Which method for enabling the A20 line works in DOSBox?

Posted on 2022-10-09, 21:21

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by videogamer555

in DOSBox Development

in DOSBox Development

After reading how complicated this is (for something so commonly used on any modern CPU that it should NOT be this complicated), I'm wondering which method of enabling the A20 line that DosBox uses. Here's the article I read about how to program in ASM to activate the A20 line. http://www. …

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Re: Does DOSBox support 32-bit "unreal" mode?

Posted on 2022-10-09, 20:13

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by videogamer555

in DOSBox Development

in DOSBox Development

Every time I try to use a 32-bit memory accessing instruction, it says "illegal opcode", because it thinks I'm trying to use a 32-bit memory access instruction in 16-bit real mode. It doesn't seem to realize that I've switched to what's basically 32-bit real mode. You are still in a 16-bit mode, so …

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Does DOSBox support 32-bit "unreal" mode?

Posted on 2022-10-09, 12:31

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by videogamer555

in DOSBox Development

in DOSBox Development

I was reading about how to get 32-bit memory access in real-mode, and discovered there's a hidden mode called "unreal" mode, that's not actually an official mode. It works like this. You set up the global descriptor, load the GDT, switch to protected mode, set the data segment register so that it …

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Re: How do I enable Composite Video mode for CGA?

Posted on 2022-10-09, 12:19

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by videogamer555

in DOSBox General

in DOSBox General

konc wrote on 2022-09-27, 07:37: Use SVN version and press F12. But it's not perfect Untitled.png Isn't that the version I need to compile myself, because it's only available as source code?

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How do I enable Composite Video mode for CGA?

Posted on 2022-09-26, 23:42

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by videogamer555

in DOSBox General

in DOSBox General

I notice when I start DosBox it says at the top that I can change the hue with F11 (or Alt+F11). However, it doesn't say how to enter composite video mode. Here's a screenshot of when it starts up https://i.imgur.com/HpM2Hl9.png And yes, I read the readme file, just like that message box says for …

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Re: Scaling problem with a 1440p (with 320x200 games)

Posted on 2022-02-13, 03:07

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by videogamer555

in DOSBox General

in DOSBox General

FulValBot wrote on 2022-02-04, 20:28: So i have to change desktop resolution to "fix" this... Doesn't DosBox have a "stretch to fit" option for full screen mode that will stretch the game's screen to fit your monitor, even if this distorts the proportions of the graphics in the game you are playing …

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How many MB of VRam are emulated in DosBox?

Posted on 2022-02-13, 03:02

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by videogamer555

in DOSBox General

in DOSBox General

I'm writing 16bit software in NASM that includes the needed opcodes to switch to VESA video modes, including 640x480 256 color mode. I am discovering that DosBox doesn't do well with that mode. It doesn't let me use any more VRAM than needed for 640x400 256 color mode (80-pixels shorter in the …

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Re: Why can't DOS (from a boot disk image) find the emulated CD drive?

Posted on 2022-02-13, 02:53

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by videogamer555

in DOSBox General

in DOSBox General

You may as well just copy the contents of the CD to a subdirectory. Except that in some OS's they EXPECT real CD access. Like they try to read from the CD with CD access commands (or even if they don't do that, they are hardcoded to either read from drive D, or they are hardcoded to look in the …

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In response to https://www.vogons.org/viewtopic.php?p=1039982#p1039982

Posted on 2022-02-13, 02:46

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by videogamer555

in DOSBox General

in DOSBox General

@Jo22 I wanted to reply to your comment at https://www.vogons.org/viewtopic.php?p=1039982#p1039982 but the thread in which this comment existed was a locked thread, so I'm putting my response here. Why doesn't DosBox just store emulated file system structures in their own files like the emulated …

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Re: Is there such a thing as a usb-to-serial mouse converter?

Posted on 2022-02-13, 02:36

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by videogamer555

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

(PCB factories do NOT make these at cheap prices for small quantities). You're right, $7 is pretty expensive for a production run of five 4-layer PCBs. Surely out of my reach. https://i.imgur.com/E7yHCUU.png $7 is a "special price" it says. That's just to sucker you in to using their service. Most …

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Re: Have you guys considered adding PC-98 mode?

