The system features a modular design. Its basic version consists of:

Processor board

• 4004 or 4040 microprocessor
• RAM memory (2 x 320 bytes)
• ROM memory (system 256 bytes + user 2kB)
• Memory and I/O controller
• Reset circuit
• MOS/TTL interface circuit

Base board

• Power supply (5Vdc, 12Vdc, -12Vcd)
• 2 MCEXT expansion module connectors
• ROM memory (32kB – paged memory)

Enter board

• 24-key calculator keyboard
• Numeric LED display with integrated TTL circuitry (8 pieces of TIL311 or HP5082-7300)

Enter Controller board

• Keyboard and display control circuits

MC404 BUS board

• Integration of main system boards via MCBUS

Universal power supply from 16Vdc to 24Vdc (25W)

The solutions applied in the MC404 system enable full experimentation with historic 4-bit Intel processors. The processor board employs a 256-byte ROM memory (Intel 1702A) and 2kB memory for user programs (Intel 2716). In the 256B ROM memory, display and keyboard handling procedures are stored. Meanwhile, the 2kB ROM memory contains a fully functional, simple 8-character calculator. The 32kB ROM memory (EEPROM) on the base board allows for the placement and execution of user programs using system procedures or independently. The utilized MC404 BUS interface is fully compatible with the Intel MCS-4 system, enabling independent expansion of the system with additional modules. Moreover, the MC404 system has 2 MCEXT connectors for attaching various add-on modules (e.g., real-time clock, serial port, additional I/O circuits, etc.). To enhance the utilization of the MC404 system, an online toolset is available (emulator and assembler). These tools significantly reduce the startup time of custom applications.

MC404 is a meticulously designed computer system that serves as a showcase for the historical significance and technical prowess of the pioneering Intel 4004 and its successor, the 4040. Crafted with a modular architecture, the system comprises essential components, including a processor board housing the microprocessor (4004 or 4040), RAM and ROM memory units, memory control, and interface circuits. The base board integrates power supply and expansion capabilities, while the display and keyboard board offer a 24-key calculator keyboard and numeric LED display, seamlessly managed by dedicated control circuits. The MC404 system not only permits exploration of the legacy 4-bit Intel processors but also invites expansion through additional modules, facilitated by its versatile MC404 BUS interface. This system’s historical significance and practical utility are complemented by an online toolkit encompassing an emulator and assembler, enabling streamlined development of custom applications.