How many MB of VRam are emulated in DosBox? \ VOGONS

How many MB of VRam are emulated in DosBox?

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First post, by videogamer555

Posted on 2022-02-13, 03:02

videogamer555 Offline

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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 vertical direction than 640x480). When I load a 640x480 image it doesn't load all the pixels.

Does DosBox not fully support high-res VESA modes? Is it limited to 256000 bytes of VRAM?

Reply 1 of 2, by jmarsh

Posted on 2022-02-13, 03:21

jmarsh Offline

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You didn't think to check the memory size returned in the VESA information?

Reply 2 of 2, by _Rob

Posted on 2022-02-13, 18:23

_Rob Offline

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With the default S3 Trio64, dosbox defaults to 2MiB VRAM. And standard dosbox does not have a setting to modify this.

Some forks have a "vmemsize=" option where you can specify other sizes. For instance for DOSBox-X, have a look at this wiki:
https://dosbox-x.com/wiki/Guide%3AVideo-card- … OSBox%E2%80%90X

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