Laine Houghton wrote:
"Michael J. Mahon" <mjmahon@aol.com> wrote in message 2pednQOhY6CipL_fRVn-vA@comcast.com">news:2pednQOhY6CipL_fRVn-vA@comcast.com...Peter de Vroomen wrote: <snip>I still think 8 bit processors have their own right of existence. They aremuch easier to program the right way, because their instruction set is simple and to the point. But somebody should make an 8-bit processor with the speed of a few Ghz :).I agree. But since one of the major attractive characteristics of 8-bit processors is their deterministic execution times, it is very unlikely that speeds like this could be reached using current technology. Processor speeds over 100MHz invariably require pipelined execution (of a complex, not simple variety) and caches, which almost guarantee the loss of simple timing determinism. I suppose one could always put the machine into a "lockstep" mode when timing determinism was required, with every memory access treated as a cache miss and every conditional branch treated as a pipeline flush, but that would be _much_ slower. -michaelI haven't actually looked into them. But given what you've said above I'm wondering what a Real Time Operating System gets you. I can see the problems with preemptive multitasking. It would be interesting to look into the RTOS linux distribution for the specs.
Unfortunately, it doesn't get you microsecond accuracy. It would be quite difficult to write RWTS in a real-time OS environment. Even when interrupt latency is just a few microseconds, by the time you've executed a few dozen instructions, you could be off my many microseconds, depending on cache hits and misses. Of course, one could just stop depending on cycle-accurate instruction timings--but that wouldn't be an Apple II. -michael New Applesoft BASIC interface for NadaNet networking! Home page: http://members.aol.com/MJMahon/