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NTVDM speed (or lack thereof) (Announce)

posted by Rugxulo Homepage, Usono, 15.02.2011, 14:26

> I would not have mentioned the following in a DOS forum, but you kinda
> started me... For CPU bound apps, NTVDM indeed is awfully slow -
> independent of display mode.

I've never noticed any slowdown for reasonable apps, but so many things can come into play (e.g. cpu, e.g. redir -t befi.com on AMD64x2 Vista was 5x slower than without redir). It just depends, but for most normal uses, it's the same speed (for me, in my obviously limited experience). By design it's not supposed to be much slower at all, so if it is, something went wrong.

NTVDM is deprecated and they won't fix (almost?) any bugs in it, at least that's the impression I get (slightly more than an educated guess). So it wouldn't surprise me if it did fail in some way, but overall it "mostly" works (at least XP, maybe not higher). It's far from perfect but indeed sad that it's dead. It runs what even DOSEMU can't, sometimes.

> Under the virtual DOS box of Windows 9x, the slowdown if much less than NT,
> but still significant (unbearable for the lengthy calculations). Except of
> course unlike NT you /could/ CLI under 9x ;=)
>
> One more reason to keep our DOS living !
Just for the record, pre-emptive multitasking has always been more expensive than cooperative or none. And yes NT has a higher runtime footprint than 9x. Win95 could run in 4 MB, NT always needed at least 16 MB (I think??). And yes, DOS being ultra minimal (with no tasks or drivers or TSRs) means it's sometimes (but not always) better for benchmarking or doing intense calculations. paq8o8z ran equally as fast under NTVDM in my tests, but HX + Oxford OBC output + MSVCRT ran quite a bit faster under DOS than Windows. So it varies. (And I still don't know what happened with LZMA-FPC under NTVDM, never bothered testing further since nobody cared.)

NT was never meant for home users, and they dragged their feet forever before finally switching to it (more stable). We all (should) know that older NT versions really sucked re: DOS support. Well, compared to today, they lacked a lot in other areas too. Win2k/XP tried adding and fixing a few things, and while it could (and should) have been much better, it was still okay. I don't expect them to work miracles, it's just maddening when they won't fix simple things or even pretend to care. And before marcov says, "Why should they?", let me say: 1). there's more legacy than new stuff, 2). it doesn't hurt them at all, it's a benefit, 3). they (should) know DOS better than anyone, 4). an OS that runs less stuff is not more valuable (duh?), 5). why not? 90,000 employees all too busy? (doubt it)

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