From: leathm AT solwarra DOT gbrmpa DOT gov DOT au (Leath Muller) Message-Id: <199705150046.KAA23687@solwarra.gbrmpa.gov.au> Subject: Re: OpenDOS graphics drivers To: pierre AT tycho DOT com Date: Thu, 15 May 1997 10:46:40 +1000 (EST) Cc: opendos AT delorie DOT com In-Reply-To: from "Pierre Phaneuf" at May 14, 97 02:04:12 pm Content-Type: text Precedence: bulk > > Even though a DOS 16bit program doesn't have scheduling to worry about, > > it still only runs at half the speed of a 32bit program; under NT and Win95 > > you can also set the priority of a program to 'real-time' which pretty much > > takes over the operating system completely. > 32 bit isn't double the speed of a 16 bit program! The *main* advantage > that you can access larger areas of memory at once. For example, you can > use a linear frame buffer, instead of using 4 segments and bank switching > to access the video card. This is a *bit* faster since you don't have to > bank switch, not because of using 32-bit instructions. Of course, using > 32-bit instruction will help a bit too. Under NT, an ordinary user cannot > set a priority to real-time BTW. Ok, first off, if 32 bit isn't that much of an increase, why aren't we all still using 16 bit? :) I just don't think there is any argument between the advantages/speed etc of 32bit and 16 bit... As for NT, a program run by a normal user (not the administrator) can update its priority to real time; it uses a hack though... Its basically a program dependent thing which I have seen running, I just have no idea how to do it... :) (Basically, the game sets itself to real-time priority, and then sets itself back to normal priority if alt-tab/alt-enter etc is hit) > > > There's a Quake version for S3 ViRGE chipsets, this is what you should > > > compare a WinQuake using DirectX 3.0 drivers, on the same system (using a > > > ViRGE video card, of course!). > > Are you talking about 3D acceleration in hardware? I Don't have that yet... :) > > I am talking sheer CPU power... > The only two advantages of DirectX is that it gives any program access to > all the features of hardware acceleration (which is interesting) and > overcome the GDI, which is a GUI-only concern, since there's no GDI to > overcome in DOS. Wouldn't it be great though if OpenDOS had access to all the features of hardware acceleration? I have written tests to check on the speed of DirectX blits from a backbuffer and software blits under DOS (even using the FPU load/store method) and windows still outperformed DOS... Now if I could use the hardware acceleration of my card in DOS, I'm sure it would outperform the windows stuff, but remember, a 640x480x32 framebuffer is 1,228,800 bytes; at 30FPS thats 36Mb to transfer - if you have hardware accleration moving that around for you, thats a lot of spare time for the CPU - more than the overhead of scheduling and task switching (if the game is the only thing running) Leathal.