Has anyone tried the PC1512 driver on a real system? If so, I'd like to get feedback on a couple of details.

Does the border (overscan area) of the display stay black when switching from graphics to text mode, such as when viewing inventory (TAB key)? The border flashes white briefly in PCem, which may be an emulation issue, but I have a relatively easy fix if the issue applies to real systems as well.

Does the screen shake look okay? Due to limitations of the hardware, I use the display start address instead of display position, which is not ideal but better than nothing. I'm not sure that emulators get it right, and a video clip would be great for verification, if possible. SQ2 has some screen shaking near the start of the game when Roger enters the shuttle and when the shuttle crashes on the planet.

ripsaw8080 wrote on 2026-02-07, 17:37:

Well, you must already be aware from SCI0 that the 40-column text drawn in graphics will be illegible, so do you view it as just an academic exercise?

I managed to make an AGI driver for the Olivetti PC1.
You can read more about it here. Re: The big Olivetti Prodest PC1 thread - i hope

The text is actually fully readable — but the issue isn't what you'd expect from SCI0. AGI and SCI0 handle text differently.

In AGI, game graphics (vectors, sprites, fill areas) go through the overlay's blit routine and display perfectly in 16 colors. The text situation is more nuanced: the AGI interpreter draws status bar and dialog text via INT 10h BIOS calls, which write directly to VRAM bypassing the overlay. Since the BIOS thinks it's in CGA mode 4 (2 bits per pixel) while the V6355D is actually in 16-color mode (4 bits per pixel), you get colored fringing — cyan and red pixels at character edges where two adjacent 2-bit values get merged into one wrong 4-bit color. It's a format mismatch, not a resolution issue.

The characters themselves are all there and legible — you can read the score, the input line, the dialog boxes without any trouble. The fringing is cosmetic. And a fix is possible (an INT 10h hook that re-renders characters in proper 4bpp format using the ROM font), we just haven't prioritized it yet since the graphics — which is 95% of what you're looking at in an AGI game — are perfect.

So no, not an academic exercise — these are fully playable. Seven games working in 16 colors on the PC1.

The non-intense red and blue seem too bright, and intense red looks magenta (quite noticeable on Gwydion in KQ3). N0t sure how or why it's mapped that way, but I think the idea should be for it to look as close to standard 16 colors as possible.

BTW, most AGI games use different interpreter versions in different releases of the game, and the original driver files tend not to be interchangeable due to specific addresses determined when they were compiled with the interpreter. By my count there were 18 interpreter versions released.

ripsaw8080 wrote on Yesterday, 17:37:

The non-intense red and blue seem too bright, and intense red looks magenta (quite noticeable on Gwydion in KQ3). N0t sure how or why it's mapped that way, but I think the idea should be for it to look as close to standard 16 colors as possible.

BTW, most AGI games use different interpreter versions in different releases of the game, and the original driver files tend not to be interchangeable due to specific addresses determined when they were compiled with the interpreter. By my count there were 18 interpreter versions released.

Thanks. Yes the colors are a bit off, i have adjusted and upload new images.
Adjusting the colors are easy since the palette on the PC1 is 512 colors.

I have made overlay files for the Sierra AGI games i have, they are all in the same .zip file. In the readme.txt is says to contact me for other overlay files.

The same trick (set mode 4, switch to 160x200x16 with register writes, map the palette accordingly) would probably work for other games with CGA composite graphics. I've experimented with that before using the Tandy machine type in DOSBox, but the games don't always make it easy to get away with. 😉

See this post: Re: The big Olivetti Prodest PC1 thread - i hope

TL;DR: would it be possible to make a variant that tweaks the 16-color palette on the Prodest PC1 to be more like that on the Atari ST and Amiga ports of AGI adventure games?

digger wrote on Today, 09:19:

See this post: Re: The big Olivetti Prodest PC1 thread - i hope

TL;DR: would it be possible to make a variant that tweaks the 16-color palette on the Prodest PC1 to be more like that on the Atari ST and Amiga ports of AGI adventure games?

Already did almost that:
CGA Palette Loader for Olivetti Prodest PC1
A tiny DOS utility that loads custom RGB palettes for any CGA games on the Olivetti Prodest PC1. The PC1 uses the Yamaha V6355D video chip with a programmable 16-entry RGB DAC.
https://youtu.be/uqIDscWm9C0

I have also made a TSR version that works with more games on ordinary VGA and EGA adapters. My video on that will be released April 10th. https://youtu.be/c2lrBGcd43Q
It has an option for using preset palettes from the Amstrad CPC, C64, ZX Spectrum and the CGA palette. The user can add more palettes with a .txt file.

I am also working on the CGA Composite TSR. Maybe i could add the same option there. This far in the project i am only using the CGA composite and EGA color palette. I could easily make an option for other palettes, og even let users decide, like in my PalSwapT.com.

Follow my channel to be updated.

Ah, that's even better! Thanks, and good job! 😃