PC based Control .vs. PLC

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Phill O'Meley

(Originally posted Mon 09/07/1998)
Without wishing to enter into a slanging match over NT vs Linux or continue in the vein of other threads, I agree that you shouldn’t have to put up with any application crashing an operating system.
I suppose I am from the engineering school that like a challenge and say restores old cars that were less than perfect examples of engineering in their time ie Model T Fords to perfect examples of my skill in making it work. Well, for me making an NT system behave in an acceptable manner was a challenge and with help from a couple of sources we have been damn well successful. I chose the WALTZ / NT path as I was fed up with loosing work because we were perceive as the “Brand X” vendor when the site was using “Brand Y”, Then the bit about the process knowledge comes into it as well.
So please accept my apologies if my comment raised your ire, however, beta max, MAP, and some really great engineering concepts are now dead. Why, because the commercial and marketing forces of our world have a louder voice than the engineering bodies. So instead of trying to stop the tide I thought working with it would feed our employees longer and give us a better start than hose that fight against it.
Regards
Phill O’Meley
PS If you can give me a shrink wrapped soft PLC running on Linux then I would look closely at it........
 
N
(Originally posted Mon, 07 Sep 1998)
Actually, I disagree that IBM and Bill Gates have done more for computing than anyone else. On the contrary, I think that their companies have held back progress in computing. Back when MS and IBM started out, there were already better technical solutions (for that time period) beginning to be commercialized (eg. Digital Research’s CP/M and MP/M and the S-100 bus architecture). These didn’t reach a critical mass because they were abandoned in favour of inferior technology with better marketing. I contend that there has been an incalculable waste of programming time spent on the programming of work-arounds to the deficiencies in MS and IBM technology. What I will give Microsoft and IBM is that they demonstrated that when technology goes up against marketing, marketing usually wins.
Nick
 
(Originally posted Mon 09/07/1998)
You may also note that Octagon Systems, manufacturers of single board computers and Event Technologies, developers of GELLO, an object based programming control language, announced two weeks ago that GELLO would now be available imbedded on the Octagon product offerings! Now you can buy a single board computer, with or without built in I/O, with a ready-to-run control “operating system” no different than a PLC cpu. You design your “logic”, download it through a serial port to the Octagon unit, connect up the I/O and/or terminals and go. Except the Octagon cpu, being a PC (sans any moving parts) has about 10x the flexibility as a brick style plc. Prices start under a $1000. Learn more about it at http://www.gello.com.
 
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Dan Hollenbeck

(Originally posted Tue 09/08/1998)
Correct. The blue screen of death only applies to PC based control products that use Win NT. SoftPLC has it’s own RTOS, which means it controls the source code to the RTOS.
By the way, there are many other PC based control products that don’t use Win NT.
As a PC based control vendor you risk your your personal, product, and company reputations on the controller’s OS. As a customer you risk much much more. Where do you want MS to take you today?
This is also true of the PLC vendors, products, and users, however the PLC’s OS is on the firmware.

Daniel Hollenbeck
SoftPLC Corporation
http://www.softplc.com
[email protected]
 
R
(Originally posted Tue, 08 Sep 1998)
I don’t entirely agree. CP/M was a neat 8 bit operating system (try a 1kbyte BIOS for Z80-good trick), but it faltered in going to the 16 bit world and allowed ms to take over. I did a fair amount of programming in z80 cp/m and thought it was really slick. cp/m86 was slow coming out of the blocks, horribly marketed, and then left to die, but admittedly somewhat superior to msdos (faster, smaller, etc.)
I would argue the s100 bus was as good as the PC bus, but no better and the PC bus is slightly less expensive. The s100 bus also had the bad rap of being a hobbyist bus. This tended to scare off the business users.
What really killed off cp/m wasn’t just ms but also the venders of s/w that never bothered to write s/w for cp/m86. Msdos was what they chose to write s/w for, and with few apps, it withered and died.
 
