What version of TangoPCB Plus are you using?

You could try checking out this thread VESA display problem with Tango PCB

There they mention version from 1992 and my searches on Google turned up version 2.30 from 1994.

napierm wrote:

I added:
videoram=2048

Where and why?

The program is Tango PCB Plus version 2.02. I will try to see what version that 1992 program is and if the VESA .drv files can be had but not holding out much hope. I seem to remember these tango builds were very different from each other.

Looking at that thread he seemed to be having different problems and the version of dosbox also seemed quite different. But I will try to contact him and see. Thanks for the catch.

The videoram statement is right under machine in [dosbox] and is supposed to increase the amount of video ram. It didn't have any affect.

Also in [sdl] all the "output" settings have no effect.

napierm wrote:

The videoram statement is right under machine in [dosbox] and is supposed to increase the amount of video ram.

Not in my version of DOSBox 0.73.

MiniMax wrote:

napierm wrote:

The videoram statement is right under machine in [dosbox] and is supposed to increase the amount of video ram.

Not in my version of DOSBox 0.73.

Yeah that doesn't sound like an official DOSBox feature to me.

And the ET4000 can address only 1MB 😀

Shed some light on the issue: I have a CAD application that suffers from the same problem at 1024x768. The problem also occurs on a real hardware ET4000. However, on a real hardware ET3000 it works. Not so using svga_et3000 in DOSBox, so there is an issue left.

I read some old threads and tried a few settings. Not too surprising then that with the new version that setting is obsolete.

I never had a et3000 card. I used a few different et4000 ones ending with one that will do 24-color. It was a lot of fun doing ray-tracing and displaying the results. In 1992 that was a big deal and very hard to find a way to get a nice hard copy. A professional photo-printer turned out to be the cheapest way.

Anyway, I think you're right, there is a bug remaining in the Tseng driver.

Surprise, the vesa drivers from 2.3 *do* work with my 2.02. Tango will run in vesa mode under dosbox up to 1280 with no problems.
😎

Shed some light on the issue: I have a CAD application that suffers from the same problem at 1024x768. The problem also occurs on a real hardware ET4000. However, on a real hardware ET3000 it works. Not so using svga_et3000 in DOSBox, so there is an issue left.

There were quite a few apps quickpatched from ET3000 to ET4000. ET3k generally could not address more than 512K and had only 3 bits for bank switching (actually 3+3 as Tseng could set read and write banks simultaneously). ET4k supported 1024K and used 4 bits but the bits had to be shuffled a little in order to work at all. That required very simple binary modification. Unfortunately, those apps still used only three bits for bank switching so modes with more than 512K still did not work. To make it more confusing, some configuration programs actually listed modes that were not internally supported. All of that led to one of two glitches -- either invisible bottom third of the screen or that bottom drawn on the top.
That said, WHATSVGA has some glitch in current ET3k emulation so it may well be that there is a bug there. I was somewhat out of the loop recently -- Real Life(tm) -- but it's on my plan to take a look into it.

I think the ET3000 uses the full 128k a000-bfff in its SVGA modes. The CAD application does not touch the banking register.

With a Hercules card installed along the ET3000 the Hercules will show gibberish when the program is started 😀

There was a trick with 128K banks on ET3000 but I could not find any documentation for it beyond the reference to the high bits of bankswitch register as 128K bank toggle. SVGA documentation is surprisingly sparse. I used Ferraro's book and the text file that came with WHATVGA and neither of these sources even mentioned the fact that ET3k and ET4k use different byte ordering in mode 13h.