shmuel+...@patriot.net (Shmuel Metz , Seymour J.) writes: > No! The channel should pass CCW opcodes[1] on to the controller and > let the controller handle them. > > [1] Other than TIC.
note that more recent zHPF for FICON with TCW ... batch up multiple channel commands for download. this is similar to the underlying fibre channel standard (originally from late 80s/early 90s) before FICON (inefficiency) was layered on top (from my perspective involved with fibre channel standard ... it appeared that the POK channel engineers that had gotten involved, were trying to revert to ESCON but using the faster fibre channel transfer rate). reference http://www-03.ibm.com/systems/z/hardware/connectivity/ficon_performance.html and ftp://ftp.software.ibm.com/common/ssi/sa/wh/n/zsw03059usen/ZSW03059USEN.PDF from above: zHPF improves upon FICON by providing a Transport Control Word (TCW) that facilitates the processing of an I/O request by the channel and the control unit. The TCW has a capability that enables multiple channel commands to be sent to the control unit as a single entity instead of being sent as separate commands as in FICON CCW. In addition, the channel is no longer expected to process and keep track of each individual CCW. Instead, the channel forwards a chain of commands to the control unit to execute. Reduction in this overhead cost increases the maximum I/O rate possible on the channel and improves the utilization of the various sub-components along the path traversed by the I/O request. ... snip ... original os/360 paradigm was channel programs were built by application (or libraries) and passed to the system with EXCP for execution. the mainframe channel program paradigm uses "real" addresses for execution. the original virtual machine cp67 in the 60s ... (for SIO simulation) had to scan virtual machine channel programs, making copy of the channel program, that replaced the virtual machine virtual addresses with "real" addresses. when initial VS2 was being built ... it started off with SVS (single virtual storage) ... effectively laying out an MVT in a 16mbyte virtual address space ... minimum changes hacked into the side of MVT to setup the virtual address space table, handle page fault, do paging operations. Possibly the biggest effort for initial mapping of OS/360 to virtual memory was hacking CP67's "CCWTRANS" into EXCP processing to handle scanning of the passed channel program (that had virtual addresses) to create a copy that had real addresses. EXCPVR call (aka virtual=real) was added to bypass scanning & creating copy ... that invoking application had done a bunch of special stuff to fix virtual pages in real storage and create channel programs with the real addresses ... rather than virtual addresses. reference to use of excpvr http://publib.boulder.ibm.com/infocenter/zos/v1r12/topic/com.ibm.zos.r12.idas300/efcprs.htm and http://publib.boulder.ibm.com/infocenter/zos/v1r12/topic/com.ibm.zos.r12.ieaa600/excpvrm.htm past posts mentioning EXCPVR http://www.garlic.com/~lynn/2007q.html#8 GETMAIN/FREEMAIN and virtual storage backing up http://www.garlic.com/~lynn/2007s.html#2 Real storage usage - a quick question http://www.garlic.com/~lynn/2008i.html#68 EXCP access methos http://www.garlic.com/~lynn/2011p.html#118 Start Interpretive Execution recent posts mentioning zHPF/TCW http://www.garlic.com/~lynn/2012m.html#3 Blades versus z was Re: Turn Off Another Light - Univ. of Tennessee http://www.garlic.com/~lynn/2012m.html#4 Blades versus z was Re: Turn Off Another Light - Univ. of Tennessee http://www.garlic.com/~lynn/2012m.html#5 Blades versus z was Re: Turn Off Another Light - Univ. of Tennessee http://www.garlic.com/~lynn/2012m.html#11 Blades versus z was Re: Turn Off Another Light - Univ. of Tennessee http://www.garlic.com/~lynn/2012m.html#13 Intel Confirms Decline of Server Giants HP, Dell, and IBM http://www.garlic.com/~lynn/2012m.html#28 I.B.M. Mainframe Evolves to Serve the Digital World http://www.garlic.com/~lynn/2012m.html#43 Blades versus z was Re: Turn Off Another Light - Univ. of Tennessee http://www.garlic.com/~lynn/2012n.html#9 How do you feel about the fact that today India has more IBM employees than any of the other countries in the world including the USA.? -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
