Gerwin, you are a life saver! Last week I scored an 486 system on Ebay. The motherboard simply stated MB456V1.1 which gave no google results. Then I searched the UMC chip set and hit the jackpot with this post. Your package for TK8498F motherboard and VGA+Multi-I/O gave me all the info I was looking for. It seems this UCM motherboard design is available with a variety of different markings on the board. As already mentioned in this post, my 486 UCM rig also includes the UM85C418 VGA/Multi-IO VLB board. Thanks a million for your detailed posts, it has become my 486-bible.

Good to hear that this topic was helpful for you. I suppose quite a few typical 486 problems and solutions were encountered during the tweaking of this 486. Makes me wonder, which problem did I miss out on. Well... Fake cache for example 😉.

If you have time, please share some more details and/or photos of the system you obtained. I wonder what the CPU it came with, and wheter or not the VRM is present. Also, are you planning to use it as it is, or do you want to upgrade parts of it?

Yesterday I slightly updated the package on vogonsdrivers: Corrected typos in the CPU jumper table, Put the right jumper setting for 20MHz FSB in the layout and removed the duplicate VGA manual.

The 486 was extremely dusty. I did not take any pictures when it came in. I bought it because I needed the VLB video card, controller card and audio for another board. After I found this post, I played with the MB for a while, trying out some combinations of RAM, CPU and cards. In the end I put it aside due to its multiplier limitation. It came originally with an Intel 486DX2-66 S (heatsink glued to the CPU) but in the end I used an AMD 80486DX2-80. If found one lying around but, it too, had the heatsink glued. Since AMD does not mark the bottom for these CPU's I pried loose the heatsink but it took some of the top surface with it. With the help of cpu-collection.de I figured it was an AMD A80486DX2-80NV8T.

Here is the motherboard with the original 486DX-2 66-S. I had already removed the 2x8Mb EDO and replaced it with double sided 2x32Mb EDO. Cache shows all banks 32Kx8 20Ns for a total of 256Kb.

Backside of the CPU

Board marking

TK85C418GVIO-4J-D08 for which I found the jumper settings in your documentation! I disabled the HDD/FDC as it was not stable and used a seperate VLB I/O card.
This card ended up on the other 486 board (ZIDA 4DVS, AMD486DX4-100)

The Cirrus Logic GD5422 I used for the benchmarking

Continued:
The I/O board used for the benchmarks. It's an UMC card with UM82C863F/UM82C865F and branded MIO-VL P103.

The Crystal CX4235-XQ3 that also ended up on the new board. I was unable to get it working in pure DOS. No issues with WIN95.

The AM486DX2-80 after I removed the heatsink. It's the AMD A80486DX2-80NV8T as it has the 'N' is barely visible under X. In addition it shows the 'B' under A80, which is part of the B 9520 APD T marking.

AWARD BIOS

Excellent jumper markings on the board

Continued:

Test setup: I used an ATX power supply with the ATX-to-AT connector, a CF card for DOS 6.22 and benchmark programs, the AT-to-PS2 Keyboard adapter and a passive heatsink on the AMD486DX2-80.

VOGONS has an awesome collection of benchmark programs. A big Thank You to Phil and others for initiating and uploading these. As I am rather lazy than tired, I simply use Phil's DOSBENCH which I downloaded from his site.

Results:

Although the battery clearly needs replacement, it doesn't leak and after a couple of hours of operation seems to gather enough energy to retain changes in the BIOS for a couple of days. So, if I use the board regulary, there is no need to setup the BIOS each time I start the machine. It's a fun board and I am happy to have it in my collection.

Forgot: as can be seen above, I was playing with Write Back and Write Through. Speedsys 4.78 above shows the WT results. With WB the outcome for Speedsys is slightly higher. In the Excel overview different outcomes show and not all results are higher for WB.

Speedsys for WB

After tweaking the BIOS a bit more, all WB totals got even better.

Speedsys for WB after BIOS tweak.

Thanks for sharing these good photos and the background story!
Funny that it came with EDO SIMMS instead of FPM.
The Crystal CX4235-XQ3 card should work fine in DOS. Like with this set of Drivers. But this particular CS chipset has malfunctioning FM music, or so I was told.
I actually gave up on Write-Back cache. It was unreliable and also 'Anonymous coward' mentioned that WB does not work properly with VLB in general.

Two questions:
-What do you mean with "its multiplier limitation"?
-Did you use the original BIOS?, would it be possible to make a BIN file of the BIOS?

how do you install a intel dx4 1000 on this board TK 8498F ?

the manual does not say anything about dx4

I used the settings from Total Hardware '99 for the identical board F4DXL-UC4. All is in the package I uploaded to vogonsdrivers before.

1CPU Type     JP11         JP12         JP13     JP17     JP18     JP19     JP20
2AM486DX4     2-3          2-3          1-2,3-4  1-2,3-4  1-2      Open     Open

Note that the above does not match the silkscreened settings for P24C, which is the DX4 codename.

gerwin wrote:

I actually gave up on Write-Back cache. It was unreliable and also 'Anonymous coward' mentioned that WB does not work properly with VLB in general.

WB seems to work with the Asus VL/I-486SV2GX4 and the Am5x86-133 when the BIOS is updated.

I also noted that the mod with 3V CR2032 doesn't always work well with time counting when connected to the EXT BATT jumper header. This is because this jumper header usually goes through two series diodes (~1.5 V drop) before reaching the RTC when compared to the rechargeable solder point. Even if you disconnect the positive "charging" lead to the rechargeable battery and connect the CR2032 holder, it doesn't always keep good time after many months. So what I have started doing is using a double-stacked CR2032 battery holder and connect this to the EXT BATT header. Many EXT BATT headers request 6 V as noted in the manuals. I've had better luck with the double-stacked CR2032 holders. I recently ordered more from digikey.

I have the same board (without vrm), for the battery you can remove the R3 or CR4 (5v volts charging line) and you can use the lithium battery on pcb 😉

(I have yet to try)

Update: tested, work! 😀

I just got one of these boards - NOS it seems, no ISA slot scarring, no missing tin from around the mount screws, hell, it even smells unused.

BUT - it has the Dallas RTC - fortunately, the part I have to drill into is facing outwards at the very edge of the board, so no need to mess about with unsoldering it. It does POST but won't let me past the CMOS battery error.

What kind of board is it? (*edit NVM Jed118 usedRead, it was very effective.

Noyce, this board can take 3.45 v chips (mine has a different regulator but it's there) - I think I'm gonna throw my ITS 486ST 100 MHz or my 80 MHz DX2 from TI.

Wow that’s very slow for a 80Mhz 486