MicroCoreLabs
Veteran Member
- Joined
- Feb 12, 2016
- Messages
- 1,267
Introducing the MicroCore Labs MCL8080+
The MCL8080+ is an Intel 8080 emulator written in C which runs on the ATTiny85 microcontroller. Instead of the 40-pin package that Intel used the MCL8080+ local bus is implemented with a SPI serial bus with a number of optimizations!
The complete 8080 emulation and local bus are implemented in the ATTiny85 microcontroller and all of the system RAM, ROM, peripherals, and disk images are provided by a Teensy 4.0. Some resistor voltage dividers are used to convert the ATTiny85’s 5V IO’s to 3.3V for the Teensy 4.0.
The ATTiny85 is a very resource-limited microcontroller which has only 512 bytes of RAM, 8K of ROM, five GPIOs plus minimal serial bus support. The MCL8080+ 8080 emulation code was developed to save enough space to allow for a small 128-byte direct-mapped cache that greatly improved the performance by reducing activity over the SPI bus where all of the program code and data resides.
Due to these optimizations the MCL8080+ boots CP/M just a hint slower than a genuine Altair 8800.
The MCL8080+ is written in simplified C using a lot of inline code and minimal calls and returns to reduce space and execution time. The emulator passed all 8080 opcode tests including ZEXALL:
The MCL8080+ local bus is implemented using a custom SPI bus which is optimized to improve efficiency and speed. All accesses are performed in burst cycles with auto-incrementing addresses until there is an address change. The SPI chip select was converted to a toggle to indicate that there was a new address on the bus which saves the MCL8080+ from having to toggle it at the end of SPI cycles.
The SPI slave controller is supported by a Teensy 4.0 which implements a bit-banged custom SPI controller and provides 64KB of RAM, the floppy ROM bootloader, a UART interface, a floppy controller, multiple BASIC, ROM, and floppy disk images including CP/M.
Running all system RAM, ROM and peripherals over a serial bus would normally make the system too slow to be practical. The MCL8080+ achieves a massive speed improvement by using a 128-byte direct-mapped cache which eliminates unnecessary SPI bus reads for code loops and frequently used code.
The MCL8080+ can run the original Altair 8080 BASIC famously written by Bill Gates and friends.
And when running the Altair floppy bootloader ROM the MCL8080+ can access two emulated floppy drives to run CP/M, MBASIC, and a number of applications and games.
The project source can be found on GitHub:
github.com
The MCL8080+ is an Intel 8080 emulator written in C which runs on the ATTiny85 microcontroller. Instead of the 40-pin package that Intel used the MCL8080+ local bus is implemented with a SPI serial bus with a number of optimizations!
The complete 8080 emulation and local bus are implemented in the ATTiny85 microcontroller and all of the system RAM, ROM, peripherals, and disk images are provided by a Teensy 4.0. Some resistor voltage dividers are used to convert the ATTiny85’s 5V IO’s to 3.3V for the Teensy 4.0.
The ATTiny85 is a very resource-limited microcontroller which has only 512 bytes of RAM, 8K of ROM, five GPIOs plus minimal serial bus support. The MCL8080+ 8080 emulation code was developed to save enough space to allow for a small 128-byte direct-mapped cache that greatly improved the performance by reducing activity over the SPI bus where all of the program code and data resides.
Due to these optimizations the MCL8080+ boots CP/M just a hint slower than a genuine Altair 8800.
The MCL8080+ is written in simplified C using a lot of inline code and minimal calls and returns to reduce space and execution time. The emulator passed all 8080 opcode tests including ZEXALL:
The MCL8080+ local bus is implemented using a custom SPI bus which is optimized to improve efficiency and speed. All accesses are performed in burst cycles with auto-incrementing addresses until there is an address change. The SPI chip select was converted to a toggle to indicate that there was a new address on the bus which saves the MCL8080+ from having to toggle it at the end of SPI cycles.
The SPI slave controller is supported by a Teensy 4.0 which implements a bit-banged custom SPI controller and provides 64KB of RAM, the floppy ROM bootloader, a UART interface, a floppy controller, multiple BASIC, ROM, and floppy disk images including CP/M.
Running all system RAM, ROM and peripherals over a serial bus would normally make the system too slow to be practical. The MCL8080+ achieves a massive speed improvement by using a 128-byte direct-mapped cache which eliminates unnecessary SPI bus reads for code loops and frequently used code.
The MCL8080+ can run the original Altair 8080 BASIC famously written by Bill Gates and friends.
And when running the Altair floppy bootloader ROM the MCL8080+ can access two emulated floppy drives to run CP/M, MBASIC, and a number of applications and games.
The project source can be found on GitHub:
Projects/MCL8080+ at master · MicroCoreLabs/Projects
Ted Fried's MicroCore Labs Projects - FPGA CPU cores and emulators for the 8088, 8086, 8051, 6502, 68000, Z80, Risc-V, and also Typewriter and EPROM Emulator projects. MCL51, MCL64, MCL65, MCL...
github.com
Last edited:
I thought this would be an amusing addition since the Intel 8080 was an Altair-era CPU and the MCL8080+ can run Altair software. I felt that the people in the know would recognize that magazine cover...