ColdFire was Re: Performance-oriented development blah blah blah

On Oct 27, 2011, at 3:09 PM, Cameron Kaiser wrote: Well, you're using the past tense; they're still very much alive and well, though generally highly integrated as opposed to standalone processors. Some of the more modern ones have some nice additional MAC (multiply-accumulate) instructions with an extended-range accumulator for e.g. light DSP work. Unfortunately, those MAC instructions are all A-line instructions, so you can't use A-line words to force a trap to the illegal instruction handler (which is how the 68K Mac system did its toolbox calls). It's an "assembly-compatible" 68K variant, which means the opcodes have been shuffled around to optimize silicon area in the decoder, but all the mnemonics are still there aside from a few bits of functionality they decided were unnecessary or extremely seldom-used. Early Coldfires didn't have separate user and supervisor stack pointers like the real 68K, but modern ones all do and I never had to work with any without. It's not object-code compatible with the 68K, but reassembling generally does the trick and most of the SPRs are pretty much the same. It also certainly runs less power than the original parts. The newest Coldfire+ line is designed for super-low power operation, so it runs a handful of ?A at sleep and just a few mA (up to a few hundred, depending on how fast you run) in run mode. It's good for "semi-pro" hobbyist work, i.e. if you have a project that you like enough to make a proper PCB and get it professionally assembled (unless you're just that good at putting on BGAs, which is at least possible with a heat gun), but I honestly think it's a lot easier to get good mileage out of an ARM, especially with cheap open-source dev tools. - Dave