DOS ain't dead

I'm trying to port some patch from one VXD to another VXD (a different driver version). I started with comparing patched and original file. At the beginning there are 3 different bytes at offset 144-146h - what is its meaning?
The file starts with MZ signature and common DOS stub.
LE header start with LE signature at offset 80h. I guessed that bytes are LE checksum but not, it's 0. I found some LE description but it didn't went too further to describe offset bytes at 144h - 80h. Any idea?

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DOS gives me freedom to unlimited HW access.

Hello RayeR,

> The file starts with MZ signature and common DOS stub.
> LE header start with LE signature at offset 80h. I guessed that bytes are
> LE checksum but not, it's 0. I found some LE description but it didn't went
> too further to describe offset bytes at 144h - 80h. Any idea?

No idea, but perhaps the bytes starting at offset 0x144 are part of some other data structure which the LE header (before them) refers to?

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https://gitlab.com/tkchia · https://codeberg.org/tkchia · 😴 "MOV AX,0D500H+CMOS_REG_D+NMI"

> No idea, but perhaps the bytes starting at offset 0x144 are part of some
> other data structure which the LE header (before them) refers to?

Yes, it maybe. Is there any description of (headers of) Win9x VXD files?

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DOS gives me freedom to unlimited HW access.

Some info is here:
https://www.geoffchappell.com/notes/windows/archive/vxdldr.htm

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DOS-u-akbar!

I didn't much oriented in that document but I got an idea, that the DWord at offset 144-147h must be some image size or code segment size because the patched file contains 56 new bytes of code in a cavity at the end of file and the difference of this magic DWord between original and patched version is aslo 56 so without this change Win98 crashed probably because accessing code beyond the limit. So I fixed the magic DWord by adding 56 and let's see :)

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DOS gives me freedom to unlimited HW access.

I got a message that patched driver now works at least with 256MB card so it's on a good way, the DWord in header really matters...

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DOS gives me freedom to unlimited HW access.