On Thursday 14 November 2019 13:05:06 Dennis Lee Bieber wrote: > On Thu, 14 Nov 2019 09:31:34 +0100, "R.Wieser" <address@not.available> > > declaimed the following: > >What I tried to indicate is that the Pi has 500,000 cycles to work > > with between two of those time events. I consider that to be quite > > a few. > > But the ARM instruction set is not a 1:1 with clock cycles. Loading > the program counter (in effect, jumps and subroutine calls) takes 5 > cycles on an older ARM 9 core. ARM apparently no longer provides > instruction cycle data for processors (and suggests one should use > performance counters to profile sections of code). > > And then one needs to take into account that Python is a byte-code > interpreted language, wherein an instruction may invoke whole > subroutines of native code. > > The R-Pi has never, to my knowledge, been billed as suitable for > industrial/real-time/process-control... It was billed as a device for > learning -- using Python and simple digital GPIO. The newer ones are > getting closer to serving as a general desktop computer. > Gee I hate to burst your bubble Dennis, but I am currently running a cnc'd, 70 yo, 1500 lb, Sheldon 11x54 lathe with a 2GB rpi4. And if it wasn't for the cost of changing the interfaces, I am considering replacing all my intel stuff running 3 more such machines, with rpi4's. The pi's all use an spi interface running at several tens of megabites a second, where the wintels are using some variation of the old parport at about 5 mb/sec. I think its called progress. But at 85 the grim reaper has come calling twice, and blinked twice. I'll get a new aortic valve in December, which should lengthen my visit here, but who knows for sure? > > > -- > Wulfraed Dennis Lee Bieber AF6VN > wlfr...@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/
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