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Steve Jaeckels

(Originally posted Tue 09/08/1998)
I have seen a lot of comments regarding hard drives and their inability to withstand the rigors of the factory floor. I would like to point out that PC-Based control does not necessarily mean that the PC being used is a consumer model from the shelves of the local Best Buy or Circuit City.
PC-Based control can, and does, take place on a large variety of machines, including a vast array of diskless, single board PCs from companies like Octagon Systems (www.octa.com). These systems offer a multitude of storage and memory options, and have better temperature specs than any PLC (-40 to 70 C). They have been proven over-and-over again in rugged applications - without the problems caused by hard drives.
Eliminate the hard drive issue from your objection list to PC-based controls - it doesn’t belong there.
As for the operating system, the user has a multitude of options. NT is certainly one choice, but the generally accepted assumption that NT is the only way to implement a PC-Based control system is absurd. Still, even with its large storage requirements, NT will soon be able to reside on these small, diskless embedded PCs (disk-on-a-chip is coming out in 160+Meg).
For those who aren’t interested in NT, there are a good number of non-NT solutions for running PC-based controls. They range from DOS-based systems to real-time OSs like QNX.
Eliminate the blue screen issue from your objection list to PC-based controls - it doesn’t belong there.

Steve G. Jaeckels
Manager - Applications/Product Support
Event Technologies, Inc.
 
(Originally posted Tue 09/08/1998)
This is a different question than you first asked.
There is a big difference between errors that occur in the Windows NT world (and can cause a blue screen of death) and runtime errors that occur in the real-time world (as a result of mistakes in my programming).
Steeplechase keeps these two worlds separate. If a blue screen of death happens in NT, the runtime is not affected by it. In fact, the runtime can notice the event and take corrective action.

I have written NT Kernal Mode drivers. In one hour, I can write a program that will cause a blue screen. If I try not to cause blue screens, it takes longer for one to happen. With careful design and thorough testing, I can (and have) create a driver that probably won’t blue screen.
The great blessing of PC based control is that I can use things written by people who have never heard of Steeplechase to make my machine better. If one of those folks writes a driver that causes the blue screen of death, Steeplechase protects the runtime (and my machine, my production, my operator, etc.).
 
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David McGilvray

(Originally posted Tue 09/08/1998)
> PS If you can give me a shrink wrapped soft PLC running on Linux then I would look closely at it........ <

Check out AutomationX at www.mnrcan.com.
David McGilvray
 
M
(Originally posted Tue 09/08/1998)
>Without wishing to enter into a slanging match over NT vs Linux or continue in the vein of other threads, I agree that you shouldn’t have to put up with any application crashing an operating system. ... I chose the WALTZ / NT path as I was fed up with loosing work because we were perceive as the “Brand X” vendor when the site was using “Brand Y”, Then the bit about the process knowledge comes into it as well.<

Unfortunately, its the chicken & egg syndrome.

> So please accept my apologies if my comment raised your ire, however, beta max, MAP, and some really great engineering concepts are now dead. Why, because the commercial and marketing forces of our world have a louder voice than the engineering bodies. So instead of trying to stop the tide I thought working with it would feed our employees longer and give us a better start than hose that fight against it.<

I believe that in a few years, we will see Linux solutions that are currently NT only (or NT mostly), but for now I’ll have to wait.

> PS If you can give me a shrink wrapped soft PLC running on Linux then I would look closely at it........<

While I would prefer something based upon Linux (when it supports real-time without needing patches), Regardless of what OS is running, unless the hardware quality is improved and hard drive are not needed for the system to run, I’ll stick with a PLC. I am pro Linux, be even so, I still feel the PCs in there current state are not good platforms. I would consider a ‘PC’ system with an embedded kernel.
 
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Robert Holman

(Originally posted Tue 09/08/1998)
I have used softPLC on a number of projects (I use both PC and PLC depending on the customer). That is correct, you won’t get the blue screen of death with softPLC. It is like using an A-B 5/25 but it also eliminates some of typical PLC limitations such as scan time (just run with a faster CPU), memory (just add some RAM to your PC box), you can add ethernet communications to talk to the rest of the world and I can talk to it remotly with a modem. And you still have all the functions of the A-B registers to monitor what its doing (yes, via the modem too).

