C
Curt Wuollet
That last statement, Sir, is absurd. If you look at the throughput of a typical PLC class processor VS typical PC processors you'll begin to grasp where the problem is. It takes an almost inconcievable amount of bloat and cruft to slow a PC class processor to the point that it can't scan 10 times the IO, 10 times faster than most PLCs. And only running the World's _least_ reliable software makes the
reliability argument credible, in my _real world_ experience. Indeed, a typical PC processor with reasonably efficient software could easily saturate any automation backplane I've seen and nearly any network designed for automation as well. Indeed, if you were to port the PLC software directly to a PC, which is probably quite doable since many PLCs run x86 engines these days,
all your perceptions of PC speed and efficiency would be blown out of the water. The reliability would amaze you as well.
My point is: If you tried to run the equivalent of Windows on your PLC, it would then be both extremely slow and extremely unreliable. But that is not a problem with the hardware. A typical PC with rotating disks and fans might give away 60% of the mtbf of a PLC. More in a really bad
environment. But without those, the two should be much closer as the electronics aren't as different as they are similar.
The other 99% of the "failures" come from simply running the default software rather than making an intelligent selection _for_ reliability. That's why the telcos and most ISPs and financial exchanges and the massively parallel supercomputer folks don't run Windows. They choose software for reliability.
In other words, if your PC is slower and much less reliable than your PLCs, you have a dire need for different software. But don't blame the PC. Borrow a Tivo and do the math :^)
Regards
cww
reliability argument credible, in my _real world_ experience. Indeed, a typical PC processor with reasonably efficient software could easily saturate any automation backplane I've seen and nearly any network designed for automation as well. Indeed, if you were to port the PLC software directly to a PC, which is probably quite doable since many PLCs run x86 engines these days,
all your perceptions of PC speed and efficiency would be blown out of the water. The reliability would amaze you as well.
My point is: If you tried to run the equivalent of Windows on your PLC, it would then be both extremely slow and extremely unreliable. But that is not a problem with the hardware. A typical PC with rotating disks and fans might give away 60% of the mtbf of a PLC. More in a really bad
environment. But without those, the two should be much closer as the electronics aren't as different as they are similar.
The other 99% of the "failures" come from simply running the default software rather than making an intelligent selection _for_ reliability. That's why the telcos and most ISPs and financial exchanges and the massively parallel supercomputer folks don't run Windows. They choose software for reliability.
In other words, if your PC is slower and much less reliable than your PLCs, you have a dire need for different software. But don't blame the PC. Borrow a Tivo and do the math :^)
Regards
cww