Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1999-09-09
2002-04-16
Beausoleil, Robert (Department: 2785)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C710S100000, C327S142000
Reexamination Certificate
active
06374365
ABSTRACT:
The present invention concerns a device for operating two functionally parallel computers.
Processors of this kind are used in digital computers. Computers of this kind are either fixed-programmed automatic control systems or programmable computers, mainframe computers, and PCs.
The main components of such computers are the input and output means, the memory, the processor, and the clock generator.
The input and output means and the memory are customarily designated as peripherals. Processors may be divided into a processing processor and an input-output processor. In the conventional PCs of today, the processing and the input-output processors are combined into the “processor.” Nevertheless, the present invention pertains to individual processors such as processing processors and input-output processor of mainframe computers and the conventional “processors” of PCs and home computers of today. When processors are referred to alone below, the above variants are included. The control of peripherals takes place through the processor via bus lines. The processing clock pulses of the processor are provided by the clock signal generator. This is a continuous time signal series, the processor carrying out a predetermined computational process with each clock signal. The frequency of the clock signals is therefore a direct measure of the computational speed of the processor. The computational speed of the processor is therefore to be matched with respect to the frequency of the clock signal generator such that one computational operation is completed before the next clock pulse comes.
Processors are very highly integrated semiconductor circuits which naturally are subject, even under the most precise manufacturing conditions, to a certain degree of manufacturing tolerance. The processing reliability of the processors, however, is not thereby impaired. Within the specified manufacturing tolerance, the functioning reliability of the processor is always present, as long as disturbances do not impair processing reliability.
The danger does indeed exist that the function of a processor can be impaired through external disturbances. These disturbances are coupled into the computer through electrical or magnetic fields from the outside and cause the induction of voltages in conductive parts and conductive connections of highly integrated processors.
The induced voltages occur stochastically and are independent of clock. They elicit interference currents. These interference currents are superimposed on the currents within the processor and in the process induce unpredictable malfunctions.
These induced voltages can therefore result in information which comes from the processor unit to the memory modules being corrupted.
This corruption leads to undesired results in the output data of the computer. If the data transferred represent program steps, often a malfunction will occur due to accidentally interrupted programs or programs which are continued at some other, erroneous place. The effects are again undesired actions of the processor.
There are already efforts to increase the operating reliability of processor-controlled devices. In the arrangement according to DE-OS 26 12 100 (German Published Patent Application 26 12 100), two complete computers are connected in parallel and the output signals of the two computers are compared to each other in a seal-in circuit. After the comparison clock pulse comes the next active processing clock pulse.
The seal-in circuit forms a functional module in which the applied individual, synonymous output signals of the two processors are sequentially compared with each other. This takes place via a query sequence which does not pass over to the next signal until the prior signal has been checked. Since there are always numerous synonymous signals at the bus conductors to check, the sequential query of the individual synonymous signals is associated with considerable expenditure of time. Only after running through the entire query sequence is the next valid clock pulse then transmitted to the processors if all synonymous output signals are in agreement.
The progress of computation for the two processors in DE OS 26 12 100 is thus dependent on the passthrough time needed to check the output signals of the preceding work pulse for agreement.
Other customary solutions—in particular those for applications with very high reliability requirements in the fields of aviation and space travel—consider the entire computer, comprised of processor, memory, and inputs and outputs, as a closed unit. It is then assumed that this unit can generate undesired results at the outputs. For this reason, the entire computer is made redundant, for example threefold or fivefold design, and the outputs are connected through suitable coordinating elements such that the possibly false results of one of the computers is agreed with the results of the other computers.
This multiple design of the computer components, however, always creates high costs. Except for special individual applications, however, these costs are not justified. Nevertheless, for applications with higher reliability requirements, an increased disturbance reliability and improved processing reliability is desired.
In industrial control technology, there are such applications with a high degree of reliability requirement, for example, for machine controls and in drive technology. In these applications, malfunctions of a controlling computer can cause great material damage. The redundant design of the computer, however, often is out of the question for reasons of cost. Therefore safety-relevant functions such as end disconnects are often installed in separate hardware, for example via external sensors, switches, and actuators, to which the controlling computer does not have access. In this way, important disconnection operations can be carried out even with the loss of the controlling computer. This parallel-installed technology, however, also often causes high costs which must be incurred in addition to the costs for the actually desired control function of the computer. Furthermore, the external accessory systems restrict the functionality and flexibility which are the very reason the computer is utilized.
In addition, a so-conceived disconnect does not intervene in the process until a malfunction of the machine which is to be controlled occurs and can no longer be reversed.
Therefore the external accessory devices are also given the task of stopping the ongoing process in a timely manner such that despite the error in the controlling computer which has occurred, material damage is prevented.
Therefore the functional relationships between the process parameters and any malfunctions of the computer must be analyzed in advance so that they can be recognized in time by emergency stop controls controlled in this manner.
The complexity of systems of this kind therefore presupposes a full measure of external accessory equipment in order to be able to detect all probable eventualities in a timely manner in order to be able to execute the necessary emergency stop.
The object of the invention is to further develop the known device such that a processor circuit with increased operation reliability is realized while maintaining the safety requirements and at the same time having increased possibilities for application in industry.
The invention provides the advantage that without loss of computer performance and with low costs, the operating reliability of the computer is disproportionately increased.
The disproportionate increase is based on the fact that the probability of simultaneous loss of two processors is less by an order of magnitude than the probability of the loss of a single processor.
Since the invention can be used with processors of any kind, thus also with input/output processors, processing processors, and mathematical co-processors, there is the additional advantage that in a targeted manner, it is possible to provide only certain types of processors in a computer with the increased operating reliability.
What
Beausoleil Robert
Pandiscio & Pandiscio
Ziemer R
LandOfFree
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