Erik Christiansen wrote: >[snip] > >It's not necessarily the alternative that everyone would rush toward, I >think. A small card with ethernet, parallel I/O, and preferably RS485, >with floating point maths coprocessor, and a couple of PCI slots, is >still the holy grail, I think. If it's economical, basic, and flexible, >more of us can use it as the stone in stone soup. > > Economical and industrial PC don't belong in the same sentence. Darn!
I looked up the price of a much much lesser device, an AMD Elan SC520-based unit with no graphics, no usable I/O, no discernible slots, and not much else (I don't know what the standard memory is, but for those unfamiliar with the SC520, it's more or less a glorified 486). That unit was priced at $1082 (it's here: <http://www.saelig.com/miva/merchant.mvc?Screen=PROD&Product_Code=IP036&Category_Code=>). The ones with LCDs are likely in the $3000+ range. I looked at the specs for the panel PC style ones, and they all use the same chipsets as a consumer motherboard might. The main difference is that they (probably) won't change the design every 3-6 months without telling you. These systems are unlikely to have significantly better realtime performance than a random consumer PC. I've looked into embedded PCs quite a lot, and I have a couple of them here for various projects. I have one project that uses an embedded PC with Mesa FPGA card and some custom analog I/O cards. It works for the task, but that's after extensive effort in reducing latency. If graphics or network are used, latency spikes to 16000-ish. This is on a machine that has <2000 under normal operation (and often under 200 ns). The chipset is spectacularly bad at PCI data transfer, with PCI transfers only about 2-3x the speed of parallel port I/O (with the exception that the address cycle is "instantaneous", and I get 32 bits per transfer instead of 8). The point of all this text is to say that in my experience, industrial PCs are much more expensive, and rarely any better for RT, than consumer PCs. They have features that may make them better for some applications, but RT performance is not one of them. The few manufacturers that even mention RT are usually talking about milliseconds, not microseconds. Those that are talking about microseconds are also providing a certified, often proprietary, OS. Just my 2 cents. - Steve ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
