gerwin wrote:

as long as I destroyed and returned the harddisk,

I hope you don't mean physically destroy? 486 harddrives aren't that common any more and there is no need to physically destroy a harddive to get rid of the data on it. ActiveKillDisk and other software takes care of that.

feipoa wrote:

Could you use the existing barrell battery solder points for the CR2032 but cut the connection to the charging lead, similar to what I did on this motherboard, Native PS/2 mouse implementation for 386/486 boards using the keyboard controller

Wow, that is an interesting soldering project you have there. I will have to read all of that later.
Yes I was considerering scratching away the connection of the positive terminal and fixing the battery holder on two points. But I did not feel like scratching the board.

I removed the CR2032 from its holder, and moved the old barrel battery into the holder instead. This gives me the same circuit, but with 4 Volt instead of 3. Now it is keeping the time properly again! I will see tomorrow, but so far it points to the CR2032 voltage being the problem.
There seems to be 3,6V version for sale: LIR2032. Worth a try, right?

vetz wrote:

I hope you don't mean physically destroy? 486 harddrives aren't that common any more and there is no need to physically destroy a harddive to get rid of the data on it. ActiveKillDisk and other software takes care of that.

Sorry, but yes. The previous owner was really serious about the data being unrecoverably gone. It was the main reason for that system still standing there. Returning a smashed disk was the only thing I could think of to convince a 'less computer savvy' person.

That looks like a pretty typical layout for a VL Bus board with 3 VLB slots regardless of manufacturer or chipset. I have a few of them packed away that look very similar. I was binge buying 3 VLB slot motherboards for a while when 486 boards were still cheap. 🤣

gerwin wrote:

Glad you like it.
I suppose old hardware is much more useable with the proper documentation and/or drivers. So storing and sharing what we still have is a great idea.
Look what I found: UMC Computer IC Data book 1990/1991. If only it was the 1993/1994 edition...

Oh, I didn't mean to imply that it's impossible to find UMC documentation, just fairly uncommon. 😉

sliderider wrote:

That looks like a pretty typical layout for a VL Bus board with 3 VLB slots regardless of manufacturer or chipset. I have a few of them packed away that look very similar. I was binge buying 3 VLB slot motherboards for a while when 486 boards were still cheap. 🤣

Good investment for sure.

Stiletto wrote:

Oh, I didn't mean to imply that it's impossible to find UMC documentation, just fairly uncommon. 😉

Yes, it had to be somewhere, otherwise there would have been no way to design motherboards with UMC chipsets.

I received the Atmel EEPROMs, and I am now disappointed. They can be hotflashed with a Slot-1 board, and verify OK. but when I put them in the 486 Motherboard, the power leds turn on, but nothing happens, no beeps, no display...
I tried three differen BIOS files, including the original one. I tried the 64kB chip and also did a "copy /b 64kB.rom+64kB.rom 128kB.rom" and put the result on the 128kB chip. The 5V Vcc power is already connected to pin 32. Not a clue on what is preventing the EEPROMs from working...

PS. One of the BIOS files I tried is actually for the Pine PT-430 mainboard. This Pine board is almost identical in layout to the TK 8498F, but has much better documentation. Link.

I found and fixed the problem with the Atmel 29C512 EEPROM! 😀
I was probing the status of the three mode-select pins of this chip when installed on the 486 motherboard. Pin 31 'Write enable' must be set high, meaning that the BIOS chip is not to go in write-mode. The motherboard does not do this properly. Putting 5 Volt on that pin makes it work.

gerwin wrote:

I found and fixed the problem with the Atmel 29C512 EEPROM! 😀
I was probing the status of the three mode-select pins of this chip when installed on the 486 motherboard. Pin 31 'Write enable' must be set high, meaning that the BIOS chip is not to go in write-mode. The motherboard does not do this properly. Putting 5 Volt on that pin makes it work.

That's an impressive bit of hacking, well done!

Gerwin, i believe i have found the same AT upside down computer case.. I think you have the same because of>

* My case have the same style turbo LED thing..
* My case is also up side down one..
* My case also came with a UMC 8498F motherboard ( i found it had a 40 mhz cyrix inside, and an ch-498B rev 2.0 (made by chicony VLB motherboard)
* It also came with that same `brown / yellow` multi i/o VGA UMC card, that i mentioned earlier..

I also tested the bios from the dead one, it same that the old rom works perfect on the new working one, so i thing there is something wrong with the card it self..

Is that a recent acquisition, or did you just have it in storage?
This is my case, after removing all the dust. Nice and small. Is it still the same?

I attached a small heatsink to the VRM today. That thing gets hot, even when running a DX4 at 2x. Maybe I will make a bigger heatsink later.

The BIOS I settled for is this one: http://sannata.ru/bios/486/UM498F!.ZIP
It is an Award v4.50G BIOS from 09/08/1995. It has Write-Back/Write-Trough cache options, functional and adjustable Non-Turbo and better Harddisk detection.

