bad news - that smaller socket is 99.9% 20-50% for PAL20 with custom logic programmed in. Even if you could identify and track down SCSI chip, most likely https://en.wikipedia.org/wiki/NCR_53C9x 53CF90 or 53C400, you wont be able to use it without the PAL most likely doing address decoding. It would require deep hardware knowledge to reverse engineer PAL equations.
Edit: looks like PALs are doing some memory mapped/IO conversion, and there should be three of them so maybe its not for that after all this PLCC28 socket might be just for SCSI BIOS SCSI BIOS for 53C400 based controllers

If you are really determined to get SCSI you will have to remove board from the case, make detailed high resolution photos and be ready to do some emasuements.

btw I thought that board looked familiar, and sure enough Iv seen it before when reading about NS32K UNIX 😀 http://www.cpu-ns32k.net/Opus.html

Hmm to me that picture does not look like the PCD-4L boards I have seen, looking at the back connector layout it does not look like this one: https://www.youtube.com/watch?v=CicFMfldmvE
Yes probably a PAL but could also be the bios for the scsi chip 😀

Horun wrote on 2024-02-10, 03:16:

Hmm to me that picture does not look like the PCD-4L
could also be the bios for the scsi chip 😀

yes im starting to lean in just a bios socket direction

https://archive.org/details/eu_BYTE-1993-11_O … /mode/2up?q=-4l

>SIEMENS NIXDORF GREEN PC
>Based on an Intel 25-MHz 486SL processor, the PCD-4L Green PC conserves power

maybe its called "PCD-4L Green PC". There we go https://www.kleinanzeigen.de/s-anzeige/siemen … 138749-228-2782 looks ordinary, but 25mhz 486SL and funny green sticker at the back about "for every Eko-PC a tree was planted" 😁

Ahh good one raz_pl. Agree easily be a NCR 90 or 400 series (or a Adaptec 6260 series ?), Are my eyes bad or is it 17x17 pin (aka 68 pin plcc ?
Both NCR 400 and 6260 did come in 68 pin..... just a thought.
Yeah near impossible to figure what scsi chip it could be...without some very deep digging (or a good picture with a chip in it 😀 )
Great find on which computer it is !

added: based on your find am now leaning toward an adaptec scsi asic but cannot be a 6360 as it is 80 pin.....

More details

The curious thing is that you can activate SCSI in the bios and set the I/O address to 140 or 340.

Amd NIC onboard

Found the manual in my archive (DL'd from seimens archive in 2022) but only in German. A26361-D706-Z120-US is the English manual but not ever found.....
Not much help on the type of scsi controller.....but does talk about installing the chip and says"2 ... Active termination module for SCSI" for the little chip..
Attached

@Horun
That's a great find from your archive. I have been looking for the documents everywhere. Thank you very much.
Which CHIP do you think I should try first?
NCR or AIC? I can only find the AIC-6250.
Would be great to find the driver disks there is surely info which chip it is.
Another idea is in BIOS dump. Maybe can find the manufacturer ID there.

tt0ny wrote on 2024-02-10, 18:46:

@Horun That's a great find from your archive. I have been looking for the documents everywhere. Thank you very much. Which CHIP […]
Show full quote

@Horun
That's a great find from your archive. I have been looking for the documents everywhere. Thank you very much.
Which CHIP do you think I should try first?
NCR or AIC? I can only find the AIC-6250.
Would be great to find the driver disks there is surely info which chip it is.
Another idea is in BIOS dump. Maybe can find the manufacturer ID there.

yes ! bios dump will likely have scsi bios contained within indicating which brand of controller.

not if the smaller socket is for scsi bios chip
20240210_120129.jpg doesnt open for me 🙁
53CF90 https://bitsavers.org/components/ncr_symbios/ … Manual_1993.pdf This one requires external clock on pin 51 and only works with 25 or 40 MHz. I dont see those clocks on your board.
53C400 https://bitsavers.org/components/ncr_symbios/ … /NCR_53C400.pdf is pretty awesome, it plugs straight to ISA. Page 38 has chip and ISA pinout so it should be easy buzzing it out with a multimeter to check for a match. ISA A11 to PLCC socket pin 25 should be a good start.

rasz_pl wrote on 2024-02-10, 20:04:

not if the smaller socket is for scsi bios chip 20240210_120129.jpg doesnt open for me :( 53CF90 https://bitsavers.org/component […]
Show full quote

not if the smaller socket is for scsi bios chip
20240210_120129.jpg doesnt open for me 🙁
53CF90 https://bitsavers.org/components/ncr_symbios/ … Manual_1993.pdf This one requires external clock on pin 51 and only works with 25 or 40 MHz. I dont see those clocks on your board.
53C400 https://bitsavers.org/components/ncr_symbios/ … /NCR_53C400.pdf is pretty awesome, it plugs straight to ISA. Page 38 has chip and ISA pinout so it should be easy buzzing it out with a multimeter to check for a match. ISA A11 to PLCC socket pin 25 should be a good start.

According to the manual the smaller socket is for the scsi termination. I'm kinda baffled by it, but hey, if the manual says so.

Here is the bios dump.
Unfortunately I can't find anything. But I am also not sure if I am looking for the correct id.
NCR Microelectronic Products Vendor
ID is 1000h.
Adaptec 9005

Hope is works now

Ok the bios file has the WDC Video bios at the begin, and the Phoenix bios after. There is no scsi bios internal that I could find, so that "active term" chip mentioned is most likely a bios chip.
Only other explanation is (bios is scrambled/buried in the Phoenix) or if a NCR 400 and some term chip then it cannot be booted from...like for use with external cdrom.

added: compared to a diff 486 board with WDC video, Phoenix bios and AIC 6260 scsi: and the 4L ones BIOS does have a large 19k gap where the other board <16k scsi bios is.
So the bios could have integrated but is not. just looking ......

weedeewee wrote on 2024-02-10, 20:24:

According to the manual the smaller socket is for the scsi termination. I'm kinda baffled by it, but hey, if the manual says so.

oh wow, didnt know those existed https://www.digikey.com/en/products/detail/te … UC5601QP/381528

tt0ny wrote on 2024-02-10, 20:48:

Hope is works now

Yes, this one loads fine, while that previous one loads to a blank screen, weird.
I see RTC clock, 14.3 16 20 MHz generators. That 99% excludes 53CF90.

You can verify PLCC 28 socket with multimeter measuring connections to external SCSI connector pins https://mm.digikey.com/Volume0/opasdata/d2200 … ev_Jul_2009.pdf and to bigger PLCC68 socket. For example are all PLCC28 pins closest to rear of the computer connected together and to ground? Once you find few links we can start narrowing it down.

a quick measurement shows that one side of the GND is

tt0ny wrote on 2024-02-11, 12:12:

a quick measurement shows that one side of the GND is

That seems to align with the datasheet for the terminator.
The middle pin of the opposite side should be pin 1 and is labeled TERMPOWER, thus should connect to pin 26 ( maybe also 25) of the external scsi connector.

Question about the bios dump. How did you take it and was scsi enabled in the system bios when taking it ? (that last part can be neglected if it was a direct read from eeprom).

tt0ny wrote on 2024-02-11, 12:12:

a quick measurement shows that one side of the GND is

Makes it very likely to be a terminator socket. Now find ground pins on the bigger one, and pins that are common between two sockets.