I finally figured out how it calculates travel times.
It's the difference in X coordinate between the two cities, plus the difference between the Y coordinate, plus one.
that quantity divided by 40, then has 2 added. if the result is over 7, it's set to 7.

Weird! that's not how you measure distance, Carmen.

TODO: plot all the distances between all 30 cities and compare how inɐccurate this mess is

also, it's the 90s, I can afford a sqrt().
I should fix it up for my version.

or use a squared lookup table. you could do this REAL easy by making it a table search: there's only 6 possible results: 2,3,4,5,6,7. each entry in the lookup table contains the maximum squared distance that can generate that number of hours

here's all 30 city locations:https://gist.github.com/foone/0992517879877e0e995259d08a0941a7

it's currently way too 6am to do more calculations, though. I'll do that tomorrow

Good news: @modulusshift did the calculations for me!

https://digipres.club/@modulusshift/113924878526681049

I think that says that it doesn't matter much. The biggest error is in the biggest distances, which are all saturated to the max of 7-hours anyway.

PUSH ES
PUSH AX
RETF

why must you hurt me, carmen sandiego?

I'm confused by the graphics detection routines. I thought it was returning 0 for "no graphics" or something, but it turns out 0 means MCGA.
So the GraphicsMode enum goes:
0: MCGA
1: CGA
2: Hercules
3: EGA
4: Tandy
5: VGA
6: ???

I don't think there's any reason why this would support SVGA. It always use 320x200 at a maximum of 256 colors. VGA is more than enough to handle it

being able to do a textual find-replace on VRAM is a weird but occasionally useful ability

I find-replaced the background from palette entry 0 to palette entry

Now I can confirm how big this image is. Previously it was set into a black background, which made it harder

worst thing that could happen just happened:

I just realized the portable Where in the World is Carmen Sandiego? is based on the same version I'm hacking, meaning it's in-scope for me to get this, dump the ROM, and compare.

That just increased the cost and complexity of this project by bunch

WAIT HOLD ALL THE PHONES.
Here's a photo from a MS-DOS version. It does that thing some companies (like Sierra) did back in the day, and included both 3.5" and 5.25" disks in the package.

BUT WHY ARE THERE SO MANY DISKS?

The copy of this game I have is approximately 470kb! You could fit this on ONE disk!

ARG, they mislabeled this.
Admittedly, this isn't really their fault, this is confusing shit.

This is the 1992 Where in the World Is Carmen Sandiego? Deluxe, not the 1990 Where in the World Is Carmen Sandiego? Enhanced.

okay I finally found a boxed copy of the Enhanced 1990 DOS edition. (confusingly labeled the 1993 edition)

It comes on two 5.25" disks: presumably double-density, so that's 720kb in total.

Floppy Disk Pop Quiz: What's weird about these floppies, specifically given that this is MS-DOS version?

I happened to look at mobygames, and noticed two interesting things.

First, the Mac version is very similar to the DOS version, other than the expected changes you'd get from it being on a monochrome system with a GUI.

But wow, that's a completely different font! Is that built into macs or something? (EDIT: @amr confirms it is)

(also, the dialogue box is top-aligned. DOS bottom-aligns them)

Secondly, the TurboGrafx-16 version didn't even THINK about using the same GUI!

I don't want to go through a million platforms but all the other ports of this game tweaked some art here and there or put in different location-photos, but all of them have the same basic tall-window-on-the-left, smaller-window-in-the-top-right, four-buttons-in-lower-right design

The answer for "what's wrong with these floppies?" is that they're double-notched. That's needed for double-sided disks... on systems which have single-sided drives!
The PC has basically always been double-sided, so they only need one notch, on the top/a side.