On Mon, Feb 27, 2017 at 11:59 PM, Angelo Papenhoff via cctalk < cctalk at classiccmp.org> wrote: AFAIK, there weren't any formal MIPS architecture standards published for the early versions of the architecture, though there may have been such things internally to MIPS. That was not an uncommon practice for computer architectures; for instance, the formal DEC VAX architecture standard was a DEC confidential document not available to customers, even though there was plenty of customer documentation covering most aspects of the architecture. It might be worth asking on comp.arch.

On Tue, 28 Feb 2017, Angelo Papenhoff via cctech wrote: A differently formatted copy of the same document used to be available at <http://techpubs.sgi.com/library/manuals/2000/007-2597-001/pdf/007-2597-001.pdf> though `techpubs.sgi.com' has been recently taken offline I'm told (and I haven't checked if `archive.org' has a copy). In either version of the document you can see how the ISA has progressed in the opcode tables towards the end of each appendix; this might be the best original ISA reference readily available. As to the earlier ISA levels I believe their definitions were only buried as parts of the respective MIPSCO processor manuals, i.e. the R2000/R3000, the R6000 and the R4000/R4400. The latter is available online in several places; originally at <http://www.mips.com/Documentation/R4400_Uman_book_Ed2.pdf> and <http://techpubs.sgi.com/library/manuals/2000/007-2489-001/pdf/007-2489-001.pdf>. The final version of the R6000 manual may not have been made. A very early revision was found and has been scanned and published at <ftp://ftp.linux-mips.org/pub/mips/docs/r6000/> as tarballs of TIFF images (I have made a PDF conversion and placed the result at <ftp://ftp.linux-mips.org/pub/linux/mips/people/macro/MIPS/>). It is inaccurate and lacks opcode encodings. I have seen a copy of the original R2000 manual once, in the form of a collection of pages in a ring binder. That copy may have been lost since. Silicon manufacturers like IDT, LSI Logic, Performance Semiconductor or Siemens published their R2000/R3000 (and R2010/R3010 FPA) implementation manuals though that may serve as a reference; you should be able to track down scanned copies online. HTH, Maciej