Hardware Pinouts¶

Detailed connector pinouts and chip identification for the BC-250 board.

Source

This information is based on documentation from mothenjoyer69's bc250-documentation repository. Credit to mothenjoyer69, Segfault, neggles, and yeyus for the reverse engineering work.

Connector Overview¶

Connectors are listed clockwise from the M.2 header. Pin 1 is generally indicated on the PCB by a white silkscreen triangle (shown as > or ^ below).

Storage¶

M2_1¶

M-keyed M.2 slot supporting:

Two lanes of PCIe 2.0
SATA III connection

Jumpers¶

AUTO_PWRON1¶

> [ 1 2 3 ]

Jumper Position	Behavior
Pins 1-2	Auto power-on when 12V applied (default)
Pins 2-3	Wait for power button press

CLRCMOS1¶

> [ 1 2 3 ]

Jumper Position	Behavior
Pins 1-2	Power CMOS from CR2032 battery (default)
Pins 2-3	Clear CMOS settings

I2C and Debug Headers¶

I2C_HEADER1¶

> [ SCL SDA GND ]

The SCL pin is on the "lower" side of the board, closer to the power connectors.

This exposes an I2C interface which hosts PMBUS communications to the Intersil PMICs.

TPMS1 (LPC Header)¶

18-pin 2.0mm pitch header for boot-time monitoring:

 PCICLK -- [  1   2 ] -- GND
  FRAME -- [  3   4 ] -- SMB_CLK_MAIN
PCIRST# -- [  5   6 ] -- SMB_DATA_MAIN
   LAD3 -- [  7   8 ] -- LAD2
     3V -- [  9  10 ] -- LAD1
   LAD0 -- [ 11  12 ] -- GND
           [     14 ] -- S_PWRDWN#
   3VSB -- [ 15  16 ] -- SERIRQ#
    GND -- [ 17  18 ] -- GND

LPC is clocked relative to PCICLK at 33MHz.

Minimal connections for LPC monitoring:

  [ GND    -     - LAD2 LAD1 -    - - - ]
> [ PCICLK FRAME - LAD3 -    LAD0   - - ]

J2 (JTAG Debug)¶

Unpopulated 20-pin 1.27mm pitch footprint on the bottom of the board. This is an AMD HDT+ debug connector for JTAG debugging.

 VDDIO -- [  1   2 ] -- TCK
   GND -- [  3   4 ] -- TMS
   GND -- [  5   6 ] -- TDI
   GND -- [  7   8 ] -- TDO
TRST_L -- [  9  10 ] -- PWROK_BUF
DBRDY3 -- [ 11  12 ] -- RESET_L
DBRDY2 -- [ 13  14 ] -- DBRDY0
DBRDY1 -- [ 15  16 ] -- DBREQ_L
   GND -- [ 17  18 ] -- TEST19
 VDDIO -- [ 19  20 ] -- TEST18

Note: Pins TEST18, TEST19, DBRDY0 are left floating on this PCB.

Fan Headers¶

CPU_FAN1¶

Standard 4-pin PWM-capable fan header:

[ PWM Tach 12V GND ]
                ^

J4003 (Multi-Fan Header)¶

2.54mm-pitch connector for controlling five 80mm fans (designed for rack chassis):

[ GND F1T F2T F3T F4T F5T DET     ]
[ GND F1P F2P F3P F4P F5P GND GND ]
   ^

Pin	Purpose
`F1T`	Fan 1 (`CPU_FAN1`) Tachometer signal
`F1P`	Fan 1 PWM control input
`FnT`	Fan `n` Tachometer
`FnP`	Fan `n` PWM control
`DET`	Grounded if connected to power distribution board
`GND`	Ground

Fan 1 signals correspond to CPU_FAN1 tachometer and PWM pins.

