There are so many variations of Dos Simcity that it's hard to know for sure, but is that not the EGA high resolution mode of 640x350? If so, that's going to be a narrower picture than either 320x200/320x240 or 640x400/640x480.

Yes, it is the EGA high resolution mode. That must be it then.. the non-standard resolution does not work properly with the aspect ratio correction, which is designed for the standard 640x and 320x resolutions? I expect there is no way to get around that then, apart from playing it in the lower resolution mode. Or leaving aspect ratio correction off and playing in widescreen mode, which while less accurate is at least more pleasing to the eye.

A while ago there was an in-depth topic about the various resolutions and what they looked like on real 4:3 CRTs. Here it is:
The Quest for Pixel Perfect DOS Emulation

I won't pretend that I understand the reasons why some video modes would stretch to cover the whole screen while others won't, but one of the examples was the main menu screen from Lemmings which is 640x350, and the topic author showed that it was centred on the 4:3 screen and not stretched with a real DOS CRT display:
https://imgur.com/UNIzK8O

I have not the slightest idea if this applies to all games that run in this resolution, but since applying aspect correction to SimCity results in obvious vertical stretching, maybe this was the case as well? That, or the DOS version devs just didn't care.

DOSBox doesn't emulate the display timings in much detail. I know with lemmings and some other games that have a resolution of 640x350, that a more accurate framing is to center it vertically in a 640x400 resolution. On a real VGA this is done through display timings by manipulating the active pixels and the front/back porch.

DOSBox-X, PCem and some other PC emulators do attempt to emulate the display more accurately and they might give you a better result with the right settings. In DOSbox, you would set the scaler to "normal2x" and then force the resolution to 640x400 to achieve the effect - or dial in a custom resolution for DOSBox to use if you have a CRT monitor or an LCD that is accommodating.

Aspect ratio correction is broken for EGA modes in DOSBox, that's the only issue here.

To be more specific, there is a known issue with the aspect correction of 350-line modes when using the machine=ega setting, which includes text modes due to the 14-line font. However, I'm not aware of any compelling reason to use the EGA machine type for original SimCity.

The attached screenshots in the first comment of this thread seem to show the aspect correction working as intended. There are countless posts on this forum questioning the results of aspect correction because the graphic elements of certain games do not appear to be square or round as expected. It's usually because the graphics elements were designed with a square-pixel mode rather than the non-square-pixel mode the game uses. Dungeon Keeper is a classic example, with its image of a CD shown while the game is busy loading data and its radar display in the upper left of the screen -- seems like they ought to be circles, and they are when aspect is not corrected, but they become ovals when aspect is corrected.

ripsaw8080 wrote on 2021-05-27, 20:40:

To be more specific, there is a known issue with the aspect correction of 350-line modes when using the machine=ega setting, which includes text modes due to the 14-line font. However, I'm not aware of any compelling reason to use the EGA machine type for original SimCity.

OK, however just for the record, my machine type is set to svga_s3. I had selected the high resolution EGA mode from within the SimCity installation settings.

almeath wrote on 2021-05-28, 03:50:

OK, however just for the record, my machine type is set to svga_s3.

I guessed that was the case because your screenshots with aspect=true already have the "proper 4:3 ratio" you asked for, so I'm trying to explain that for the purpose of aspect correction the aspect ratio refers to the display area and not what game developers choose to depict within the display area. 😉

ripsaw8080 wrote on 2021-05-28, 04:36:

almeath wrote on 2021-05-28, 03:50:

OK, however just for the record, my machine type is set to svga_s3.

I guessed that was the case because your screenshots with aspect=true already have the "proper 4:3 ratio" you asked for, so I'm trying to explain that for the purpose of aspect correction the aspect ratio refers to the display area and not what game developers choose to depict within the display area. 😉

That makes sense, thanks. In SimCity, I like the 16 color EGA mode because I find the 256 color VGA at 320x200 too chunky and low res for my tastes. I am quite happy to play this game in a stretched wide screen format to get proper proportions in the graphics.