daasch@psueea.UUCP (Robert Daasch) (05/05/87)
As suggested I am reposting this to a broader set of newsgroups; ======== I would be interested in expanding the recent series on "on-chip or off-chip MMU" to coprocessors and the "ideal protocol?" Here at PSU we are working on a IC subsystem (MOSIS CMOS etc.) for supporting the 020 protocol. I think it is fair to say that it is based on a notion that a coprocessor is a special purpose peripheral that shares code (operands etc. are inline with the 020 instructions). I don't know details but I believe Intel doesn't use this scheme with the 386. Questions to get started could be: 1) How is the coprocessor limited (both hardware and software ) by the protocol? 2) Is there a reasonable sized "set of protocols" that would support a broad spectrum of coprocessors? 3) What coprocessors are going to be needed? This would get away from rehashing FPU, MMU and the like. Reply to ...!tektronix!psu-cs!psueea!daasch or post and I'll gladly collect an archive. Thanks, Rob D. ...!tektronix!psu-cs!psueea!daasch daasch@portland.csnet
dan@prairie.UUCP (05/07/87)
In article <413@psueea.UUCP> daasch@psueea.UUCP (Robert Daasch) writes: >I think it is fair to say that it is based on a notion that a coprocessor >is a special purpose peripheral that shares code. I don't know >details but I believe Intel doesn't use this scheme with the 386. It doesn't for the MMU (since that's on chip), but the whole 8086 series uses exactly that approach with the 80x87 arithmetic coprocessor and the 8089 (?) I/O coprocessor, and perhaps others. There are dedicated instructions for each coprocessor function, for which the co-p watches the bus. The main processor does address operand decoding and fetching, and the coprocessor steps in to actually receive or store operands at the appropriate time in instruction execution. There are only two lines that explicitly connect the processors, and they are used for timing. -- Dan Frank (w9nk) ARPA: dan@db.wisc.edu ATT: (608) 255-0002 (home) UUCP: ... uwvax!prairie!dan (608) 262-4196 (office) SNAILMAIL: 1802 Keyes Ave. Madison, WI 53711-2006