Robert Holman
 
(Originally posted Tue, 08 Sep 1998)
Again, almost true. The story is that Marketing wins everytime over technology. In this case, Gary Kildall, the CEO of Digital Research, refused to meet with Don Estridge and the IBM “suits”, so he left it up to his wife and others. They didn’t do very well at presenting CP/M-86, but IBM decided to offer it with the PC at a significantly higher price than MS-DOS. By the way, IBM went to MS only because BASIC was not available on CP/M-86, but MS supplied BASIC to Apple. Once at MS, Bill Gates found that IBM was intending to offer CP/M-86, so he did an overnight Master Distributor contract with Seattle Microsystems, had his programmers work overnight to construct a demo of it, made the demo to IBM the next day, and offered to allow IBM to private-label it PC-DOS. IBM offered PC-DOS for about $90 and CP/M-86 for about $260. The rest is history and a no-brainer.
Dick Caro
Richard H. Caro, Vice President
Automation Research Corporation
 
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Johnson Lukose

(Originally posted Tue, 08 Sep 1998)
I myself have taken pokes at MS technical holes. It was my point to say that IBM and Microsoft whether by blunder or design made systems affordable and within reach to everyone in this world not just in the USA. Was any CP/M, MP/M or S100 systems available in this part of the world? Could I afford CP/M, MP/M, S100 systems? Do you think the ‘owners’ of CP/M, MP/M or S100 technology would have driven the prices down let alone push the technology as Wintel? What would be the price of an equivalent CP/M, MP/M, S100 systems equalling 80386, 4MB RAM, 250MB Harddisk, VGA, OS in 1990? What would be the price of an equivalent CP/M, MP/M, S100 systems equalling PII-266MHz, 64MB RAM, 4.1GB Harddisk, SVGA, 56K Modem, OS, Winsock, Internet Browser, Internet Mail, Anti-Virus, Audio and Speakers today? I bought mine from Dell for RM5500.00 (~US$1500). Even the books were expensive back then, you could buy a monitor for the price today!
In my country the PC industry had it’s beginnings with the ‘Pineapples’ - Apple clones from Taiwan. The computer shops were sprinkled miles away, almost clandestein, the traders had too, as a slight sneeze from the US and these shops will be raided by the Trade Ministry. Then came the IBM PC, the whole paradigm has turned on the head. Today there is a legitimate computer industry in the billions of RM and perhaps you have heard of MSC (Multimedia Super Corridor) initiative.
NO, I remain - Nobody has done more for computing than IBM and Bill Gates!!
Let’s not take it away from them.
thanks.
 
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Phill O’Meley

(Originally posted Wed 09/09/1998)
I am currently reviewing the Venturecom reduced NT product that may
behave as we would all like to see, I will keep you informed of the
outcome, or is there anybody out there with experience in this product
Regards
Phill
 
N
(Originally posted Tue, 08 Sep 1998)
>I would argue the s100 bus was as good as the PC bus, but no better and the PC
bus is slightly less expensive. The s100 bus also had the bad rap of being a
hobbyist bus. This tended to scare off the business users.<

Back then, I liked the s100 bus architecture better than the PC bus - as it was meant to be modular/open. ie. You could swap CPU boards (say go from a Zilog to an Intel or even to a Motorola CPU) and leave the rest of your hardware intact (memory boards, disk controllers, etc.). Well, that’s the way it worked most of the time. ;-). Also, the s100 bus systems of the day had a 24 line address bus compared to the short-sighted 20 line address bus of the IBM PC. I recall s100 bus systems with 68000 CPUs running UNIX being available at roughly the time that the first IBM PC came out. By comparison, the original IBM PC was a toy and more of a hobby machine than the then extant s100 bus systems.

