2 layers229.9 × 93.3 mm
2 layers229.9 × 83.8 mm
4b computer rev1
ethanjamesauto/modular_8bit_computer2- Size
- 229.9 × 83.8 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 35
- Nets
- 144
- Pads
- 306
- Tracks, vias
- 0, 2
- Routed
- Not yet
- KiCad
- KiCad 7 (file 20221018)
- Created
- 18 Aug 2024
- Updated
- 8 Nov 2025
Overview
4b computer rev1 is an open-source printed circuit board by ethanjamesauto, from the ethanjamesauto/modular_8bit_computer repository on GitHub. It is a 2-layer board of 229.9 × 83.8 mm with 35 parts on 144 nets.
It is built around the 74LS153DC, 74LS161DC and 74LS00SC, with the 74LS04PC, 74LS273PC and 74LS393P-E among its other parts. Its parts include 13 ICs, 8 connectors, 7 resistors and 7 diodes.
Main components
7
74LS153DC
PDIP-160℃~+70℃ 14ns 4.75V~5.25V 400uA 400uA 6.2mA 74LS Single Supply Tri-state output PDIP-16 Signal Switches, Multiplexers, Decoders ROHSTexas InstrumentsSignal Switches, Multiplexers, Decoders
74LS161DC
-0℃~+70℃ 14ns 32MHz 4 4.75V~5.25V 74LS 93mW Asynchronous Binary Counter Programmable divide ratio、Reset function、Cascade counter、Synchronous counting Rising Edge Synchronous - Counters, DividersTexas InstrumentsCounters, Dividers
74LS00SC
-0℃~+70℃ 15ns@5V,50pF 2 2.7V 2V 4 4.75V~5.25V 400uA 500mV 74LS 800mV 8mA NAND Gate - Logic Gates ROHSTexas InstrumentsLogic Gates
74LS04PC
PDIP-140℃~+70℃ 4.75V~5.25V 6 6.6mA 74LS PDIP-14 InvertersonsemiInverters
74LS273PC
PDIP-201 15ns 27mA 27ns@5V,15pF 30MHz 5ns 74LS Series 8 D-Type Reset Rising Edge PDIP-20 Flip Flops ROHSonsemiFlip Flops74LS393P-E
DIP-14-20℃~+75℃ 2 35MHz 4 4.75V~5.25V 400mW 40ns@5V,15pF 74LS Binary Counter Reset function DIP-14 Counters, Dividers ROHSRenesas ElectronicsCounters, Dividers
74LS85DC
CDIP-16-55℃~+125℃ 10mA 24ns Four channels TTL CDIP-16 Comparators ROHSTexas InstrumentsComparators
README
README.mdModular 8-bit Computer
This is the repository for an 8-bit computer system that is built using cards with a standardized interface.
- CPU card
- Protoboard card
- This card contains an onboard clock generator, address and data registers/buffers, and a protoboard area for testing designs.
- Bus interface modeling
Here's an example of a card:
Current Bus Specification
// The main bus wires (32+8=40 wires total)
// On the bus connector, all buses have LSBs closer to the power pins and MSBs farther away
wire VCC_5V;
wire GND;
wire clk; // generated by motherboard clock generator
wire rst_n; // probably a button on the motherboard
wire VCC_3V3;
wire we_n; // active LOW
wire oe_n; // active LOW
wire int_n; // pulled up by motherboard; driven down by any peripheral (could be used for interrupts)
wire [7:0] data;
wire [15:0] addr; // 64k address space is suppored by default. More address bits may be added later
wire [7:0] aux_bus;Parts
35| Qty | Value | Footprint | References |
|---|---|---|---|
| 7 | 470 | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | r1, r2, r3, r5, r6, r7, r8 |
| 4 | Conn_01x01_Pin | Connector_PinHeader_2.54mm:PinHeader_1x01_P2.54mm_Vertical | J4, J6, J7, J8 |
| 3 | 74LS153 | Package_DIP:DIP-16_W7.62mm | U3, U4, U8 |
| 2 | 74LS161 | Package_DIP:DIP-16_W7.62mm | U10, U11 |
| 2 | Conn_01x03_Pin | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical | J2, J5 |
| 1 | 28C256 | Package_DIP:DIP-28_W15.24mm | U1 |
| 1 | 3V3_RAW | LED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D7 |
| 1 | 5V | LED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D6 |
| 1 | 74LS00 | Package_DIP:DIP-14_W7.62mm | U7 |
| 1 | 74LS04 | Package_DIP:DIP-14_W7.62mm | U13 |
| 1 | 74LS273 | Package_DIP:DIP-20_W7.62mm | U9 |
| 1 | 74LS283 | Package_DIP:DIP-16_W7.62mm | U5 |
| 1 | 74LS393 | Package_DIP:DIP-16_W7.62mm | U12 |
| 1 | 74LS85 | Package_DIP:DIP-16_W7.62mm | U6 |
| 1 | CLK | LED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D5 |
| 1 | Conn_01x08_Pin | Connector_PinHeader_2.54mm:PinHeader_1x08_P2.54mm_Vertical | J3 |
| 1 | Conn_01x40_Pin | Connector_PinHeader_2.54mm:PinHeader_1x40_P2.54mm_Horizontal | J1 |
| 1 | Ext0 | LED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D2 |
| 1 | Ext1 | LED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D1 |
| 1 | Ext2 | LED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D3 |
| 1 | RESET | LED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D8 |
| 1 | ~ | Package_DIP:DIP-16_W7.62mm | U2 |
Questions
How big is the 4b computer rev1 PCB?
It measures 229.9 × 83.8 mm and has 2 copper layers, 1.6 mm thick.
What parts does the 4b computer rev1 use?
35 parts, built around the 74LS153DC, 74LS161DC, 74LS00SC and 74LS04PC. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the 4b computer rev1 KiCad files?
From the ethanjamesauto/modular_8bit_computer repository on GitHub, at the commit this page was made from: the board is smaller_4b_computer/4b_computer_rev1/4b_computer_rev1.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the 4b computer rev1 design in my own project?
Its repository states no licence, so its author keeps all rights: ask ethanjamesauto before reusing the design.
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