Here's the BIOS from my only TACT8300 board. A text string inside reads:

Quadtel TACT83000/A38202/P29 386 BIOS Version 3.05.05
Copyright 1987-1990 Quadtel Corp. All Rights Reserved.

Thank you so much, QuickNick, for your prompt response. That's amazing! You cannot imagine how long I have search online for anything.

Looking forward to trying out this BIOS file on the SBC (photo attached). When researching online I was surprised how little information there is about 386 motherboards with that particular chipset, let alone this particular SBC. It should be the centre piece of my 386 build but got stuck as the BIOS that was on running on the board always gave be an error message (that there was an invalid Backplane ID) when booting into DOS.

So, thanks again. Hope this brings me forward. Will let you know how it worked out.

Nice boards...can you please post both BIOS also here?

Re: 80386 BIOS image collection

Let us know if you get the other BIOS running. If not, it may be easy to patch that error message out 😉

That 386 SBC has a really nice way of attaching the CMOS battery. Lugs to hold it in... so much better than soldering it in.

I've got a couple 386 SBCs myself but I think both have the battery soldered in and the one I am going to do a build with needs the battery replaced. But at least those Organic Lithium barrel batteries do not leak.

I'll make a better quality photo of the SBC (in the meantime I have added the co-processor) and put photo and BIOS file on the other thread.

I have tried the BIOS file that QuickNick sent me but it wouldn't post at all. Nothing.
Putting the original BIOS file back on I managed - as last time - to install DOS 5.0. But then, restarting the machine it simply doesn't boot into DOS but keeps on giving an error message (14) about an invalid backplane ID (FF). So strange, no settings in BIOS relating to Backplane identification.

I can't read/decipher these BIOS files but if anyone of you can and you find something that might be the cause for this error message, please let me know.

Also, something more a less unrelated. I don't get the market for these SBCs. Prices on Ebay for some of these 386 SBC are crazy. I'm not getting it. Why? Across the board they are going for USD 150 - 300. Are they still sought after by the industry?

So is this error message coming from DOS or from the BIOS?

If its from BIOS, why doesnt it appear when you install DOS for the 1st time? Or does it appear only when booting from hard disk and not from floppy?

I can take a look at the BIOS. Can you post a Screenshot of the error message?

Very helpful is also the POST-code that is displayed when the message appears and the ones before that. Hope you have a POST-card?
Otherwise its unnecessary hard work to find the position in the BIOS-code that needs to be patched.

In my opinion it's coming from the BIOS. I did get the same error message before the system booted from the first DOS 5.0 installation disk. I can actually boot from any bootable floppy disk (with the error message still showing up before and then booting from the floppy disk).
I'll send you the screen shots as soon as possible.
The exact error message reads: BIOS(14): Backplane ID incorrect.

to be more precise: BIOS(14): Backplane ID incorrect (FF)

When I open the BIN Bios File in Notepad you can actually find the error message line. Sorry, I guess that no big help.

Yes I see, its here

? ROM BIOS #18 Version 2.15
(c) Copyright International Computers Limited 1992

*** FOR TEST ONLY *** (920210)
%aMemory address error at %X0H
%aMemory address error at %x0000H

%d kB Base memory
%d kB Extended memory
%aMemory data error %XH

%aMemory parity error
%aBase memory size not correct %aExtended memory size not correct , updated
Keyboard locked, unlock and %aBIOS(15): Memory cache failure
%aBIOS(14): Backplane ID incorrect (%x)
%aBIOS(17): Serial port 1 failed
%aBIOS(18): Serial port 2 failed
%aBIOS(19): Parallel port failed

Press <F1> to continue or <Ins> for setup mode ?

Do you have a POST-card?

ehm...what is a POST-card?

.. No, I don't.

I checked on Ebay. They're not so expensive. So if I get one of these ISA/PCI combo POST-cards what shall I do with it? How does it work?

OK, execution of your BIOS starts at E05B

Offset of this error message is
0776: Backplane error

This value (and all other error strings) are used like...
mov ax, adress of message
call EAE9 (output message)

So the backplane error is displayed at cs:1741

The check is done at cs:1733 and cs:1737. If backplane is OK, execution jumps to cs:1747.

For fixing you need to replace every byte from cs:1733 to cs:1746 with "90". Thats a NOP, do nothing.

So search in your ROM for
74123cfd.....83c404
and replace with
90909090.....909090

But before you do that: Change one single byte in your ROM to see what happens. I assume a checksum error is displayed but I dont see the corresponding message. So at the beginning of the ROM exchange "Copyright" with "Cxpyright", write back and tell me what happens. That checksum check needs to be pacthed out, too.

For that you dont need a POST-card, thsi BIOS does not seem to output anything. But order it anyway, it important to have one 😉

Same check is done at CS:26D6 (without error message), so we need to pacth this as well.
But first we need to care about the ROM-checksum.

BlackLinus24 wrote on 2020-01-10, 19:48:

I have tried the BIOS file that QuickNick sent me but it wouldn't post at all. Nothing.

Bummer. That's unexpected. I've just checked my board moments ago, it's the same main chip as on yours, what differs is the cache controller. Austek on mine, i385 (I think) on yours.

Predator99 wrote:

Nice boards...can you please post both BIOS also here?

I will. This year, hopefully 😀
Got quite a few boards, I've dumped the BIOS from most of them, what I'm missing are good pictures of them.

Had a better idea, try this...

Wow...thanks!!!! I'm speechless. Thank you so much. I'll try it this weekend.
What about the Checksum. I haven't come around doing what you recommended. I was wondering if this can be done in Notepad as well or do I need to use a HEX editor?

I'm very excited in trying out the patched BIOS file. THANK YOU SO MUCH!!!!

No all done. You need a Hex-Editor, Notepad will not work. I didnt find the Code that checks the checksum so I changed another byte to make it match again.

Not sure if it works as I dont a have the board to test...if it does not I will try again. Tell me what happens and make some screenshots.

Thats fun and I am also learning while doing this 😉

OK. Got a time slot that allowed me to flash the patched BIOS and try it out. The error message does not appear anymore. However, it still doesn't boot into DOS and the blank screen with the letter j on the top left corner appears just as with the original BIOS. The error message about the Backplane would disappear leaving just a blank screen with the letter J. Also, the PC speaker beeped once.

Ok when looking at your Setup I dont think your Boot problem is related to this error message......

I also observed on my 286 with a 256MB CF-card that I was able to install DOS on it - but was not able to boot from it later. Also, most of the files on the CF were corrupted. You can verify this by booting from floppy and compare the files on HD and FD.

Solution: Install a network card with XT-IDE...this is also a work-around if the problem is really BIOS-related. The XT-IDE will be inititalized before the BIOS boots from HD...