Hi,

Are there any particular system requirements regarding the PC-hardware or graphics adaptor?

Planning to setup a production machine running Proview under Ubuntu on a new Dell PC:
OptiPlex 755
1.0GB 667MHz NON-ECC DDRII Memory
80GB (7,200rpm) SATA 3.0Gb/s Hard Drive
48X/32X CD-RW/DVD Combo Drive (Dual)

regards
/Ohl

Shouldn't be any problems, proview is not very resource intensive unless you use very fast PLC-threads (10ms or faster) or have _very_ large PLC-programs, or own applications that take a lot of CPU.
The first Linux versions of proview here at SSAB was run on PIII 550 MHz without any problems.

The graphics doesn't matter at all for performance, but I can recomend at least 1280x1204 to get reasonable workingspace for developing PLC-programs.

As for the operator interface I would recommend at least the same, but preferable 20\" @ 1600x1200.
But i really depends of the information-density in the GE-images.

/Ulf

Ok, but 10ms doesen´t sound very fast from my point of view. In many conventional PLC systems 3-4ms is normal cycle times. Is it the hardware or the sofware that limits the cycle time?

regards
/Ohl

It's mainly the software.
The linux kernel (like most other operating systems) has a interrupt timer than handles the process scheduling of all the processes on the computer.
Until just a few years ago that timer run on 100Hz of historical reasons, wich made process scheduling impossible more often than every 10ms. (ie the absolutley fastest scheduling for an PLC-program would be 10ms)
Now you can choose when you build a custom kernel if you want to run on 100,250 or 1000Hz giving a minimum scheduling time of 1ms.
As far as I know you have to recompile your kernel to change the scheduling speed, and ubuntu probably is running 250Hz by default.

That explained I really think you should consider what speeds you need.
We have a lot of heavy, fast machinery that requires exact movement and posistioning here at SSAB and we rareley need go below 20ms in thread speed in spite of that.
I would say that of around 250 systems we have 2 or 3 running threads on 10ms, and I think 2 of them is dust filters were the cleaning air-pulse length is the critical part.

Also, a modern computer is a bit faster at executing PLC-programs than your average standalone hardware PLC.
So a soft PLC in a PC is a little bit of a tradeoff, maybe you don't get the same scheduling speed for programs as a standalone-PLC, but it can run much larger programs without taking any more time each scheduling cycle, hence giving your more flexibility.

Is there any specific part in your line that you think requires faster scheduling than 20ms and why?

/Ulf

No, not in this particular project. This is a slow process and Proview will, at least to start with, mainly be used to set and synchronize the speed of a number of frequency converters, and of course to give the operators a nice GUI!

But if one would like to control for example a flowpack machine which needs to handle a product flow of about 100-200 pieces per minute cycle time might become critical.

But then again, I agree on that most processes will run perfectly at 20ms or even 100ms cycle times.

Regards
/Ohl

How can I see the actual scheduling frequncy in Ubuntu (and perhaps other distro´s)?

/Ohl