montezuma iii wrote on 2025-10-22, 23:05:

And of I bring the PC to a cellular phones repairing center: aren't them equipped for removing SMDs?

I seriously don’t know, haven't been in such places yet. Just passing by on street.
Depends on how experienced and thoughtful the person in question is, I guess.
And how accurate they work, if they do value vintage tech and treat it with respect.
Where I live, such cell phone shops are often being run by Turkish people I think..
Not sure if they have a link to western retro culture..
That's all I can say, I'm afraid.

But again, not sure if a removal is even needed.
Making the chip invisible to the PC is good enough already, maybe.
That way, the PC could be restored easily once again.

montezuma iii wrote on 2025-10-19, 21:11:

I'll not remove It, but I don't understand if the reason is because It needs a special skill (I'd eventually had brought to a co […]
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Predator99 wrote on 2025-10-18, 16:21:

To repeat again: Do _not_ remove that IC 😉

I'll not remove It, but I don't understand if the reason is because It needs a special skill (I'd eventually had brought to a competent/skilled person) or because the entire pc will have a string of troubles? Or maybe because

Predator99 wrote on 2025-10-18, 16:21:

So its a nice chip supporting Plantronics, other people are seeking for cards supporting this.

?, but I think my VGA should emulate CGA/EGA graphics.

quote=Jo22 maybe it's enough to gently lift a single power pin of the IC to disable it?

Which is the Pin to lift?
Again, Predator99: should I lift the pin on the chip, or It is harmful/damaging?

Hi and Happy New Year to all the community:

1) Could I try to lift the power pin of the GPU or is unuseful? (I have a second frael board to try)
2) Could I try to remove the video ROM ?(not the GPU)
3) I think there are only a few game using VGA and supporting the NEC V20 CPU, right?
4) Could I try with an EGA card, or It's unuseful?

Thanx
Regards

A happy new year to you, too! 🥳

montezuma iii wrote on 2026-01-01, 22:16:

3) I think there are only a few game using VGA and supporting the NEC V20 CPU, right?

Um, it depends.. Some EGA/VGA games from the 90s have an 80286 check routine, some run fine, some have no working keyboard.
The latter is because the AT platform had introduced a dedicated keyboard controller that some games/applications try to talk to.

The XT had some serial i/o chip and did keyboard protocol in software, basically.
So that means software which assumes an AT keyboard controller doesn't work.
A Joystick on gameport might still work in such a case, not sure.

This website has a list of Windows games that run on 8088, V20, 80286 or higher:

https://win16.page/

(Windows 3.0 still runs on XTs in Real-Mode.)

My Frael King PC 's maximum memory is 768k, so these games are out of its possibility (they requires at least 1MB)

montezuma iii wrote on 2026-01-03, 22:16:

My Frael King PC 's maximum memory is 768k, so these games are out of its possibility (they requires at least 1MB)

Um, but I've run several smaller Windows 3.0 games on a PC/XT with 640 KB, even on CGA/Hercules.
That "1 MB" probably just means that they don't have any special memory requirement.
An ordinary PC/AT (XT was niche) from 1990 onwards had no less than 1 MB minimum installed (640 KB base + 384 KB extended).
If no or only a little Extended Memory was available then because the extra RAM was used otherwise for Shadow Memory.
To copy BIOS and VGA BIOS into the RAM for faster access.

1) Mine has 768k on the mainboard installed as microchips, I don't know if, maybe, I can install an isa card with 1 Mb RAM, if the pc will see It
2) What about the others questions?

montezuma iii wrote on 2026-01-03, 23:24:

1) Mine has 768k on the mainboard installed as microchips, I don't know if, maybe, I can install an isa card with 1 Mb RAM, if the pc will see It
2) What about the others questions?

1) You could carefully try to lift the power pin of the CGA chip by carefully touching it with a knife and the tip of soldering iron..
But I would practice first on something else. Some electronics from the parts bin, maybe.

2) The video ROM. On a normal CGA/Hercules cards, the ROM merely holds a text font.
There's no video BIOS stored inside, since both CGA and MDA (Hercules in text-mode) have the required code in PC BIOS.
On EGA/VGA it is different. Here the video ROM stores a copy its own video BIOS, such as the VGA BIOS.

4) The EGA card behaves similar to a VGA card.
Both have a video BIOS, both use A segment (640KB to 704 KB) and B segment (704 to 736 KB).

https://zaage.it/projects/upgrading-a-ibm-pc- … -b-704k-to-736k

The CGA uses the B segment for framebuffer only, that's why it can co-exist with the MDA and Hercules card.

The Hercules uses the unused memory location between 704 and 736 KB for a 32 KB video page (in socalled "half-mode").

If no CGA card is installed, it can use two of them (Hercules has 2x 32 KB).
That's why CGA emulators can work with a Hercules card: the other video page is where CGA would be.

So games can write to CGA location, SIMCGA can read the pixel data,
convert it to Hercules and copy it to the other video page that's visible (currently set as active).

.. and if none of this memory location is in used by these devices, a VGA card can function normally.

That's long story short, basically.

But there's one exception, maybe.: Depending on the smartness of the VGA BIOS,
it might detect that B srgment is in use
and then the VGA card might be set up in a way to care only about A segment and leave B segment alone.
That means that VGA/MCGA modes are available on the VGA card, while CGA graphics are left to the CGA card.

But I'm just guessing here. There's a bit more than just framebuffer space.
VGA and CGA modes use different CRTC registers, too.
So the VGA card should not try to touch the CGA registers like it normally would if it was the only graphics card in the system.

PS: There's another "problem", maybe.
If the XT has full RAM expansion, then there's contiguous RAM from 1 to 736 KB (convention memory or DOS memory), plus another 32 KB of CGA RAM (CGA uses 2x 16 KB).
So the A segment in 640 to 704 KB is already "full", in principle.
Not sure how a VGA card would react to that. Maybe it would..
a) have its RAM mapped to A segment, anyway. Then both RAMs are being written to/read from same time
b) it would disable its own RAM and take system RAM instead
c) realize there's no free framebuffer location and refuse to work

In short words an EGA card will outputs black/white video as the VGA, because It has a BIOS too?

montezuma iii wrote on 2026-01-04, 00:56:

In short words an EGA card will outputs black/white video as the VGA, because It has a BIOS too?

I'm not sure, to be honest.
User mkarcher knows more about such things.

In principle, lifting the power pin should leave the integrated CGA like "a dead fish in the water".

Edit: But that depends on how the IC works internally.
If it's floating (-not grounding-) its own other pins, then it should become a passive, invisible component.
Any CGA address decoding etc should become disabled, the CGA RAM should become invisible, too.

Then, an EGA/VGA card might just boot up normally.

Provided that the fully expanded RAM doesn't cause further issues.
The 640 to 704 KB range is normally "empty" on later PCs.

Merely late XT era PCs had been fully upgraded to 704 or 736 KB,
because CGA/Hercules were still common graphics standards, still,
with their framebuffer being naturally absent from A segment.

No, I meant if an EGA card outputs black/white video if installed without disabling the internal CGA

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