Re:The Life of MS-DOS
by wyldfire on Sunday February 13, 2022 @03:46PM
(#30325492)
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.
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[citation required] for the MMU support of MS-DOS.
DR 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.
Just replying with a web page showing the 80386 has having control registers doesn't imply that MS-DOS used them in any meaningful way.
The MMU is inside the processor. Any operating system running on an 80386 or higher has set registers/tables and gets hardware provided memory management.
Re:The Life of MS-DOS
by shadowofneptune on Sunday February 13, 2022 @09:14PM
(#30327725)
If it uses it. Later versions of DOS did very little with the features the 386 offered, which is why there were MS-DOS extenders.