Posted on 2022-02-13, 02:26

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by videogamer555

in DOSBox Development

in DOSBox Development

Intel was emphasising the 8 bittedness of the 8088 externally so as to court system designers who thought 16 bit was scary and who otherwise might have banged out another Z80, or 6800 system. So I was right in that it could only read/write 8 bits of RAM at a time, even if it could internally …

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Re: Have you guys considered adding PC-98 mode?

Posted on 2022-02-13, 02:09

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by videogamer555

in DOSBox Development

in DOSBox Development

The hardest part of emulating PC-98 is probably the graphics and/or sound hardware. Less difficult but still something that would need to be done would be to add features to the DOS (software) side of DosBox (rather than the hardware emulation side). For example, DOS (and possibly the BIOS ROM as …

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Re: Why can't DOS (from a boot disk image) find the emulated CD drive?

Posted on 2022-02-13, 01:52

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by videogamer555

in DOSBox General

in DOSBox General

not sure I would call it a PC emulator as its only emulating hardware required to run DOS and none of it is 100% correctly emulated, its more of an OS emulator for DOS, its certainly no WINUAE which I would happily throw into the PC emulator category. Its really its own thing not fully one or the …

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Re: Why can't DOS (from a boot disk image) find the emulated CD drive?

Posted on 2022-02-13, 01:49

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by videogamer555

in DOSBox General

in DOSBox General

DOSBox provides CD support by emulating mscdex, not by implementing IDE hardware so loading an operating system means there will be no CD detected. If it's emulating MSCDEX driver, why can't the copy of Windows running in DosBox use the emulated driver? Why doesn't DosBox present the emulated …

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Re: Why can't DOS (from a boot disk image) find the emulated CD drive?

Posted on 2022-02-13, 01:46

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by videogamer555

in DOSBox General

in DOSBox General

As already mentioned, regular DOSBox (including SVN) has no support for IDE devices and is only meant for running DOS games. If you need this functionality you should have a look at DOSBox-X which has IDE support and just happens to also support Windows 95 and 98. Actually since HDDs are on the IDE …

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Re: Why can't DOS (from a boot disk image) find the emulated CD drive?

Posted on 2022-02-13, 01:44

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by videogamer555

in DOSBox General

in DOSBox General

It is a PC emulator, it just doesn't emulate every little piece required for correct win95 operation. not sure I would call it a PC emulator as its only emulating hardware required to run DOS and none of it is 100% correctly emulated, its more of an OS emulator for DOS, its certainly no WINUAE …

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Re: Setting video memory in VGA registers broken.

Posted on 2022-02-02, 18:07

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by videogamer555

in DOSBox Development

in DOSBox Development

One thing I discovered trying new graphics modes and ideas for FastDoom is that you can't rely on DosBox emulation, it's not up to the task. PCem behaves better, but still misses some quirks from real hardware. Just try on real hardware. For example I developed an Hercules 640x200 mode that worked …

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Re: Setting video memory in VGA registers broken.

Posted on 2022-02-02, 12:34

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by videogamer555

in DOSBox Development

in DOSBox Development

Maybe you can try with DosBox-X or PCem, both are better than DosBox. I was just hoping to know if in DosBox official version, if this is a known intentional "feature" for it to have this limit of 64KBytes of VRAM? Or is this actually a bug? I know that Dosbox is only meant for games, but I was …

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Setting video memory in VGA registers broken.

Posted on 2022-02-01, 14:52

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by videogamer555

in DOSBox Development

in DOSBox Development

I'm trying to use the http://www.osdever.net/FreeVGA/vga/graphreg.htm#06 register's memory map select field, and the http://www.osdever.net/FreeVGA/vga/seqreg.htm#04 register's external memory available bit, in order to boost the available amount of VRAM (emulated VRAM in the case of DosBox) in …

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Re: Question about DOS 16 color modes.

Posted on 2022-02-01, 02:15

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by videogamer555

in DOSBox General

in DOSBox General

Thanks. I'll have to check that out. I also discovered something. If I set the chaining bit in graphics card sequencer register 4. It does something quite interesting (at least in DosBox, not sure about real hardware). It changes it from the normal EGA image-planar mode (where you have to select …

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