Hi, > I always wanted to know this, couldn't find it on google. > Is it possible to switch from long mode back to let's say real mode?
Probably yes, but very slow. Until people are able to have more than 64 GB RAM in their PC, using PAE is a lot faster and easier even though it is not "the technology of the future". >> which apps would use it and for what? > The ram dumper! Or maybe a ram tester? Ramdumper makes sense, maybe even switching to/from long mode every few MB would be bearable there. Ramtesters do already work best without OS, see memtest86+ and memtest86. > Future applications? :D Which? > Don't we have more phantasm? Otherwise poor performance. :p Do you know any DOS app which is RAM bound and forces you to have more than, say, 500 MB RAM? Are you sure you should not write a multi core CPU DOS extender first? ;-) > Don't you think it's theoretically possible to modify an > existing DOS extender to > - save the state > - switch to long mode > - do something While DOS and BIOS are frozen, IRQ cannot be handled. > - return to state > - do something in v86 You probably have to switch all down to real mode and it adds complexity to resurrect the v86 of your EMM386 or "normal DOS extender mode" from that point again. > - loop > while staying compatible with all that stuff? Possible, yes. Useful, probably no. > For example DOS_extender in wikipedia. > > It says it switches all time from v86 OR realmode > (means not limited to v86) to protected mode and back. Because v86 TASKS and protected mode TASKS can exist simultaneously in a 32 bit multitasking environment. The DOS extender does exactly that. > Why a switch to long mode shouldn't work? Because v86 cannot coexist with long mode. You cannot simply switch tasks, you have to switch the mode of the whole CPU, much much slower and much more complex. Even more complex than the annoying way 286 extenders had to follow to "reboot" the CPU into real mode when they had to leave protected mode, I would say. > Well, for a forensic tool (a ram dumper) a full blown 64 bit > os is like "operating success, patient dead". Not much sense. That is true. Otoh, how do you avoid your BIOS destroying RAM contents already while you boot the forensic tool? The to-be-analyzed software could put the to-be-hidden data into the first 1 MB deliberately, as that is very often checked and wiped at boot to ensure stable boot. >>> There are some but dd as command line tool is nicer in some cases. > Mostly graphical tools and on their homepages I don't > find the term "raw image" or something similar, mostly > proprietary formats. How about Linux ghost clones, g4l or so? I also meant that Heise had a DOS tool for disk imaging which was almost certainly text mode or at most DEFRAG style text mode GUI as far as I can remember... Eric ------------------------------------------------------------------------------ Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
