So it all started with my neighbor gifting me his 386sx-20 NCR System 3120 Laptop. Unfortunately the floppy drive is broken and it is using an FPC 26-pin proprietary ribbon cable connection with an uncommon 1.25mm pitch to top it off. The drive is an EPSON SMD-1000. The laptop is not the main topic of this post, just for some background.

Right next to the laptop's floppy connector is an SPC2052F 80-pin smd floppy controller IC. I suspect it also contains some IDE functionality as it is also wired to the IDE connector. The IC seems to be a phantom, I could find zero information online except that it appears to have been made by EPSON.

As such rabbit holes go I found an ISA 16-bit IDE controller on eBay that was using the exact same IC and I ordered it from the UK. I traced its pins to the standard 34-pin floppy connector and I think I now have the correct mapping to be able to connect a standard drive to the laptop's 26-pin FPC. I've attached the pinout info I have so far. I assumed the leftmost pin on the bottom was pin 1 and then went counter clockwise.

I realize the ISA multi-IO card is not particularly exciting. But now that I have it here and come this far I wanted to properly research it for documentation purposes (Retro Web..). Again, I found no match online at the usual suspects. It says C837 on the back of the pcb, bottom right.

Does anyone have any information on the SPC2052F controller chip by (supposedly) EPSON and / or the controller card?

Concerning the controller card:

• JP1 connects VCC to GND through R2 and VCC to pin 24 of the SPC2052F. I suspect this enabled / disables the floppy but have not tested it.
• JP4 is wired to IDE pin 39. It connects pin 39 through a resistor to VCC. This has to be the activity LED connector.
• JP5: Pin 1 connects to VCC via R3. The middle pin connects to pin 13 of the PAL U5. Pin 3 connects to pin 72 of the SPC2052F. Pin 2-3 were shorted by default.
• JP6 is factory soldered with 2-3 shorted. Pin 1 is the same as JP5, so VCC through R3. Pin 2 connects to PAL U5 pin 11. Pin 3 connects to pin A11 (AEN / Address Enable) of the ISA bus.