4 ms·
MSDOS did have MMU support since 80386, IIRC. So I think GPs claim might be inaccurate. But it wasn't a security feature, it was a productivity feature. It pr
by wyldfire 5y ago
MSDOS did have MMU support since 80386, IIRC. So I think GPs claim might be inaccurate. But it wasn't a security feature, it was a productivity feature. It protected your programs from defects in other programs and vice versa. This helps programmers find defects during design and helps users for defects that escape testing.
- spc476 5y ago[citation required] for the MMU support of MS-DOS.
- ok123456 5y agohttps://en.wikipedia.org/wiki/Control_register https://en.wikipedia.org/wiki/Control_register
- spc476 5y agoJust replying with a web page showing the 80386 has having control registers doesn't imply that MS-DOS used them in any meaningful way.
- ok123456 5y agoThe MMU is inside the processor. Any operating system running on an 80386 or higher has set registers/tables and gets hardware provided memory management.
- shadowofneptune 5y agoIf it uses it. Later versions of DOS did very little with the features the 386 offered, which is why there were MS-DOS extenders. https://en.m.wikipedia.org/wiki/DOS_extender https://en.m.wikipedia.org/wiki/DOS_extender
- ok123456 5y agoYou can make your own minimal DOS Extender just by setting those registers. This is what some games did.
- lproven 5y agoDR and MS DOS 5 and later have a 386 memory manager which can put an x86-32 CPU into Virtual 86 mode, remap RAM over any unused blocks in the I/O and ROM area (between 641kB-1024kB) to make Upper Memory Blocks, and load small resident parts of the OS into those blocks in order to keep as much base memory (0kb-640kB) free. These memory managers could also turn the extended memory (above 1024kB) into managed XMS or EMS memory. LIM EMS was accessible to DOS apps and XMS to DOS-extender apps. These were killer features in 1990 or so, and I made good money from optimising DOS memory for clients around that time.