# Win32 .dlls question

**URL:** <https://discourse.libsdl.org/t/win32-dlls-question/1006>\
**Category:** SDL Development\
**Created:** [July 26, 1999, 3:24pm UTC](https://discourse.libsdl.org/t/win32-dlls-question/1006 "1999-07-26T15:24:39Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Lorenz\_Pollak](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/l/96bed5/32.png) [@Lorenz\_Pollak](https://discourse.libsdl.org/u/Lorenz_Pollak)\
**Post date:** [July 26, 1999, 3:24pm UTC](https://discourse.libsdl.org/t/win32-dlls-question/1006/1 "1999-07-26T15:24:39Z")

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Hi to everyone in [SDL]!

This might be a silly question, but I hope you don’t mind, if I ask…

I began writing an application with SDL on my linux-system and everything was  
fine and worked well. Then I wanted to test my app at my friends computer who  
runs Win32 and so I compiled it with the ming32-crosscompiler-package. But then  
when we run my app, it somehow was terribly slow, although our machines are  
pretty the same. (K6/233 Processor)

By accident I found out that if my app uses only SDL-dib.dll (I killed  
SDL-dx5.dll) it runs with the desired velocity (or at least much faster). When  
does SDL use SDL-dib.dll (and what stands dib for?) and when does it use the  
other dynamic library SDL-dx5.dll (which as I suppose uses the  
directx-interface)?

And how come those differences in velocity?

thanks for your answers,  
Lorenz

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**Author:** ![Michael\_Vance](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/m/f4b2a3/32.png) [@Michael\_Vance](https://discourse.libsdl.org/u/Michael_Vance)\
**Post date:** [July 26, 1999, 3:38pm UTC](https://discourse.libsdl.org/t/win32-dlls-question/1006/2 "1999-07-26T15:38:16Z")

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> does SDL use SDL-dib.dll (and what stands dib for?) and when does it use the

DIB = device independent bitmap, a data structure that Win32 GDI (I think) uses  
for blitting.

> other dynamic library SDL-dx5.dll (which as I suppose uses the  
> directx-interface)?

Right.

> And how come those differences in velocity?

Who knows? I should think that DirectX would run much faster. Was DirectX 5 or  
greater installed on your friend’s machine? Was it using accelerated device  
drivers?

m.On Mon, 26 Jul 1999, you wrote:

–  
“How wonderful! How mysterious Programmer  
I carry wood! I draw water!” Loki Entertainment Software

- Anonymous Tao poet

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**Author:** ![Vaclav\_Slavik](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/v/8797f3/32.png) [@Vaclav\_Slavik](https://discourse.libsdl.org/u/Vaclav_Slavik)\
**Post date:** [July 26, 1999, 5:27pm UTC](https://discourse.libsdl.org/t/win32-dlls-question/1006/3 "1999-07-26T17:27:03Z")

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Lorenz Pollak wrote:

> By accident I found out that if my app uses only SDL-dib.dll (I killed  
> SDL-dx5.dll) it runs with the desired velocity (or at least much faster). When  
> does SDL use SDL-dib.dll (and what stands dib for?) and when does it use the  
> other dynamic library SDL-dx5.dll (which as I suppose uses the  
> directx-interface)?

SDL-dib.dll uses Windows low performace but generic functions for bitmaps blitting  
etc. while SDL-dx5.dll uses DirectX which is optimized for best performace in  
multimedia apps.  
SDL application detects available interfaces at run time and prefers DirectX. If  
SDL-dx5.dll is not found or DirectX is not installed on the system, it uses DIB.

> And how come those differences in velocity?

DIB is much slower than DirectX.

Vasek

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**Author:** ![Vaclav\_Slavik](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/v/8797f3/32.png) [@Vaclav\_Slavik](https://discourse.libsdl.org/u/Vaclav_Slavik)\
**Post date:** [July 26, 1999, 9:09pm UTC](https://discourse.libsdl.org/t/win32-dlls-question/1006/4 "1999-07-26T21:09:57Z")

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Warren Downs wrote:

> > Lorenz Pollak wrote:
> > 
> > > By accident I found out that if my app uses only SDL-dib.dll (I killed  
> > > SDL-dx5.dll) it runs with the desired velocity (or at least much faster).  
> > > When \> does SDL use SDL-dib.dll (and what stands dib for?) and when does it use  
> > > the  
> > > other dynamic library SDL-dx5.dll (which as I suppose uses  
> > > the \> directx-interface)?  
> > > SDL-dib.dll uses Windows low performace but generic functions for bitmaps  
> > > blitting  
> > > etc. while SDL-dx5.dll uses DirectX which is optimized for best performace in  
> > > multimedia apps.  
> > > SDL application detects available interfaces at run time and prefers DirectX.  
> > > If SDL-dx5.dll is not found or DirectX is not installed on the system, it uses  
> > > DIB.  
> > > And how come those differences in velocity?  
> > > DIB is much slower than DirectX.  
> > > Vasek
> 
> But for him, DirectX was slower. That’s what he was surprised about. My guess  
> is, DirectX wasn’t using accelerated drivers, or wasn’t even installed(?)

Oops. Time to have some sleep before answering mails… .Sorry

I think SDL checks whether DX is installed or not (as I looked at the code when I  
wanted to find out how it really works under MSW). And you won’t be able to run it  
with SDL-dx5 if DX wasn’t installed, so probably some dirty drivers as you said…  
VS

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**Author:** ![Warren\_Downs](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/w/ed655f/32.png) [@Warren\_Downs](https://discourse.libsdl.org/u/Warren_Downs)\
**Post date:** [July 26, 1999, 9:51pm UTC](https://discourse.libsdl.org/t/win32-dlls-question/1006/5 "1999-07-26T21:51:46Z")

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> Lorenz Pollak wrote:
> 
> > By accident I found out that if my app uses only SDL-dib.dll (I killed  
> > SDL-dx5.dll) it runs with the desired velocity (or at least much faster).  
> > When \> does SDL use SDL-dib.dll (and what stands dib for?) and when does it use  
> > the  
> > other dynamic library SDL-dx5.dll (which as I suppose uses  
> > the \> directx-interface)?  
> > SDL-dib.dll uses Windows low performace but generic functions for bitmaps  
> > blitting  
> > etc. while SDL-dx5.dll uses DirectX which is optimized for best performace in  
> > multimedia apps.  
> > SDL application detects available interfaces at run time and prefers DirectX.  
> > If SDL-dx5.dll is not found or DirectX is not installed on the system, it uses  
> > DIB.  
> > And how come those differences in velocity?  
> > DIB is much slower than DirectX.  
> > Vasek

But for him, DirectX was slower. That’s what he was surprised about. My guess  
is, DirectX wasn’t using accelerated drivers, or wasn’t even installed(?)

Warren