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Re: DR-DOS 3.41 and CD-ROM drives

Posted on 2022-06-24, 11:49

Exploit wrote on 2022-06-24, 11:46: And that was a couple of years earlier! I would try NWCDEX nevertheless. But what should i do with the error message of UDVD2 earlier? I don't think you need to use UDVD2... Just use one of the other CD drivers plus NWCDEX from e.g. DR DOS 7.

Re: DR-DOS 3.41 and CD-ROM drives

Posted on 2022-06-24, 11:31

It might just simply be that DR DOS 3.41 doesn't support CD drives. It was released in 1989, which would suggest it might be possible. After all, MS DOS 3.1 could already run MSCDEX and support CD-ROMs, from what I read on Wikipedia. And that was a couple of years earlier! I would try NWCDEX …

Re: SVGA/VESA programming

Posted on 2022-06-24, 10:19

is it because they opted for explicit MCGA support? 64KB MCGA doesnt have banks or chained modes (EGA compatibility) so there is no way of implementing hardware scrolling (offsets) or page flipping. I doubt it because MCGA was used only on VERY few and slow machines. They would have not been able …

Re: Vogons Video Announcement Thread

Posted on 2022-06-23, 20:18

in Milliways
Recording MIDI Music onto Floppies I was asked by a viewer if the Roland SoundBrush that I showed in an earlier episode can also be used to record MIDI music from a PC. And yes of course, it can. With some caveats though! I connected the SoundBrush to my 486 PC and tried a few games. Lucasfilm games …

Re: SVGA/VESA programming

Posted on 2022-06-23, 06:37

Honestly, I also like 640x400 very much. Has a neat memory size. As Jo22 said it can be used down to 256K VGA cards, has higher refresh rate, and is very similar to other 400 line modes (which includes 320x200, which is line doubled on VGA). That's right, I often forget about this. 🙂 So mode 100h …

Re: SVGA/VESA programming

Posted on 2022-06-23, 06:35

I think I found the code for blitting blocks of changed screen data in LBA1: https://github.com/2point21/lba1-classic/blob … S_PHYS.ASM#L225 It includes VESA bank switching. Maybe this can be an inspiration to you, @WhiteFalcon?

Re: SVGA/VESA programming

Posted on 2022-06-22, 14:35

Honestly, I also like 640x400 very much. Has a neat memory size. As Jo22 said it can be used down to 256K VGA cards, has higher refresh rate, and is very similar to other 400 line modes (which includes 320x200, which is line doubled on VGA).

Re: SVGA/VESA programming

Posted on 2022-06-22, 11:51

Ok, I double checked, and for the 320x200 MCGA video mode they indeed rep movsd the whole FB to the screen: Mcga_Flip proc uses esi edi mov esi, Log mov edi, Phys mov ecx, 64000/4 rep movsd ret Mcga_Flip endp 64000/4 means ModeX, right? No, it means 320x200, but not mode x in this case, as they use …

Re: SVGA/VESA programming

Posted on 2022-06-22, 11:50

Good find! I was just searching for the source code of LBA. I remember the whole screen only changed on demand or when necessary, yes, but the sprites moved around constantly without any noticeable artifacts. Also the game required only 512kB vram which in itself means no double buffering (not in …

Re: SVGA/VESA programming

Posted on 2022-06-22, 09:12

Ok, I double checked, and for the 320x200 MCGA video mode they indeed rep movsd the whole FB to the screen: Copy code to clipboard 1 Mcga_Flip proc uses esi edi 2 3 mov esi, Log 4 mov edi, Phys 5 6 mov ecx, 64000/4 7 rep movsd 8 9 ret 10 Mcga_Flip endp

Re: SVGA/VESA programming

Posted on 2022-06-22, 08:51

Ouch, a typo, yes, it should have been less than 1/4. Probably had too high expectations forgetting how even commercial games had trouble on the 486. Games like Little Big Adventure or Transport Tycoon definitely redrew the screen for every frame and must have employed very optimised assembler …

Re: SVGA/VESA programming

Posted on 2022-06-22, 06:56

Or is it okay to draw all the screen for every frame? Background, sprites and all? It did work in VGA 320x200, I think even on a 486, but that was less than 1/2 of the pixels. I am afraid it would give me like 5-10 FPS on the Pentium, if even that many. You have to try. I always use this double …

Re: SVGA/VESA programming

Posted on 2022-06-21, 14:53

I have always read that "mul" is too costly and that one should avoid using it when possible. So I went for "shl"s to compute the coordinates into one offset and then loops to get the bank nambur. But as you say, it is a deditated instruction. Still, I am probably failing to explain my goal - I …

Re: SVGA/VESA programming

Posted on 2022-06-21, 11:27

I have always read that "mul" is too costly and that one should avoid using it when possible. So I went for "shl"s to compute the coordinates into one offset and then loops to get the bank nambur. But as you say, it is a deditated instruction. Still, I am probably failing to explain my goal - I …

Re: SVGA/VESA programming

Posted on 2022-06-21, 08:26

Nice code! Let me try to understand it: PUTPIXEL PROC push dx So the main magic is in this function. It takes the pixel position in variables loop1 (Y-coord) and loop2 (X-coord). As we mangle DX we need to save it. At the moment it is not clear what is in DX to me. mov ax,1280 mul word ptr[loop1] …

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