>What really killed off cp/m wasn’t just ms but also the venders of s/w that
never bothered to write s/w for cp/m86. Msdos was what they chose to write
s/w for, and with few apps, it withered and died.<

Very true, but I still contend that marketing won out over technical merit.
It’s interesting to look back and see the path we took to arrive to where we are today. ;-)
Nick
 
C
(Originally posted Wed 09/09/1998)
> > PS If you can give me a shrink wrapped soft PLC running on Linux then I would look closely at it........ < <
> Check out AutomationX at www.mnrcan.com.<

Thanks for the link to M&R.
This way we could offer a reliable, powerful, non-proprietary product.
Or, if the customer insists, offer it on NT.
Thanks again
Curt Wuollet
Heartland Engineering
 
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Johnson Lukose

(Originally posted Wed 09/09/1998)
If PC based control is about slapping on an Intel microprocessor with everything else proprietary, every man and his dog is offering PC based control. So there is the answer, we no longer need to waste our breath / keyboards on this PLC vs. PC based control debate??
thanks.
 
C
(Originally posted Thu 09/10/1998)
Hi, Nick
The fact that IBM made personal computers legitimate with their marketing muscle wasn’t all bad As I remember, the S100 machines were pretty spendy ( I had a Cromemco) we should give them credit for making them ubiquitous. The bad part is how little thing have changed since then. We still live with a lot of zany engineering “features” of the original IBM’s. (segmented addressing, very limited hardware interrupts, “the BIOS” etc.). As an example of a technically inferior design becoming the “standard”, it rates right on up there with the Windows stuff.
Curt Wuollet
Heartland Engineering.
 
D
(Originally posted Fri 09/04/1998)
>“I don’t know about AB’s Soft-Logix but, SoftPLC has it’s own built-in control logic interpreter just like the AB PLC-5. Therefore, it supports online run-mode programming, and can trap runtime programming errors such as DIV by Zero.
When it is all said and done with, a PLC is just a CPU with an OS that runs a firmware control logic interpreter.
Now if your PC-based control product simply compiled the control logic into machine code you might have to ask some questions.”<

A couple of points need to be clarified here:
a) The “Classic” PLC 5 ran on an interpreter (ex. 5/15, 5/25) b) The “New Platform” PLC5 is compiled (ex. 5/20, 5/40, 5/60, 5/80)
c) The SoftLogix 5 is compiled
d) All of the above support Online Runtime Editing using the same programming software package
e) All of the above are designed to detect and report application parameter errors prior to, and without, passing them to the OS. This prevents critical errors from occurring, and provides the diagnostics that our users need to create stable application code.

>“So with softPLC, I can’t get the blue screen of death?”<

I’d like to answer this question for the SoftLogix 5, using an excerpt from the Q&A document on our http://www.OpenAutomation.com website. There has been significant marketing hype occurring on the BSOD issue. Please see our Whitepaper in this area for more detail on this subject.
Q: Does your technology provide the ability to run after a kernel exception (Blue Screen of Death) in NT?
A: Absolutely not, we believe that this in an inherently unsafe thing to do. It is equivalent to a PLC 5 “red light”. The reasoning behind this is that it is not possible to determine whether or not the kernel exception resulted in the corruption of data in the I/O control and status area of memory. If corruption occurred in this area, I/O cards used in the soft control program could also become corrupt. It is simply not possible to protect this area of memory using today’s PC hardware. Anyone who claims otherwise is either uninformed, or allows for a level of integrity that is considerably less than what we believe is required for control.
Dave Lillie
SoftLogix Extensions Program Manager
Rockwell Software Inc.
http://www.SoftAutomation.com/SLX
 
(Originally posted Wed 09/30/1998)
Just by the way, you can purchase RAID (Redundant Array of Inexpensive Disks ) which will total mirror a hard drive and even allow you to swap a defective one out with the power on. These are very inexpensive starting at $200 raid Level 1 to $1000 Raid Level 5. I have not had a disk failure in years, the latest drives have Mfg. warranties of 5 Years with MTBF of 65000+ hours i.e. 8 years continuos..
Doug
 
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