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I don't understand why they gave up on DOS compatibility for 64-bit Windows.. the effort could not have been all that much for them (either with an emulator or
by jhallenworld 13y ago
I don't understand why they gave up on DOS compatibility for 64-bit Windows.. the effort could not have been all that much for them (either with an emulator or x86 tricks). The benefit is huge: they can continue the lock-in of ancient DOS programs. For example, I can report that OrCAD for DOS works better in 32-bit Windows XP better than it ever did in MS-DOS.
Likewise, I don't understand why vm86 mode can not run directly from 64-bit mode in x86. This seems very like an architectural mistake to me.
- MBCook 13y agoAs I remember, when an x86-64 chip is running in 64 bit mode, it can run 32 bit code, but the option necessary to run in 16 bit mode was removed. To run DOS they'd basically have to have a full emulator for a 286, like a limited version of bochs.
- ciupicri 13y ago> > Why can't you just run the 16-bit emulator from 32-bit Windows in the 32-bit emulator on 64-bit Windows? > [Because that emulator uses v86-mode, which is not supported by 64-bit processors. -Raymond] -- http://blogs.msdn.com/b/oldnewthing/archive/2013/10/31/10461992.aspx#10462321 http://blogs.msdn.com/b/oldnewthing/archive/2013/10/31/10461...
- nknighthb 13y agoI don't know what mechanisms they use, but VMware's various products run 16-bit code just fine on x86-64 chips. Are you saying they added a full 286 emulator to their virtualization products?
- pgeorgi 13y agoEssentially yes. But I guess they simply kept their virtualization code from pre-hardware virtualization times around. 286 shouldn't require much maintenance :-)
- ateeqs 13y agoMmmm, I think it's just not profitable for them to do this any more.