Fan Numbering (BIOS vs Linux):

BIOS Fan	Linux Fan (NCT6686)
1	2
2	3
3	4
4	5
5	1

Power Connectors¶

Power Supply Control¶

No Native ATX Power Control

The BC-250 does not include native ATX 24-pin or PS_ON control circuitry. Standard ATX power supplies require manual activation.

Manual PS_ON Control¶

To use a standard ATX PSU, you must manually bridge the PS_ON signal (green wire, typically pin 16 on 24-pin ATX) to ground (black wire). This can be accomplished with:

A momentary push button
A latching button
A relay circuit

Without this bridge, the PSU will not power on.

PSU Fan Control Issue¶

Standard ATX PSUs without motherboard control will run fans at 100% speed continuously because the BC-250 cannot provide tachometer feedback. Solutions include:

Use a PSU with dedicated control board (e.g., relay circuit tied to 3.3V or 12V rail)
Accept full-speed fan operation

Recommended BIOS Setting: Set AUTO_PWRON1 to pins 1-2 (auto power-on) when using any external PSU control solution.

TPMS1 3.3V Power Rail¶

The 3.3V pin on TPMS1 (pin 9) is active only when the board is powered on, making it suitable for relay or control circuit applications that need to detect system power state.

J1000 (PCIe 8-pin)¶

Standard 8-pin PCIe power connector:

[ GND GND GND GND ]
[ GND 12V 12V 12V ]

Recommended wire gauge: 16AWG minimum for reliable power delivery.

Current capacity: Each MiniFit Jr contact can handle 9A (up to 13A for industrial-grade contacts). With three 12V pins, this connector can safely supply up to 324W (9A × 3 × 12V), or up to 468W with industrial-grade contacts.

For overclocking or high-power applications, consider supplementing J1000 with power from J2000/J2001 or soldering directly to the board.

J2000 and J2001¶

Alternative power connectors compatible with Molex Micro-Fit BMI 444280801:

        J2000                J2001
   v                     v
[ LED1 12V 12V 12V ]  [ 12V 12V 12V PGD ]
[ LED2 GND GND GND ]  [ GND GND GND GND ]

Pin	Purpose
`PGD`	`PGOOD` - 5V when PSU2 connected to rack chassis
`LED1`	Active-low LED output - mirrors green backplane LED
`LED2`	Active-low LED output - mirrors red backplane LED

Use both J2000 and J2001 for redundancy when powering from these connectors.

SPI Flash Header¶

J4004¶

2.54mm header for reflashing the BIOS SPI flash chip:

[ GND SCLK MOSI UNK ]
[ VCC  CS  MISO     ]
   ^

Pin	Function
VCC	3.3V
GND	Ground
CS	Chip Select
SCLK	Serial Clock
MOSI	Master Out, Slave In
MISO	Master In, Slave Out
UNK	Unknown (tied to ground via 10kOhm resistor)

Auxiliary Chip Identification¶

#	Designator	Chip	Description
1	`M2U2`	NXP CBTL04083B	2:1 PCIe x4 Multiplexer
2	`PUIO1`	Intersil ISL95712	Core supply PMIC
3	`PUA11`, etc	Intersil ISL99360	Smart Power Stage (phase controller)
4	`PUA1`	Intersil ISL69247	Main PMIC
5	`U30`	Realtek RTL8111H	Ethernet NIC (PCIe x1)
6	`BIOS_A1`	Winbond 25Q128JVSQ	16MiB SPI flash (BIOS)
7	`SU1`	AMD 218-0844029	A68H Bolton-D2H FCH chipset
8	`UIO1`	Nuvoton NCT6686D	SuperIO controller
9	`SIO1_R`	Macronix MX25L4006E	512KiB SPI flash (SuperIO program)

Two Flash Chips

The board has two SPI flash chips. When flashing BIOS:

Target: BIOS_A1 (16MB) - Winbond or Macronix
Avoid: SIO1_R (512KB) - Flashing this will brick the SuperIO controller