Multi CPU interlock question

A 4 byte address field in virtual storage has one updater and many readers If using load and store instuctions, will the readers always see a complete (valid) address, or could a CPU see a partially updated field while a store is in progress on another CPU? Is the answer any different for other

Re: Multi CPU interlock question

Hi Everyone, thanks for the answers. I did read the POP, but obviously not hard enough. (It is never an easy read). The block concurrency section explains it perfectly. The fullword is aligned so all should be good. The question about MVC was just out of interest. Thanks. Joe

Re: Multi CPU interlock question

Yes, your illustration is exactly what I was concerned about. My instinct was CS was just about updaters of storage, and not readers, so there must be some other type of protection for readers. Thanks, Joe

Re: Assembler III at Latham, NY 12110, USA

If you can assemble IKEA furniture, you can assemble anything.

Re: Probably dumb assembler question

I would restructure to open/close the DCB once Here using -ve value to indicate open has failed, or could use flags to track DCB status * Message is in WORKMSG on arrival here LTR4,MYDCB@ Get DCB address BM WRITTEN Previous open failed, skip

Re: Best way to multiply doublewords?

Thanks for the replies, much appreciated. We do have current processors, just my knowledge that is out of date :) The factor might not be a whole number, which is why I thought of FP, but I can see I can follow the multiply by a 64 bit divide by 100 to get a percentage. I take it the 'G' instruct

Subtasking program

After such a great response to my last post, I thought I would try here again for some useful advice on the best design for a program I am about to write. I have a mainline program that reads an input file and will then pass a record to a subtask to process. The subtask has a work cycle MQPUT messs

Re: Subtasking program

Thanks to everyone for the response to this, your insight will definately save me time, and I'll end up with something better than I would have on my own. I read up on the PLO instruction and got a headache, same type I get when I read how DAT translation works :) I will probably stick with CDS or

Re: Subtasking program

Re the ECB posting, I still don't get it..sorry. The agreement seems to be the the subtasks clears the ECB with a blocked instruction as soon as it comes out of the wait. Well actually after he has checked the post code, but there is no guarantee he will be dispatched before the poster. Consider Th

Re: Subtasking program

Quote "There are three queues - a requestor que, a process que and a reuseable element que. assuming que elements have the first word of which is the ptr to the next que element, the requestors push elements to the top of the requestor que with a single CS. The elements are therefore in reverse

Re: Subtasking program

"Please stay in touch and let us know how you are proceeding." I completed the program. I can now drive a flash copy of our IMS system using the messages extracted from the production IMS log, and requeued via MQ/OTMA, also checking the output messages produce matche what is expected. This means

Re: ASM Program to copy a file

This is a great thread. It is great to see someone enthusiastic about learning assembler. Your EODAD routine looks like a potential problem. The access method calls your EODAD inside the get. Here you would normally set a flag to say EOD occured and return to operating system (BR14), and test this