Hadn't heard of it but worked up a search anyhow:

This DFI EB3486-TN motherboard manual mentions the TACT84544 (but none of the others): http://www.elhvb.com/mobokive/Archive/Dfi/man … tn/eb3486tn.pdf
... ie. MB 486 DIAMOND FLOWER, REV A, W CPU MODULE EN4DCW-25/33 REV0 https://www.newegg.com/Product/Product.aspx?I … =9SIAB5A6CR9148
Looks like the photo on Newegg has the chipset!

These are probably all worth checking into: https://www.google.com/search?q=80486SX+%22Ch … fe=off&filter=0

Otherwise seems to come up as a chipset in certain model Unisys 486 complete server systems and workstations:
Which don't exactly run Windows AFAIK.
https://groups.google.com/forum/#!search/tact … -place=overview
Unisys 6000 DT/2
Unisys 6000 DT/3
Unisys MPE 56081
Unisys MPE4333E
and others
https://groups.google.com/d/msg/comp.sys.unis … U4/p-mzHLzOWhUJ
https://groups.google.com/d/msg/comp.sys.unis … bA/jiQhammplLEJ

Beware, the DT2/3 like the U6000/100/300 and their associated PC models, were based upon a horrid TI TACT 84500 EISA chipset. The chipset was pretty buggy, and ... well you know the rest. If you are porting an O/S to it, TI did do a developers guide to the TACT 84500 chipset, it may be worth investigating. However, the boards do have many additional configuration registers which override the TI mapped registers.

...

For your search, the MPE56081 was also sold as the U6000/300. The 486 version was sold as the U6000/100. They all used the same […]
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For your search, the MPE56081 was also sold as the U6000/300. The 486 version was sold as the U6000/100. They all used the same basic ECU/SCU programs (.EXE files), but with differing config .CFG files. The .OVL files MAY be the same but I doubt it. I used to configure my U6000/300 (and U6000/500 Model 20 - the dual CPU version of the U6000/300) with a U6000/35 ECU/SCU software set, I just used the new .CFG and .OVL files.
...
Now, word to the wise, these systems were based upon a very buggy EISA chipset from TI, the TACT84500. Also, the system motherboard, the
processor board and evene the memoy board had all kinds of latent bugs in them. The systems have a notorious habit of hanging and crashing. One particular trouble maker is the CPU board to motherboad connectors. Make sure everything is screwed down real tight.

Also seems to have been used in some PA-RISC systems (non-Intel as far as I know) but beats me which, there's a list of models that could have here:
https://www.openpa.net/pa-risc_chipsets_lasi.html

There's some sort of 1 page article about it at Heise, pay 0.99 Euro to read it (IIRC they take Paypal): https://shop.heise.de/katalog/eisa-chipsatz-v … xas-instruments

Various patents mentioned the documentation Texas Instruments published for the chipset, they are as follows:
- Texas Instruments, TACT84500 EISA Chip Set, Designer's Handbook, 1991
- Texas Instruments, TACT84500 EISA Chip Set User's Guide, 1991
- Texas Instruments Corp., TACT84500 EISA Chip Set, Preview Bulletin, 1991
For a time, you could request out-of-print manuals from them (and they'd send it via fax or email) but I believe those days are probably long past. Never hurts to try, though. Otherwise maybe eventually Bitsavers will get their hands on documentation, but it might take another decade or two.

This guy mentioned the chipset in his online resume and perhaps could tell you about the chipset if you ask: https://www.linkedin.com/in/pete-nelsen-0867a55/

What brings up this direction of research, idle curiosity? 😀

Amazing! Thank you so much for the effort and time you spent while looking up that information! Prior creating this thread, I had already seen most of the info you have provided here, except for the actual computer systems, that used TACT84500 chipset.

Now, word to the wise, these systems were based upon a very buggy EISA chipset from TI, the TACT84500.

Sigh, if it was that bad, then no wonders why it is so unknown and undocumented.

This guy mentioned the chipset in his online resume and perhaps could tell you about the chipset if you ask: https://www.linkedin.com/in/pete-nelsen-0867a55/

Peter Nelsen was responsible for mentioned chipsets datasheet generation. I have no doubt that he would be able to tell about it quite alot, but I woudn't dare to bother him over it 😀

Now I've spent whole evening trying to find EB3486-TNs AMI BIOS, browsed google and wayback machine (dfi.com/dfiusa.com/dfi.com.tw/FTPs, etc.) for few hours, but couldn't find its BIOS image. Information about Unisys workstations was even more scarce.

Stiletto wrote:

What brings up this direction of research, idle curiosity? 😀

I'm trying to find a BIOS image of absolutely ANY motherboard that used full TI TACT84500 chipset, so that I could test/revive my AST Premmia 486 motherboard that I received stripped down, BIOS chip included. I was able to find a BIOS update diskette for it here 05508313.exe, but *.IMG file there has only main BIOS in it. AST bioses at that time consisted of two parts: compressed main BIOS (system BIOS + integrated graphics card BIOS) and a "Flash loader" (or a bootblock) which was used to initialize chipset and decompress main BIOS. I think that Flash loader part was never provided by AST support, which leaves me no other choice, but to look for alternatives.

I see.

Shit, given the rarity, I'd probably just drop the cash on the DFI board on Newegg and be done with it. Unfortunately, that's fairly pricey. Could try a last-ditch effort to contact DFI before that tho.

I'd also try asking over at VCFED for any clues if I were you.

332 bucks for a 486 AT motherboard... What are they thinking!? I'm not that desperate.

On a spare time, I'll filter out all motherboards that could potentially use TI TACT chipset by the help of TH99. If I won't find a single BIOS image from the MB list, I'll try to seek help elsewhere.

I find it difficult to believe that I'm the only one at Vogons who has a MB based on TI TACT84500 chipset.

Well, 4 big chips as part of the chipset seems to lean towards more server/workstation-class motherboards, and the Google results seem to agree... and while there's a few, there's not a TON of server motherboard collectors here at VOGONS. I could be way off base though.

The TH99 angle sounds like a good bet. Good luck!