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List:       linux-msdos
Subject:    Re: sound support (Re: XMS problem with Aladdin demo)
From:       Bart Oldeman <bartoldeman () users ! sourceforge ! net>
Date:       2005-03-13 5:09:17
Message-ID: Pine.LNX.4.58.0503131740120.5832 () enm-bo-lt ! localnet
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On Tue, 8 Mar 2005, Ryan Underwood wrote:

> BTW, would OpenGL support be better for vgaemu?  It seems that on the
> SDL mailing list, OpenGL is suggested in all cases for 2D operations for
> performance reasons.

I looked at OpenGL some time ago, trying to figure out how dosbox uses it.
dosbox only uses it for scaling and from what I gather it only really
helps on NVidea cards but not ATI for instance.

If there's no scaling necessary, for instance if you run dosemu fullscreen
in X and the resolution matches 1:1, OpenGL won't help at all.

In general, where OpenGL really helps is if you can send objects
(textures) to VRAM and manipulate them there. The uploading of the
textures is the slow part.

And this is what dosemu does all the time... suppose MITSHM is active and
we're on a local box there are three buffers:
1. emulated video memory (e.g. 320x200 2bpp)
2. X pixmap (e.g 640x400, say at 32bpp)
3. real VRAM. Same format (mostly) as 2.

Now most of the X rendering business is to transform 1. to 2. Even if
you'd use opengl you'd still need a 1 to 2 step, but one could skip the
scaling -- bpp still needs to be transformed.

2. to 3. can be very fast using DMA sometimes even, it depends on a lot on
the X server and the graphics card.

So personally I see OpenGL as quite a bit of work for very little gain ...
and it doesn't help I use an ATI card myself.

> It's true.  I've been preparing a ready-to-run DR-DOS image based on the
> Caldera hdimages of 7.03, but I'm not sure if it is okay to redistribute
> it with the SCO problems.

There have been mirrors of it... But in general it won't work. It's
non-commercial use only, binary only, SF would never allow it.

A long time ago (James MacLean era) DOSEMU tried to work out something
with the then owners of DRDOS but it really didn't work out (long story).

The only way to work around FreeDOS issues is to fix them. So this is
is what I did for quite some time.

> Isn't it possible for a BSD port too?  Anyway, I see a lot of people
> trying to run DOS games under Linux with e.g. dosbox and qemu and
> complaining about the speed => Linux sucks, etc.  This is the marketing
> problem I'm talking about.

You just need a developer interested in a BSD port. There hasn't been one
for the last 8 years or so.

> Fortunately you have been around for the meantime.  I try to fix bugs
> and add little features here and there but I have no capability to make
> architectural decisions.

All I can say at this point is that by this point dosemu (even 1.2.2)
works well enough for me, as compared to what I wanted to contribute when
I started participating (just after 1.0.0 was released). In a way that's
good, in another way it's bad (for you! not me). Since it removes much of
the motivation to work on it.

DOSEMU became more and more of a pet project, and I've slowly realized
that I should let it go. Imagine what I can do with all the new time, say
- socialize with local people
- do more about sports, be a healthier person
- if I'm programming do so on projects more relevant to my job
- no more arguments with Stas! Yay! ;-)

Bart
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