BOM (Bill of Materials)
A complete list of components included in the rosco_m68k kit, along with introductory data on markings and polarity.
⚠️ IMPORTANT: Polarity
Some components in this kit are polarized. This means they can only be installed in a specific orientation. Incorrect installation may prevent the computer from booting. In the worst case — the component may burn out due to a short circuit or damage other parts of the board.
Component Table
Below is a list of all components. I recommend checking for the presence of all components before starting assembly.
| Component | Qty | PCB Positions |
|---|---|---|
| Ceramic Capacitor 100nF | 22 | C3,C4,C5,C6,C7,C8,C9,C10,C12,C13,C20,C22,C23,C24,C25,C26,C27,C28,C29,C30,C31,C32 |
| Ceramic Capacitor 7pF | 2 | C1,C2 |
| Electrolytic Capacitor 100µF | 7 | C11,C14,C15,C16,C17,C18,C19 |
| Electrolytic Capacitor 470µF | 1 | C21 |
| Resistor 4.7kΩ | 12 | R3,R7,R8,R9,R10,R12,R15,R16,R17,R18,R31,R32 |
| Resistor 10kΩ | 2 | R11,R19 |
| Resistor 1.2kΩ | 1 | R21 |
| Resistor 330Ω | 4 | R1,R2,R13,R14 |
| Resistor 270Ω | 1 | R28 |
| Resistor 2.2kΩ | 1 | R27 |
| LED Green 5mm | 2 | LED1,LED3 |
| LED Red 5mm | 2 | LED2,LED4 |
| Crystal 3.68 MHz (HC49) | 1 | Q1 |
| Oscillator 10 MHz (DIP-8) | 1 | Q2 |
| CPU MC68010P10 (DIP64) | 1 | IC1 |
| PLD ATF22V10C (DIP24) | 4 | IC2,IC3,IC5,IC6 |
| DUART SCC68681 (PLCC44) | 1 | IC4 |
| Priority Encoder 74LS148 (DIP16) | 1 | IC7 |
| Timer 555N (DIP8) | 1 | IC15 |
| Flash ROM SST39SF040 (DIP32) | 2 | U1,U2 |
| SRAM AS6C4008 512KB (DIP32) | 2 | U3,U4 |
| DIP64 Socket | 1 | for IC1 |
| DIP24 Socket | 4 | for IC2,IC3,IC5,IC6 |
| PLCC44 Socket | 1 | for IC4 |
| DIP16 Socket | 1 | for IC7 |
| DIP8 Socket | 1 | for IC15 |
| DIP32 Socket | 4 | for U1,U2,U3,U4 |
| Jumpers (1x02) | 4 | JP1,JP2,JP3,JP4 |
| UART Header 1x06 | 2 | J1,J2 |
| Expansion Bus 2x32 | 1 | J3 |
| Connector 1x06 | 1 | J4 |
| Power Header 1x02 | 1 | J5 |
| Button | 1 | S1 |
Brief Component Overview
Let's look at the markings, polarity, and specifics of the components included in this kit.
Resistors
Resistors are passive components; they do not require an additional power source to operate.
- Function: They resist electric current, limiting its flow or dividing voltage. In our computer, they are used for current limiting (to prevent LEDs from burning out), line pull-ups, and setting logic levels.
- Polarity: None. Resistors can be inserted into the board in either direction.
How to determine the value?
The resistor value is coded with colored bands on the body.- Method 1 (Accurate): Use an online calculator.
- Method 2 (Quick): Take a photo of the resistor and ask ChatGPT or another LLM what the value is.
Capacitors
Capacitors, like resistors, are passive components, but they are capable of storing an electrical charge.
- Function: Power filtering (suppressing noise and voltage drops) and acting as a buffer (when a chip suddenly consumes current, the capacitor instantly provides it).
Two types of capacitors are used in the kit:
Ceramic Capacitors
- Appearance: Small, usually yellow or blue (marked 104 for 100nF).
- Polarity: None. Can be inserted in any direction.
- Purpose: Fast capacitors for filtering high-frequency noise.
Electrolytic Capacitors
- Appearance: Cylindrical shape.
- Polarity: Yes! This is critically important.
- How to identify the negative: There is a light strip (often with a minus sign) on the capacitor body — this is the negative contact. Also, typically the shorter leg is the negative.
Warning: If the polarity of an electrolytic capacitor is reversed, it may overheat and fail, often with a loud sound.
Chips
These are active components. Inside these packages are complex circuits containing thousands of transistors.
- Function: Processor, memory, logic, timers. Power is strictly required for them to operate.
- Polarity: Yes! Critically important.
- Incorrect installation of a chip will lead to a short circuit (VCC goes to GND). The chip will start heating up intensely and burn out instantly.
How to determine orientation? Polarity on chips is marked with a notch or a dot.
- Notch: Indicates the front of the chip. A matching notch is also drawn on the PCB (and on the socket). They must be aligned.
- Dot: Indicates pin 1.
