Re: [TUHS] Harvard and Von Neumann Architectures and Unix

This was the only way we could handle four 9600 baud serial connections on a 5.5Mhz 68000 processor. Back then the UART we used only buffered one character (also the case with the old 16450) - so one interrupt per char. And we "discovered" devices at runtime. So Yost wrote some code to hook up customized interrupt handlers that stuffed a larger char buffer specific to each UART. Essentially "partially evaluated" interrupt handler code to minimize memory accesses. A separate s/w interrupt was used to service the larger buffers. This was done at boot time but another instance of self-modifying code (that is not a virus) at runtime was by the old gcc compiler - don't know what it does now - but pointer to a GNU C's lexically nested function was actually a piece of code that was constructed at runtime with hardwired static link in it (recall that a nested function can reference variables from its lexical environment but normal C function pointers are represented as a single pointer).