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Anyone ever see a CPU with this identification? Or does anyone know what kind of motherboard this is? Thanks

Photograph of a motherboard from the early 1990s, with one 8-bit ISA slot and six 16-bit slots, one of them occupied by an unidentifiable card (perpendicular to the board). The BIOS chips are labelled as Quadtel 386 and bear serial numbers 554185 (LO) and 554314 (HI). In the upper right corner there is a large chip labelled only as ‘DS39399.A 107M7NX’, next to an empty socket; presumably the CPU and the FPU socket. Next to the presumed CPU is a barely readable label ‘520-05211-04/F2 …’

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  • 1
    What is the printing on the Siemens chip in the upper-left? Unreadable in photo...
    – Brian H
    Commented Nov 23, 2021 at 20:11
  • Also, it looks like the board's part number is at the top-right but is obscured by the "①" printing (PN ….211-03?). Can you make out what is says?
    – Alex Hajnal
    Commented Nov 23, 2021 at 20:21
  • There's what appears to be a logo etched on the CPU (a blocky ':C` at the bottom-left corner) that looks familiar but I can't place it. Looks almost like the IChaus logo but I don't think it is Does anyone recognize it?
    – Alex Hajnal
    Commented Nov 23, 2021 at 20:48
  • Yes, the CPU is U1, and its a 386 but no idea beyond that. I find nothing when I search on its number, "DS39399.A" and "107M7NX" under that. Ive never seen any writing like this on a CPU. The Via chipset is an SL9030. The siemens chip is the onboard IO I think and its labeled SAB B2C250-N. CheckIT reports that its a 386DX at 25mhz but thats all I know. Would really like to find what the jumpers settings are but there is nothing on the board to indicate what the settings are.
    – Jeremy Hubbard
    Commented Nov 23, 2021 at 21:03
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    I've asked about a chip ID over on ee.se.
    – Alex Hajnal
    Commented Nov 23, 2021 at 23:25

3 Answers 3

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I inquired about the CPU over on ee.se. The chip appears to be an AMD Am386DX-25.

Compare the lower printed number (107M7NX and 107M7NZ), the fonts used, the logo at the bottom-right, and the laser-etched number (23936).

Unknown chip Am386DX-25
Unknown chip Am386DX-25
Alternative view

Source: computerbase.de via @SpehroPefhany's answer on ee.se

@njuffa has pointed out that the logo laser-etched at the lower-right is that of Kyocera, the manufacturer of the ceramic package.

Kyocera logo

Source: Kyocera

As for the board's part number I suspect it's on the white sticker at the top of the board (620-05211-04/F2 DR00-00022). The top copper layer has something similar etched on it at the top-right (P/N xxxxx5211-03 where xxxxx are obscured). That could imply that the board's base part number is 620-05211 with 03 and 04/F2 being the revision numbers for the top copper layer and the board as a whole, respectively. Unfortunately that part number doesn't show up online anywhere. More photos (especially of the bottom of the board) could be helpful.

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  • Sounds plausible. Great job.
    – Raffzahn
    Commented Nov 24, 2021 at 2:38
  • @Raffzahn I can't really take credit (someone else recognized the chip). Thought those markings looked familiar though...
    – Alex Hajnal
    Commented Nov 24, 2021 at 2:40
  • Seems like a rare chip, is it worth anything?
    – Jeremy Hubbard
    Commented Nov 24, 2021 at 2:43
  • @JeremyHubbard Not a clue.
    – Alex Hajnal
    Commented Nov 24, 2021 at 2:44
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Apart from the unrecognized branding on the CPU (ceramic; upper-right in photo) chip, this appears to be a bog standard ISA '386 motherboard, probably running at 25 MHz.

  • CPU looks like the right packaging for a 80386
  • Empty 80387 FPU socket
  • Quadtel "386" BIOS with appropriate late-80s Copyright
  • 50.0MHz oscillator adjacent to CPU; usually provided 2x the CPU clock
  • Typical VIA chipset

Of course, normal Intel or AMD branding on the CPU chip would make it obvious. I'd be concerned about the provenance of the CPU that is installed.

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  • I guess CPU is the big chip labelled U1 in the upper left corner, below the power connector.
    – Martin Maly
    Commented Nov 23, 2021 at 20:04
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    @MartinMaly CPU is upper-right in photo, ceramic, next to empty FPU socket.
    – Brian H
    Commented Nov 23, 2021 at 20:07
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    @MartinMaly Well, maybe. I can't read the printing on that upper-left chip. Maybe MB supports CPU upgrades.
    – Brian H
    Commented Nov 23, 2021 at 20:14
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    @BrianH It's a VIA FLEX I SL9X50 Memory Address Controller.
    – Raffzahn
    Commented Nov 23, 2021 at 21:58
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    U26 looks like the CPU, and U1 looks like keyboard controller.
    – Justme
    Commented Nov 24, 2021 at 11:04
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Going by pinout and socket type it's a pretty generic 80386DX (*1) board based on the VIA FLEX I chipset (SL90xx). Probably 1990/91ish.

It would need a better set of photos - especially of the backside to find some hint. Finding the correct type without further marking is next to impossible, as many did produce following the same layout.

*1 - Visible due the presence of two SL9020 Memory Data Controllers 'below' the CPU - a 386SX would only need a single SL9020.

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