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I tried using my own simple malloc by calling this bios function. Again in MS-DOS real mode. This bios function returns a 16 bit number and I don't really know if my code is correct to convert it to the actual address: word _malloc(word para){ word addr = 0; asm mov ah,48h asm mov...

I'm adding joystick support for my engine, and It is simpler to read joystick and keyboard at the same time after waiting for vsync. All keyboard functions and info I find, suggests I should read 0x60 port by inserting a custom function in interrupt vector 9. Will there be any problem with the...

I read this old post about EGA: https://forum.vcfed.org/index.php?threads/ega-video-corruption.43557/post-585123 I tried modifying EGA PEL panning without waiting for vsync, and my attempt to make a wave effect failed (Dosbox, PCem, 86Box). So does this mean all emulators are wrong?. I can't...

I want to improve a VGM player I made for PC/XT. VGM files (most of the time bigger than 64KB) must be processed in order to be even faster to play. To do that, I need to read the files byte by byte using fread(), then process every byte, store in ram, and read the next byte. If I use a buffer...

Is it possible to get the VGA card to output a full screen 320x200 at 60 hz? (Instead of the default 70hz). I could get 320x240 60hz with black bars at the top and bottom, but it does not look very good. Why do I want 60hz?. Because it is more compatible with emulators, and monitors, and it...

HI, I want to create a small .com program using the tiny memory model, but I don't know how to access video ram (in text mode) to draw some ascii "images". I'm writting stuff to vram using pointers like this: unsigned char *TILE_MAP = (unsigned char *)0xB8000000L; // this points to VRAM Then...

Hi, I read about how MCGA can load fonts for the text mode, but I did not find any clear example of how to do it. This Howard the Font is supposed to do it, but I just don't understand what it's doing. Here they point to a book which tells how to do it: "Richard Wilton's book covers MCGA very...

Hi. I wonder if the system palette in windows 3.1 can by modified. I'm using VGA driver (640x480 16 colors), so the graphics card can do it. According to windows 3 docs, the system uses fixed colors which can't be modified by programs, also if I wrote a little program to change VGA registers, it...

Hi, I just finished a tiny demo for MS-DOS, it only requires 8088 4.77, VGA and Adlib. Source code: https://github.com/mills32/Tiny-Demo My code is not very clear, but i'm sure it will inspire someone to make something with it, or improve the code because my sprite simulation is not very...

I'm trying to get cool effects by using text mode and uploading custom tiles/fonts to VGA. I already tested custom fonts on mode 3, and also changed cell size to 8x8, and disabled horizontal spacing so that 8x8 tiles fill the whole screen without vertical lines. That results in 640x400...

In the future, I might want to create a small case (Amiga style) for a 286 12 Mhz pc, and it will only fit there if the ISA cards (VGA, SBLASTER and sd card/HD adapter) are located in weird horizontal positions, parallel to the motherboard (and on top of it), also far from the ISA connectors...

I recently discovered geoworks for ms dos, and I love it. I wanted to customize it a bit by editing icons. I found some utils to create dummy icons for files and dos programs, but there is no way of editing the system program icons (preferences, text editor) for version 2.0. Only found editors...

I want to know (or calculate) the number of CPU cycles a VGA scanline takes to be drawn. I'll do it for 8088 and 8086 only, because 286 is fast enough to wait for scanlines (reading the vga ports). I don't think there is another way to synchronize code with the crt display. Any ideas on how to...

Hi. I was looking for samples of tandy graphics, and I read it can map any ram address to 0xB800 00000. I didn't find any samples explaining how to do this, can it really map any address to that video ram?. If so, it would be able to do basic hardware scrolling, even if horizontal scrolling...

Hi. How can I view or dump the VGA video ram to an image using emulators, or from ms-dos itself? Dosbox debugger worked perfect with "MCGA" mode, in which every pixel is a byte in memory. But the results with mode X games were not good. I converted the dump to an indexed 256 colour image, and...

So I continue programming a game engine for dos, and one of the last things I'd like to add, is a sound player (for sound blaster and compatibles). My goal is to use a 64K block to store tiny samples (sfx, and a few drums for music at 11025 and 8000 Hz), so that the engine can play them very...

I made a very simple adlib music player that plays imf files using interrupts. Some emulators and real PC's have no issues. But dosbox and some PCem configs (that use 386+ CPU's) just crash and the emulator hangs. Dosbox shows this error: "PIC: 4 byte interval not handled" Maybe I'm doing...

I'm trying to program a roto zoom for slow computeers like 8086 8 Mhz. I got it working in mode x , by copying data from an image in ram to vram in asembly, but it is still too slow, even with precalculated sin/cos stuff, the effect runs at about 10 fps. So I decided to do it the easy way...

I want to test some ideas in EGA video card but I can't find a lot of info about it. For the moment I can load images to vram in mode 0D, to create a background, and now I want to draw sprites on top of it. I know how to copy and restore the background every time a sprite is redrawn, but I...

Hi. Despite a lot of bugs, and things poorly implemented, this is working better than I expected. An 8086 - 8 MHz should run it OK. I captured this video using DosBox Daum at 600 cycles (more or less an 8086-8 ). You need a GUS card to play the MOD files. I tried not to be a mess with the...