John, To me, the only valid count of instructions is that which one arrives at be recognizing distinct binary operations codes.
Using that rational, SIO/SIOF were distinct instructions (9C00, 9C01), whereas PC/PCF must be counted as one (1) instruction (B218). You have correctly pointed out that multiple instructions may be implemented by a single microcode/millicode routine. That is really not relevant to the "number of instructions", since that is hidden from the programmer. As far as we are concerned, every instruction could well be hardwired. John P. Baker -----Original Message----- From: IBM Mainframe Assembler List [mailto:[email protected]] On Behalf Of john gilmore Sent: Tuesday, August 31, 2010 12:33 PM To: [email protected] Subject: Re: number of new instructions The game of trying to count distinct instructions is, I suppose, innocuous; but doing so serves no good purpose. The PROP treats MVI, MVIY, and MVC as variants of a generic MOVE instruction; but it treats MVCLIN and MVCL as distinct instructions. There is, I believe, a hardware, instruction-implementation rationale for this distinction, but there is no functional one. Or again, as Tony Harminc has just pointed out, the mnemonic pair SIO, SIOF may be counted as one instruction or two. Examples of this sort can be multiplied ad nauseam by paging through the PROP. A count of distinct instruction mnemonics at time t--They are in an HLASM table having defined content at time t--can be precise. A count of instructions cannot. Qualitatively, it can be said that there are many more instructions than there once were; and that is enough. John Gilmore Ashland, MA 01721-1817 USA
