPs manual can confirm my impression that ALL the S/360 opcodes were one byte long (and that B2 opcodes were not part of the architecture). In Fact - No opcode from A0-D0 was valid.
If you are confining yourself to normally used instructions, then you are correct. Depending on your interpretation, the opcode for Diagnose was three or four bytes, and just about every 360 model used different values. On the 360/40 I used one to read the panel switches, and another that causes all tape drives to rewind, unload, and power off. Similar ones I tried on the 360/50 gave me a machine check unless I/O was quiesced beforehand.
And I seem to recall that A0 was the opcode for loading emulator instructions on the 360/165.
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
