VOGONS


First post, by bjwil1991

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I am looking for a BIOS, jumper settings, and user manual for a MiTAC IH4077H motherboard.

Specs:

2x IDE ports (keyed for modern IDE cables)
Floppy port (keyed for modern floppy cables)
2x Serial port headers
Parallel port headers
4x SIMM-72 FPM/EDO sockets (Banks 0-3)
Socket 3
Supports 3.3V, 3.45V, 3.6V and 4V CPUs
FSB support: 25MHz, 33MHz, 40MHz, and 50MHz
2x VLB 32-bit slots
6x ISA 16-bit slots

It had a Ni-Cd battery on it, but I removed it due to the battery leakage causing corrosion. I then since removed a lot of corrosion and cleaned the contact points with contact cleaner and 320 grit sandpaper, along with vinegar to help rid some of the corrosion. The system has a UMC northbridge and southbridge chips and the northbridge has the keyboard controller integrated.

The northbridge is a UMC UM8498F. The board itself is close to the IH4077D, except the CPU socket is rotated 90 degrees, has 2 IDE ports, and the front panel header is labeled as J14 with marking for which one has the functionality (restart, turbo, turbo LED, key lock, and speaker). The other ones are located somewhere for the power LED and HDD LED, but I cannot find information about it.

Pictures of the board: https://imgur.com/a/6x76EzF

Discord: https://discord.gg/U5dJw7x
Systems from the Compaq Portable 1 to FX-8350
Twitch: https://twitch.tv/retropcuser

Reply 1 of 13, by Horun

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I tried but cannot find anything but dead links. The old Mitac website is archived at Archive.org but the page you need was not crawled.
this page has the jumpers according to www.peteweb.com.
http://www.mitacservice.com/visitor/fcabdl.asp?fid=23860557
https://web.archive.org/web/20021201140358/ht … isitor/main.asp
https://web.archive.org/web/20010411002358/ht … r/v_welcome.asp

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor.

Reply 4 of 13, by Chkcpu

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perhenden wrote on 2022-03-16, 19:53:

Hi perhenden,

Do you happen to have the Mitac IH4077H BIOS?
The copy at https://www.ultimateretro.net/en/motherboards/9583 is unusable. It contains only the upper 64KB half from Shadow RAM, but the complete ROM dump should be a 128KB BIOS. 😉

Thanks, Jan

CPU Identification utility
The Unofficial K6-2+ / K6-III+ page

Reply 5 of 13, by perhenden

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Yes, I'd be happy to help. I've got access to this motherboard. There is something to work out - romsavat.exe produces a 64KB dump, same as on UR. Another dump bios tool, dumpat, produces an 1MB file. Perhaps you're able to cut that file and extract the 128KB rom? See attachment. The first 64KB of the bios seems to read as empty.
Unfortunately, the bios chip on my board, a Micronix MX28F1000PC-15, when put in a TL866II-plus cannot be read. The Mitac board can read it, though.

Attachments

  • Filename
    DUMPAT.zip
    File size
    37.86 KiB
    Downloads
    9 downloads
    File comment
    dumpat output
    File license
    CC-BY-4.0

Reply 6 of 13, by Chkcpu

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Thanks for the DUMPAT output. A small improvement because the F-Segment of the BIOS seems to be a real copy from ROM and not from Shadow RAM anymore. Amazing that this old tool knows how to (temporarily) disable Shadow RAM on the UMC498 chipset!
But the DumpAT tool is obviously made for getting 286/386 and early 486 BIOSes and only produces a 64KB BIOS. The rest of the file is filled with FFh, so still no valid E-Segment.

Luckily we have DOS’s Debug tool and can do this the old fashioned way. 😉
I’ve made a Debug script named GETBIN.DEB, attached below, that copies both the F- and E-segment from memory (ROM or Shadow RAM). At the DOS prompt, run the command:

DEBUG < GETBIN.DEB

This produces 2 files, SEG-E.BIN and SEG-F.BIN that are 64KB each. With these files I should be able to construct the complete 128KB BIOS image.
Please send both files with your reply.

Jan

Attachments

  • Filename
    GETBIN.zip
    File size
    183 Bytes
    Downloads
    5 downloads
    File comment
    Debug script for copying 128KB BIOS
    File license
    Public domain

CPU Identification utility
The Unofficial K6-2+ / K6-III+ page

Reply 8 of 13, by Chkcpu

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Amazing, this is one coy BIOS, it keeps hiding itself!

