HP 21MX/F and OS choices (was Lookee what I just got!)

What they have in common is what matters. Why would any program that runs in 32K, less the BBL area (64 words) not run correctly under the SYSTEM map with 21MX memory protection disabled? When HP-IPL/OS runs something like HP BASIC, it loads the program to be run into a 32K word virtual address space(called a page in IPL). It them pokes in a modified sort of BBL program. A single function can remap the SYSTEM and USER maps, and make that virtual address space the SYSTEM map and transfer control to any address in that page. The program that ~had~ been loaded into VM is now running on its very own 32K word machine, IRQ vectors, DCPC transfers, everything. When that program (HP BASIC in this case) jumps to the special BBL loader a tiny DMS program unswaps the DMS maps and jumps to a special entry point in IPL, the threaded interpreter keeps chugging along as if it also is being run on a totally different CPU. Early versions of RTE could be run in VM pages, in fact, and program that does not take control of the DMS mapping registers must, be definition, run normally under these conditions. The system map is the system map, no matter where in physical memory it is mapped to. At power on, its the first 32K words of physical address space. So what if it happens to be mapped to some other physical address space? There is no way for a non-DMS program to ever know this is the case. Why would it not run perfectly? ----- Original Message ----- From: "Jay West" <jwest at classiccmp.org> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Sent: Thursday, January 11, 2007 12:14 AM Subject: Re: HP 21MX/F and OS choices (was Lookee what I just got!)