winscape 2225

I didn't think I was talking about memory protection at all. emoticon scrolls back then returns

Oh, I see where you thought I was talking about protection. Let me describe what I thinking about when I wrote that. The monitor says to Joe Device, go to track 3, sector 20, and move 50 words from there to here, physical memory address 1000. Oh, and when you're done, flag an interrupt and don't do any more.

When the monitor gets sees that the device has raised its hand and wants attention, it goes over to the address 1000, sniff around and decides that the data transfer was Ok. Then hands the address, 1000, to the user who asked for the 50 words of data and has been twiddling his thumbs getting twitchy, waiting for the data. Now the user has his 50 words of data, knows that he can start looking at it at loc 1000 and that loc 1049 will be the last bits of the data.

That is memory management. Memory protection ensures that the user cannot retrieve word 1050 without being punished or warned. Now, this memory protection can be done by software or it can be done by hardware or it can be by both hard and software. Memory protection can also give a user the option of locking in place without any interference from other users, programs, hardware, software, or the monitor...even field service ;-) and never getting relocated to another section of memory. I don't think that this kind of computing is done much anymore using the main CPU of a system.

That is keeping address spaces separate and in core all the time and is called bookkeeping. TOPS-10 did this by maintaining the User Page Map Page (UPMP). This page was a list of page addresses that "belonged" to the user. Each user (or process) had one, including the monitor. The monitor's was called the Exec Page Map Page. The way JMF put a page of data into a user's address space was by adding the page number into the table which I think was double-linked list.

Something tells me I've got this all f***ed up. I'm telling you guys that that other thing is not the first to go. Confidence in memory recall goes first.

I am not going to budge out on the roads today; it's Black Friday :-). For you non-USAians, Black Friday is now my name of the day after Thanksgiving when women seem to go berserk and indulge in insane shopping sprees. This has reminded me of lemming myth.

BAH