The Debug copying went well indeed and I can see some BIOS code in the segment-E part now. However, only the top 8 KB of this segment is visible and the rest is still hidden. 🙁
The visible part contains the Interrupt 10h handler, the BIOS’s Video Display Services, which obviously should remain visible during run-time.

In the F-segment I see the call-table for all POST routines, which points to addresses in the E-segment. This means the hidden part of segment-E in this BIOS contains all POST routines. Essential code for a working BIOS copy, but only needed during POST so this BIOS hides this part at run-time…

I have an idea how to disable the shadow RAM of the E-segment (not possible via the BIOS Setup unfortunately) so the ROM code becomes visible. But I need some time to work that out.

Jan

CPU Identification utility
The Unofficial K6-2+ / K6-III+ page

Reply 9 of 13, by Chkcpu

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Hi perhenden,

Okay, this is what I like you to try.

In the attachment you’ll find the DOS-based CTCHIP34 chipset configuration tool with a .CFG file for the UMC498 chipset.
As CTCHIP34 originally doesn’t have support for the UMC498 chipset and the databook is nowhere to be found, I wrote this UMC498GP.CFG file by analyzing another UMC498 BIOS. This particular UMC498 BIOS is 64KB and therefore only occupies the F-segment. So it allows option ROMs in the E-segment and has BIOS Setup options for Enabling/Disabling Shadow RAM in this E0000h-EFFFFh memory region.
By following the BIOS code, I found the UMC498 chipset registers and bit-definitions that control Shadow RAM. For the E-segment, this appears to be reg 35h bits 7-2.

At the DOS-prompt on your IH4077H system, type the command:

CTCHIP34 UMC498GP /35

and you should see the actual reg 35h setting as programmed by the BIOS.
The bits are probably 010111xx to indicate an enabled and write protected Shadow RAM E-region. By entering the command:

CTCHIP34 UMC498GP /35:=%000000xx

You will disable Shadow RAM of the E0000h-EFFFFh memory region, allowing the BIOS ROM to be read directly from the EPROM.

Now run my Debug script again to copy the BIOS to the 2 SEG files.

Member feipoa was so kind to test the UMC498GP.CFG file on his PCChips M912 UMC498 board and this worked fine. So I’m confident this will work on your UMC board as well. 😀

Jan

Attachments

  • Filename
    UMC498GP.zip
    File size
    35.85 KiB
    Downloads
    4 downloads
    File comment
    CTCHIP34 + UMC498 config file
    File license
    Public domain

CPU Identification utility
The Unofficial K6-2+ / K6-III+ page

Reply 10 of 13, by perhenden

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Thanks! I tried it, but the resulting seg-e.bin unfortunately has empty (nothing but FFH) contents. I made sure to delete the old .bin files first.

DSC_1262.JPG
Filename
DSC_1262.JPG
File size
452.79 KiB
Views
168 views
File comment
First command output
File license
Public domain

I tried the variations
CTCHIP34 UMC498GP /35:=%000000
CTCHIP34 UMC498GP /35:=%00000000
CTCHIP34 UMC498GP /35:=%00000000xx
with no difference in the result

DSC_1263.JPG
Filename
DSC_1263.JPG
File size
564.63 KiB
Views
168 views
File comment
Second command output
File license
Public domain

Reply 11 of 13, by perhenden

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I gave the bios chip a third run in the TL866II programmer. By disabling BOTH pin detect and check id in the Xgpro software, I was able to read the chip (id reads as 0xC211, but should probably have been 0xC21A according to datasheet). I don't trust this chip, and I'm happy about replacing it.
Modbin could read it (checksum OK), and when the rom is written to a new chip, the motherboard posts and boots to DOS ok.
I don't know if the read is 100% good (depends on how the checksum is made/verified).

Filename
IH4077H_R102a.zip
File size
50.39 KiB
Downloads
7 downloads
File comment
IH4077H bios R1.02A
File license
Public domain

Reply 12 of 13, by Chkcpu

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Great that you were able to read the EPROM with your TL866II afterall. 😀
Yes, I agree that this chip was on its way out.

I've checked this new BIOS dump as well and it looks perfect. All code is where it should be and the various checksums are correct.
You can send this BIOS to ultimateretro, so they can replace the unusable one.

Thanks for trying my UMC498GP.CFG file. Good to see it works on this board, including changing that chipset register.
Too bad it didn't have the expected effect. 😉

Cheers, Jan

CPU Identification utility
The Unofficial K6-2+ / K6-III+ page