The DOS cdrom &c
Here is something interesting if you are playing with old DOS versions in emulators etc.
The DOS boot sector is designed to load DOS at 0000:7000, which corresponds to an address 07000x, just below the memory buffers. DOS then fiddles the low buffer eg to go to 6000 means go to 06000.
CD-ROMS etc load the boot sector at the same address 070000x, but give the address as 0700:0000. This means that the boot sector can't find the rest of the operating system as it loads.
The offset is that if you use a different boot sector, such as the one prepared by the freedos SYS command, you can use very old DOS versions on cdroms and diskettes.
The DOS boot sector is designed to load DOS at 0000:7000, which corresponds to an address 07000x, just below the memory buffers. DOS then fiddles the low buffer eg to go to 6000 means go to 06000.
CD-ROMS etc load the boot sector at the same address 070000x, but give the address as 0700:0000. This means that the boot sector can't find the rest of the operating system as it loads.
The offset is that if you use a different boot sector, such as the one prepared by the freedos SYS command, you can use very old DOS versions on cdroms and diskettes.
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