First a double-check: UMC VGA chips certainly existed, but they were relatively rare, certainly in the VLB-era. Are you sure that you're looking at the VGA chip and not either the motherboard chipset or an I/O controller?

Secondly, drivers depend on the exact chip (regardless of vendor). Could you give us the exact chip model number? If it is a VLB UMC chipset it would be something like UM-85C418. If that's the case I doubt you'll find Win98 drivers, but there are Win95a drivers which may work:
http://www.video-drivers.com/companies/1097.htm
(note that I have no idea what's in that .zip, so scan for viruses/malware before doing anything with it)

UM85C418F-GP
9442A
N31478

Thank you very much...

When I searched for this driver in 2014 I could only find a malfunctioning one. Fortunately I later got the original Driver disks, which I uploaded:

486 VLB UMC-Chipset, what is it?
TK8498F 486 UMC VLB motherboard and I/O+VGA card

The UMC 418 Display driver is a Windows 3.1 one, meaning that you can still install it in Windows 95, but some dialogs will be missing, as well as switching mode without reboot. IIRC.

PS. A 486 is already struggling with Windows 95. Windows 98 has the 'Slow Explorer / internet Explorer integration', which will make the OS less responsive on a slow system like a 486. If you do insist on Windows 98, consider the 'Win95 explorer' transplant. Though just using Windows 95 would be my choice.

First of all, I thank you very much for your help. Do you know the technical features of this graphics card I use? Is it a Swvga card for example? How many megabytes of memory does the card have? Do you have information about jumper settings?

Thank you very much.

You're welcome.
All that I know about the UMC graphics card is in the topic and package I linked to. That includes a photo plus a scan of the manual. The manual shows jumper settings and a video mode listing. My UMC card had 1MB memory, no expansion sockets for more. Also my card is a combo card with multi-I/O controller and interfaces.

Hello again. Your card is different from the one on your side. They use similar processor, but card designs are different. I will install my system to Windows 95 tomorrow. I ask a lot of questions. Sorry. I just do not know much about this. There is not much information, especially related to older systems. The bottom part of my display and controller card is the same as the picture. I use 420mb Hard disk. It is set as Hard disk master via 40 pin IDE cable. At the same time the CDROM drive is also connected as Slave. These drivers are connected to this vlb combo card. The 5.25 and 3.5 drivers are also connected to the CPU controller of the UMC. There is no problem with the system. Each piece works fine. How should the jumper settings you see in the picture look like? What is HDC for example? What is Vga irq 9? Ideal bios should be open or closed? I used this card. I do not understand your settings.

HDC may mean Hard Disk Controller. I do not know much about the workings of VGA IRQ 9, but the manual says Default=off.
As for the other settings on your photos, I am afraid I am not familiar with these settings. Also they are described differently compared to the manual of my card. So I don't know what to suggest other then: just leave the jumpers as they were originally. Or search the internet for clues.

Post by gerwin » 2018-1-27 @ 15:08:

gerwin wrote:

When I searched for this driver in 2014 I could only find a malfunctioning one. Fortunately I later got the original Driver disk […]
Show full quote

When I searched for this driver in 2014 I could only find a malfunctioning one. Fortunately I later got the original Driver disks, which I uploaded:

486 VLB UMC-Chipset, what is it?
TK8498F 486 UMC VLB motherboard and I/O+VGA card

...

Dear gerwin,

Thank you very much for the manual of [85c418] you made available,
but unfortunately enough, its file:

[Manual_um85c418_partial.pdf]

with size 2,987,500 bytes included into:

[tk8498f_motherboard+vga+multi-io_v11.zip]

is just what it says its name, that is a part of the whole manual.

Would you, please, supply the rest of the manual up to its end?

Sincerely yours,

Petros EZ

I know,
Though I am not sure if I will put in time to do the rest. It took plenty of time to compile that 486 package already, especially since I am a perfectionist that removes all dust and scratches in scans....

Is there anything in particular you need to know about the driver setup?

Dear gerwin,

Thank you very much.

Well, for the moment, I am still waiting to get by post this rare card I ordered a week ago,
but I will may take advantage of your kindness and time if and when -hopefully soon-
it finally arrives...

But, it is obvious that you are a perfectionist indeed!
Hum... What could I do in return to this possible favor?
Hum... Lets see... Are you an engineer who has a somehow
deeper interest in rf, microwaves or antenna measurements?

Best Regards,

Petros EZ

Hello Petroz,
That is kind of you.
So I added the missing pages today:
TK8498F 486 UMC VLB motherboard and I/O+VGA card

Dear gerwin,

This is Great!

I understand.

Thank you so much,

Petros EZ

PS
I still owe you a favor.

You are welcome.

petrosez wrote:

I still owe you a favor.

No need, life is full of obligations already. The idea was kind anyways, and I am curious as to what RF measurements you meant, so it would be nice if you could give me a message (PM) about that. I have an electrosmog meter myself.

Yes, indeed : ) it is full of...

Anyway, I tried, but I got :

"We are sorry, but you are not authorised to use this
feature. You may have just registered here and may
need to participate more to be able to use this feature."

so I will send you a message to your "Current Email address".

- Well, it was delivered, I hope.