As I understand Write-Back should give better memory 'moving' speeds in SpeedSys, the green line in the graphs. Unfortunately I am unable to make this work properly. If only there was someone with a better implementation of the UMC 498 chipset, willing to trace the cache control lines to the chipset: HITM# - CPU pin A-12 / INV - CPU pin A-10 / CACHE# - CPU pin B-12

Robin4 wrote:

* It also came with that same `brown / yellow` multi i/o VGA UMC card, that i mentioned earlier..
I also tested the bios from the dead one, it same that the old rom works perfect on the new working one, so i thing there is something wrong with the card it self..

According to this auction the card runs fine without a BIOS. I doubt it. 🤣
http://www.ebay.de/itm/181129530251
Why do some people remove BIOS chips from cards/motherboards, then offer them for sale?
It is now in Bulgaria, but the card still shows a Dutch Warranty sticker.

Anyway, I don't know what else to suggest to fix your broken VLB card.

Yes it was my latest recent acquisition. I bought it this saturday.. Mine case looks almost as new as it seems, yours is more yellowed.. And yes i can confirm its the same case.. Only mine turbo display is mounted on the outside of the metal case.. Mine case also have the pc-speaker inside that plastic hole thing in front of the metal case.. Also the case badge it different.. Its having a badge from vedicom (i dont know if it wouldnt say something to you) But the power supply is also a target one.. (think these are junk psus..)
My case only have a problem suddently, the metal bracket for screwing the cards in its original.. Because the expension cards dont sitting aligned in the slots..
Iam already thought about how to fix this.. Iam trying to modify the bracket a little bit so i can align it with the motherboard and case..

Robin4 wrote:

Yes it was my latest recent acquisition. I bought it this saturday.. Mine case looks almost as new as it seems, yours is more yellowed.. And yes i can confirm its the same case.. Only mine turbo display is mounted on the outside of the metal case.. Mine case also have the pc-speaker inside that plastic hole thing in front of the metal case.. Also the case badge it different.. Its having a badge from vedicom (i dont know if it wouldnt say something to you) But the power supply is also a target one.. (think these are junk psus..)
My case only have a problem suddently, the metal bracket for screwing the cards in its original.. Because the expension cards dont sitting aligned in the slots..
Iam already thought about how to fix this.. Iam trying to modify the bracket a little bit so i can align it with the motherboard and case..

Don't discriminate my case because it is more yellow then yours 😉. It had been standing near a window. Yours is like new indeed, good find.
The cases are technically exactly the same, just that mine is disassembled for cleaning. I put the turbo LED there for the photo, but it was placed behind the metal front in error. No problems with misaligned expansion slots here. Fortunately the expansion-slot-grid is a separate piece bolted to the back-plate.
Junk PSU?, if you say so. I am still using it actually. But the fan has been replaced. The original fan made a lot of noise, it was terrible.

I don't know Vedicom either. Many of the local computer assemblers from that time are gone now. I still have a brochure about "Innovator" 386s and 486s. Innovator was the brand of our 386-25MHz, which was later upgraded to a 486-66MHz.

How does the chicony ch-498B rev 2.0 compare to the TK 8498F? What are the jumper settings for the LED to display "40"?

This system got some attention again.
I wanted to try another video card, because the UMC Video chip had a few quirks:
- No Windows 95 driver, So one has to use the Windows 3.1 driver in Windows 95.
- Scrolling bug in Keen.
- Issues with the image quality, though I was not sure wheter it was the card or the attached cheap LCD screen.

At first an S3 card seemed most desirable, but this article changed my mind to Cirrus Logic: Nerdly Pleasures: Meet a Better Video Card. Since I am a fan of what Cirrus Logic produced for the Sound Card business in the 90's, it would be interesting to give their graphics card a try. Fortunataly the GD542X VLB series are quite abundant, as far as VLB cards go.
This is the one obtained, a CL-GD5428 based card with 2MB. It has the latest BIOS v1.41 already installed.

The new video card was of zero use for weeks, since the existing UMC Multi-IO+VGA controller cannot turn off its VGA part. It can only turn off the IO modules. This left me with no harddisk access when the CL-GD5428 was installed. At most I could verify it posted.
Yesterday this was solved by the arrival of a new Multi-IO card. Quite a nice one: IDEVL2M with ATronics-2015PL chipset. It is brand new in the box, with cables and documentation. It matches the offering from Boca research. They are still around it seems.

Before that I also read about the Cyrix 5x86 being able to do 1x multiplier. This would be very useful, as the 486DX4s are hard to slow down sufficiently for some older games. Death Track for example.
At first I feared such a CPU would not properly run on a mid-generation 486 motherboard, but some people here suggested it should.
Anyways; eventually found a Cyrix 5x86 100GP S1R3 for a reasonable price. The modded BIOS recognizes it properly, and it works very reliable so far. It remains close to the mighty intel DX4 in the graphics benchmarks. But the 1x multiplier is enough reason to replace the previously installed iDX4.
Cx5x86 support is planned for SetMul. Actually the development version does the trick already, but the CPU detection routines must be expanded before I can release it.

