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Considering MS-DOG (inside NTVDM) (Users)

posted by marcov, 04.08.2011, 21:59

> > OS/2 was supposed to be that OS, but IBM and MS couldn't agree on
> > direction. MS wanted to skip over the 286 and develop for the 386
> instead.
> > IBM said "No, we're developing for the 286." In retrospect, this was an
> error.
>
> Maybe it was an error to make the 80286 (mostly) 8086 compatible ? Or to
> keep the 64 KiB segment limit ? Or to invent M$-DOG and M$-Windaube (both
> were already out when OSama/2 started, and influenced it) ? Or to implement
> support for the old M$-DOG and M$-Windaube legacy crap in the new cool
> OSama/2 ? It's always easy to criticize historical decisions of other
> people :-)
This is afaik all known. IBM simply wanted to clear out 286 inventory, and keep the 386 at a premium for a time longer. Nice tiered pricing schemes as they were used to in mainframes.

Then Compaq started mass selling 386 clones, and being quite succesful at it.

> > While the 286 offered additional capabilities, it was essentially a
> > transitional step, and the 386 was a far better platform.
>
> So why did M$ and Boreland develop for 80286 for that many years (Win16,
> DPMI16) ?
Because it took some time for 386 to receive full penetration. Also the price of memory was still prohibitive. (and 386 OSes ate more memory).

> > While the 286 had features, it had limitations. Like you could only run
> > one "real mode" application at a time
>
> You could implement multitasking in RM too (maybe not that reliable) or use
> the new cool PM :-)
I'm not going to argue any of that. I simply don't know enough about 286 PM.

I did use it, but only to get more memory in Borland Pascal. I don't know much more than that you had to be very careful to not run out of (IIRC 8192) selectors. But that could be a dpmi/heapmanager limitations (allocating big blocks from the OS, eating up a selector)

> > and while there was an instruction to enter Protected mode, there
> > was none to leave it - you had to do a CPU reset.
>
> + no CPUID, no RDTSC/WRTSC, no CRC32, and the horrible 64 KiB segment limit
> :clap:
The 64kb thing was indeed horrible. Though some of the horrors were self inflicted in retrospect, like keeping to try assembler code running with different memory models (tiny/compact/large/huge etc)

Not being able to pass a pointer in a single register made register parameters hard.

> > In your position, I'd look at a VM solution, rather than trying to
> multi-boot
>
> The HORROR of booting DOS :clap:
It depends on the uses. If you do major compilation work, a VM is only slowing. OTOH that could be done under XP too, and there is no need for native dos.

So that leaves testing the result. I would do that on an old system, and not the new one.

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