Hello TK and Paul, > FreeDOS (and other MS-DOS compatibles) will ask the BIOS --- via int > 0x12, or [0:0x413] --- how much memory is available, rather than always > assuming 640 KiB.
Yes. Which is still more simplistic that processing the full BIOS reported list of which areas are for what. Only the latter tells "there is something at 5800:0", which means DOS will not normally NOTICE this problem and just run into conflicts and crashes. UNLESS you manually (or by writing a suitable tool) reserve a 5800:0 block. > If 0x5800:0 is "unavailable" but the BIOS says it is "available", then > there is a problem somewhere, and it is not in FreeDOS. I can think of > some possibilities: It is normal that older types of queries return simplified descriptions of the state of the world, compared to newer types. So you could say it is the "fault" of DOS to not use the full BIOS list of areas. But as you already know, the int 12 or 40:13 method has worked fine for 40 years. > (1) the CMOS settings are out of whack; > (2) some RAM chips have gone bad; or None of those would have been likely to be REPORTED in a memory map. Of course if you can change CMOS settings in a way which makes your BIOS agree that it no longer needs the 5800:0 area reserved, great. But to be honest, it is unlikely that such a setting is provided. In any case, the settings are not "out of whack", they just fail to give DOS the amount of RAM below 640 kB that apps want. You could say it is a "bug" in BIOS DOS compatibility. > (3) the BIOS is buggy. Yes and no. The BIOS ignores the needs of DOS style operating systems by daring to reserve areas below the first > 600 kB of RAM and by only announcing that in a way which would have been used only by UMB, XMS, etc. drivers on DOS compatible PC. Luckily DOS can be made aware of the new impolite style of the BIOS on Paul's PC and my "scientific" interest is whether manually blocking the problematic 5800:0 area will make more DOS apps in FreeDOS 1.3rc4 work well. As Tom has already said, reserving areas so low in DOS space will get in the way of many DOS apps which want more consecutive RAM, so various apps may just fail to run, but at least there should be fewer crashes. Regards, Eric _______________________________________________ Freedos-devel mailing list Freedos-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-devel