Yesterday I benched all the available CPUs and the two VLB graphics Cards. Using all possible multiplier settings and without changing a single thing in the BIOS or the startup configuration.
One thing about the UMC-418 graphics: It is like 7,3% faster then the Cirrus Logic. But considering its downsides, the CL-GD5428 is likely to remain installed. The UMC-418 scored 8,3 FPS in PCPbench when combined with the intel 486DX4-100 and 7,0 with the am486DX4-100.
The last SCORE column is just a quick and dirty attempt at normalizing the results to a single value: Done this way:
Score=((3DB1+3DB2)*0,35+PCPB1*2,9+PCPB2*6,57+Doom*1,08+Speedsys*0,96)/89,5
These scores are generally fine AFAIK. Take into account that Write-Back won't work properly with this motherboard, thus Write-Through mode was selected.
I have the feeling that of all the upgrades done on this system, the two 60ns FPM sticks were the best investment.

There is one disappointment with the CL-GD5428: It does not support graphics mode 100h (640x400x8) without the Univbe TSR. Note that Univbe v5.1 has the smallest memory footprint when adding new Vesa modes: v5.1=8,2 kB; v5.3=12,9 kB; v6.5=19,8 kB.

I had the same mainboard in a "multimedia" computer sold by Neckermann (Germany). It didn't have the same Multi-I/O card though, the I/O card had a UMC chipset and there was a CL-GD5424 with 1 MB. CPU was the UMC 486 with 40 MHz, which wasn't a bad performer for an SX.

That is a sweet case. I would love to find one like that for my 486 project box but can never find one when I'm looking. They seem to be rarer than hens' teeth these days.

oerk wrote:

I had the same mainboard in a "multimedia" computer sold by Neckermann (Germany). It didn't have the same Multi-I/O card though, the I/O card had a UMC chipset and there was a CL-GD5424 with 1 MB. CPU was the UMC 486 with 40 MHz, which wasn't a bad performer for an SX.

You remembered that well. 😀 Obviously they also put a lot of UMC components in that setup.

snorg wrote:

That is a sweet case. I would love to find one like that for my 486 project box but can never find one when I'm looking. They seem to be rarer than hens' teeth these days.

Maybe it is also because computer-cases are kinda large for shipping, and therefore less suitable for ebay and such.
I am not in any hurry to put the components in their case, it would make it harder to swap cards and CPUs.

Here is a shrunk version of the Video Card test in Computer Gaming World no. 125 Dec 1994. The text colors are my doing.

What is funny is the Speedstar Pro CL-GD5428 score, it is exactly the same as my card combined with the am486DX4@66MHz: 3DBench = 47,60 FPS. The exact same benchmark from 1994 was thus recreated in 2014. How useful is that 🤣

Looking at these scores, it shows that a CL-GD5428 is pretty close to what is the maximum framerate in DOS. At least for 320x200 mode. It is in windows that other cards can give a significant boost.

gerwin wrote:

Note that Univbe v5.1 has the smallest memory footprint when adding new Vesa modes: v5.1=8,2 kB; v5.3=12,9 kB; v6.5=19,8 kB.

New favorite: Univbe v5.0=5,5 kB; This one is VESA 1.2 only. Univbe v5.1/5.3 are VESA 2.0 and v6.5 is 3.0.

Gerwin, what software did you use to create your motherboard layout?

An older version of Adobe Illustrator: v9.0, from 2000.
Starting with importing a photo of the board, which is locked in the background layer. Then use layers on top of that, to draw the shapes and add the text.
When it is done I save one version as PDF, with the background photo removed.

gerwin wrote:

Looking at these scores, it shows that a CL-GD5428 is pretty close to what is the maximum framerate in DOS. At least for 320x200 mode. It is in windows that other cards can give a significant boost.

Graphic cards based on the CL-GD5428 are indeed fast, but their BIOS (optimization?), ram speed and manufacture quality also seems to be important too.
I own a CL-GD5424 based card that is slightly faster than a CL-GD5428 based one in DooM... Both using 1024 KB 80 NS.
Something funny is that a S3 805 is faster in pcp bench, 3dbench2 and in DooM (more than 3 fps gain on a dx2 66 😳 ) than a GD5428, but seems to run Hexen slightly slower. 🤣

I got some extra RAM, but made a mistake.
Being 1MB 30-Pin SIMMs, they can only be combined with 4MB 72-Pin SIMMs. They will not combine with the current 8MB modules, like I intented to do.
Half the 30-pin modules are 60ns, the rest are the usual 70ns.

Recently I got a motherboard I was not able to find much information about. Its model number is "MB455". After some research I figured out that this board is almost identical to the TK8498F / F4DXL-UC4 or PT-430. It is also pretty similar to the Biostar MB-1433 UIV. Assisted by some very informative images provided in this thread, I was able to add the originally missing voltage regulator components. With LT1584, R54=270 ohms and R55 = 150 ohms I get 3,5 V output voltage. R56 seems to be only important for an additional regulated voltage e.g. for some Cyrix models. I'm not able to clearly identify this resistor value in the given pictures though. gerwin, could you please post the value here?

Bios-wise I am now using an AMI Winbios designed for the PC Chips M912. A big advantage is that you can use EDO memory.