TheRetroWeb has it.

Apart from retroweb, I did not find any confirmation that the ATC-6400 is the same board. The manual does not say anything about the JP11 connector and says that the board only supports Pentium II.
The board correctly recognizes the Pentium III Katmai 550. The Coppermine on modded PPGA adapter also works, but it does not start after changing the FSB from 66 to 100.

"ATC-6400" is even printed on the white sticker at the bottom.

Hope you replaced the leaky cap...

dulu wrote on 2024-07-21, 23:29:

Dual processor systems have always been outside of my scope of interest, so I didn't know much about xeon slot II processors. However, this mobo allows for a close comparison of xeon vs pentium processors in games under Win98, and theoretically creating a period-correct system that will outperform the highest PII / PIII models (without leaving the second slot unused). Since few people have such an opportunity, I feel obliged to create such a test : )

You write "Dual processor systems". I would not expect this board to run with both a PII AND a Xeon at the same time?

dulu wrote on 2024-07-21, 23:29:

2: What is the JP11 connector next to northbridge for?

That looks like a connector for a thermistor (for measuring cpu temp)

dulu wrote on 2024-07-22, 09:27:

Apart from retroweb, I did not find any confirmation that the ATC-6400 is the same board. The manual does not say anything about the JP11 connector and says that the board only supports Pentium II.
The board correctly recognizes the Pentium III Katmai 550. The Coppermine on modded PPGA adapter also works, but it does not start after changing the FSB from 66 to 100.

Run Bios Patcher on it, see if that helps.

majestyk wrote on 2024-07-22, 09:55:

"ATC-6400" is even printed on the white sticker at the bottom.

Hope you replaced the leaky cap...

You`re right, what a shame..
Cap replaced, like i siad 😀

H3nrik V! wrote on 2024-07-22, 10:39:

dulu wrote on 2024-07-21, 23:29:

Dual processor systems have always been outside of my scope of interest, so I didn't know much about xeon slot II processors. However, this mobo allows for a close comparison of xeon vs pentium processors in games under Win98, and theoretically creating a period-correct system that will outperform the highest PII / PIII models (without leaving the second slot unused). Since few people have such an opportunity, I feel obliged to create such a test : )

You write "Dual processor systems". I would not expect this board to run with both a PII AND a Xeon at the same time?

I meant that the board is designed to run a single Xeon, so it is better suited to a Win98-based system. I know that it won't support two processors at the same time 😀

These Freeway red PCBs are eye catching for sure.
Great for early P2 and P3 processors. Well packaged for that mission. But if you want more from them - they will struggle.
Here is a short overview of FW-6280BXDR, for reference. It answers some of your questions.
Usb mouse works in “later” windows/linux versions.
One issue with the 6280 version is the closely placed cpu slots. Prevents you from inserting a second CPU with standard height heatsink/fan. Requires finding low profile ones, which is more difficult nowadays than it sounds. Not great.
I think it is the same for your board, but since it does not allow dual cpu configuration - not a problem really.

The board model number "150" does not gurantee that it's 150 MHz.
There is no mention of "150MHz" or any other frequency in the text on the motherboard that directly corresponds to the model number "150".

FSB is controlled through the BIOS.
There are options for 150 and 155, at least in the 6280 model. They kind of work.
I assume it is similar for 6400.

kevin223 wrote on 2024-07-23, 14:40:

The board model number "150" does not gurantee that it's 150 MHz.
There is no mention of "150MHz" or any other frequency in the text on the motherboard that directly corresponds to the model number "150".

It's clearly listed on their spec sheet for the board...

I will start playing further only when I get the right xeon. After a long search, it seems that I will not find a matching retention bracket, no board has such a mounting. I'll have to create something.

In the meantime - does anyone know what board/graphics card this heatsink was mounted on? I remember well that it was on something that I moved to scrap. It must have been some riva tnt, i740, mx200 or something. I clearly remember that characteristic drilled hole in the corner.