WheatSystem Is A Homebrew 8-Bit OS

[Esperantanaso] has long been involved in producing homebrew 8-bit computers. His various builds could all achieve different things, but he grew frustrated that applications written for one could not be easily run on another. He recently took a big leap forward in this area, though, cooking up his own 8-bit operating system called WheatSystem.

The work initially began with BreadSystem, which relied on applications existing in bytecode. This would then be run by the BreadSystem OS which would handle the requisite conversion to the machine code of the system it ran on. However, the work quickly got out of hand when it came to implementing advanced features like the file system and floating-point handling. BreadSystem was looking likely to be too heavy to run on lightweight 8-bit systems.

That led to the development of WheatSystem, which kept the bytecode runtime environment, unified heap, and a memory permission system from BreadSystem. Fancier features like granular memory permissioning, automatic garbage collection, and file system directories were dropped.

WheatSystem quickly became a basic and functional OS. To demonstrate it, [Esperantanaso] created WheatBox 55A1, a small homebrew computer based on the ATmega328. It readily runs simple applications like a prime number generator or a basic RPG.

Creating one’s own OS is no mean feat, even at the 8-bit level. We’ve seen it done before, and it never fails to impress.

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Java Byte Code, Ahead Of Time Compilers, And A TI-99

Java famously runs on billions of devices, including workstations, desktops, tablets, supercomputers, and jewelry. Yes, jewelry. Look it up. [Michael] realized Java¬†doesn’t run on Commodore 64s, TI-99s, and a whole bunch of other platforms. Not anymore.

Last year, [Michael] wrote Java Grinder, a Java byte-code compiler that compiles classes into assembly language instead of being part of a JVM. This effectively turns Java from a Just In Time compiled language to a normally compiled language, like C. He wrote this for the 6502/6510, the MSP430, and a Z80. The CPU in the TI-99/4A is a weird beast, though, and finally [Michael] turned this Java Grinder on that CPU, the TMS9900.

While most of the development was accomplished with the MESS emulator, [Michael] did manage to run Java on real hardware. His friend gave him a TI-99/4A a few years ago with a few cartridges. Cracking those cartridges open revealed one PCB that would hold an EEPROM. Writing his Java byte-code-derived assembly to a 28c64 EEPROM, he had a cartridge that would run compiled Java.

Right now, the demo is pretty simple with low-resolution graphics beeps and bloops of music, and generally not what you would expect from a TI/99. This is mostly due to the fact that the API for the TI-99 is extremely simple. You can check out the results of that programming endeavor below.

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