Wow, that's cool! I had no idea! Thanks for the information! 😁

Btw, if you need something to test -> Olivetti/Logabax/AT&T/Toshiba 640x400 hi-res graphics mode

Found a few mode utilities.. It's not much though, sorry. Please try to set CGA and 400 line mode.

I suspect this card is "VGA 1024C" or "Expert VGA", and these are the correct drivers:
https://files.retropc.se/hardware/DISPLAY/OTHER/XPERT_1.zip
https://files.retropc.se/hardware/DISPLAY/OTHER/XPERT_2.zip

But no, nothing about "AT&T" there either, and after setting the CGA mode, the options to set 200/350/400 scanlines are unavailable.

There's something in the datasheet about unlocking the "AT&T/M24 Reg" at 3DEh, but I can't get it to work, I guess I should read carefully through the entire datasheet... heh, maybe later...

Grzyb wrote:

There's something in the datasheet about unlocking the "AT&T/M24 Reg" at 3DEh, but I can't get it to work,
I guess I should read carefully through the entire datasheet... heh, maybe later...

That's good to hear! Maybe we get help by fellow vogons users here. Some of them are really good coders.
Perhaps all we need to do is to enable that register after the card was set o CGA. 😀

Edit: I've also got an "Olivetti" labled PVGA1 card (related to WD90C00) with Olivetti BIOS..
Maybe this will be useful later on ?

Jo22 wrote:

Edit: I've also got an "Olivetti" labled PVGA1 card (related to WD90C00) with Olivetti BIOS..
Maybe this will be useful later on ?

Do you have the software for that card?

Some other Western Digital chips also claim support for AT&T video, notably the ubiquitous PVGA1A, found eg. on the Paradise VGA Plus card.
However, the Paradise products catalog only mentions that card's compatibility with VGA, EGA, CGA, MDA, Hercules and MCGA.
The video mode utility (VGAPLUS.EXE) doesn't have any "AT&T" option, either.

Looks like they implemented that capability in their chipsets, but never bothered to provide software support.

I did some more experiments...

After reset, in VGA mode, reads from 3DEh return FFh, port obviously unavailable.
Then I set CGA mode using VGA1024C.EXE, and reads from 3DEh return 00h, but whatever I write in there has no effect.
Then I unlock the AT&T/M24 register:

0Ch -> port 3CEh
port 3CFh or 80h -> port 3CFh

From now on, writes to 3DEh indeed seem to have some meaning...
setting bit 2 (Character Set Select) makes all the characters empty, clearing that bit returns to normal
however, setting bit 0 (AT&T Mode Enable) seems to have no effect, it remains in text mode, and whatever AT&T graphics software I run, it stays in text mode as well

Either I'm missing something, or there's something wrong with that chipset, maybe a bug they never bothered to fix, as nobody was complaining...

Grzyb wrote:

Either I'm missing something, or there's something wrong with that chipset, maybe a bug they never bothered to fix, as nobody was complaining...

Same here. On the other hand, however, why did they at WD even bother to mention that mode so often then. In about all its flavours, M24, AT&T, AT&T 6300 etc.

Anyway, I've put together the most important bits of the '11 datasheet.
Maybe we're just missing something. 🙁

More experiments, this time with AST-VGA card, based on PARADISE PVGAIA chip (same as PVGA1A ?), with 256 KB of RAM, for 8-bit ISA.
In other words: a typical OEM variant of Paradise VGA Plus.

And the results are pretty much identical as with WD90C11A - by default writes to 3DEh have no effect, I can unlock this register so that toggling bit 2 changes the character set, but nothing more - AT&T graphics software fails to init the graphics mode.

Did you try going to CGA 640x200 gfx mode before hitting the AT&T mode bit?

Or try to set mode 40h using the int 10h call?

Ahh, so this may be the problem...

AT&T graphics software uses BIOS to init the graphics mode 40h, doesn't it?
This WD BIOS obviously doesn't implement that mode - "mov ax, 0040h / int 10h" has no effect, no matter if in VGA or CGA mode, with 3DEh locked or unlocked.

I can set mode 06h (640x200x2), and then run the AT&T 640x400 software, but it keeps running in 640x200, ie. only displaying every other scanline.

So, if WD chipsets are OK, and the only problem is with WD BIOSes not supporting mode 40h, then the solution is obvious: write a TSR to provide that video mode...
Now, how do I init the 640x400 mode without using BIOS? What are the proper values for CRTC, and other registers?

check this out: http://www.bitsavers.org/pdf/olivetti/m21_m24 … ation_Nov84.pdf

I guess you have to enable compatibilty mode, enable the AT&T register, make sure the 24MHz clock is selected, and then set CRTC registers as per the Olivetti manual (it has a chart with the settings)

edit: guess I should mention, the video info is in part 5 of the PDF

Thanks a lot for the tip! 😁

I'm going to do some more experiments next week.
Meanwhile...

Jo22 wrote:

I've also got an "Olivetti" labled PVGA1 card (related to WD90C00) with Olivetti BIOS..
Maybe this will be useful later on ?

Can you try setting mode 40h via int 10h on that card?

It's possible that WD supported the AT&T/M24 mode in their chipsets especially for Olivetti, and while other OEMs (eg. "AST-VGA" and "Expert") didn't bother supporting it in their BIOSes, the Olivetti BIOS may actually have the support.

Grzyb wrote:

Can you try setting mode 40h via int 10h on that card?

Hi, I'm sorry, I'm still looking for that particular card.
It must be somewhere in the attic, if I haven't sold it already.

Anyway, I also found another PVGA BIOS that was part of the Olivetti M250E system.
Maybe it works. It's attached and contains some other stuff (first one of 3 parts in one file ?)

Also interesting.. https://pcem-emulator.co.uk/phpBB3/viewtopic.php?t=804

Seems like Olivetti GO481 graphics board was based around a Paradise PVGA1A chip.

Edit: Luckily, I also found this BIOS file.
HI/LOW as well as a merged and limited file are attached.

Okay, so I used LDGFXROM in DOSBox and sucessfully loaded up the 32KiB GO481 BIOS in Paradise machine mode.
So far, programs using SVGA and VGA seem to work. MSD also reports the BIOS date and so on.
That being said, maybe some extra work has to be done making the file compatible with other stuff (filling unused space with FF etc).

Ahhh... Mission Supernova. I remember that game. Crappy programmer artwork, but I took every adventure game I could get.

root42 wrote:

Ahhh... Mission Supernova. I remember that game. Crappy programmer artwork, but I took every adventure game I could get.

Did you ever find out how that one guy was able to enter that restaurant with his shoes on ?

Grzyb wrote on 2019-06-29, 18:54:

Jo22 wrote:

I've also got an "Olivetti" labled PVGA1 card (related to WD90C00) with Olivetti BIOS..
Maybe this will be useful later on ?

Can you try setting mode 40h via int 10h on that card?

I have a PVGA1A card in my 286-based AT&T (Olivetti) system and it works with 640x400x2 mode inits. I disassembled the Paradise VGA BIOS on that card to learn why, and found that the BIOS will redirect any int 10h calls setting the mode to 40h (640x400x2) to the host BIOS. So, to answer the mystery, these cards don't actually fully support 640x400x2 on their own because they rely on a host AT&T computer to set the mode properly.