Abstract:
When errors arise in a computing system that has plural modules, this invention corrects those errors. In the first instance, the invention excludes the computing system itself, but receives error messages from the plural modules of that system—along plural receiving connections, respectively. Plural sending connections return corrective responses to plural modules of that system, respectively. In a second instance, the invention further incorporates that system. The invention is hierarchical: plural levels or tiers of apparatus and function are present—a first (typically uppermost) one directly serving that system as described above, and others (lower) that analogously serve the first tier of the invention—and than also the subsequent tiers, in a cascading or nested fashion, down to preferably a bottom-level tier supporting all the upper ones. Each level preferably controls power interruption and restoration to higher levels. Ideally the hierarchy is in the form of a “system on chip”.

Description:
RELATION BACK 
       [0001]    This patent document claims priority of my provisional application 60/709,492, filed Aug. 19, 2005. 
     
    
     BACKGROUND 
       [0002]    There exists a paradox in contemporary computing systems: they are used to protect various critical infrastructures of our society, such as electrical power, transportation, communication, etc., but they possess no identifiable error-detecting and -correcting infrasystem of their own. Such an infrasystem, or support architecture, should be (1) generic—that is, suitable for a variety of “client” computing systems—and (2) transparent to the client&#39;s software, but able to communicate with it, (3) compatible with and able to support other defenses that the client system employs, and (4) fully self-protected by ability to tolerate faults, immune to the client system&#39;s faults, including design faults, and to attacks by malicious software. 
         [0003]    My present invention is an error-detecting and -controlling architecture with the above properties, imparting resilience to the overall computing system. My invention is preferably implemented entirely in hardware, to maximize system error-controlling dependability. 
         [0004]    The following sections discuss conventional methods of noting and controlling errors in high-availability systems, and their shortcomings, and a principle of design I call “the immune system paradigm”. 
         [0005]    Error-sensing and -correction defenses in current high performance and availability platforms (servers, communication processors, etc.) are found at four different hardware levels: component (chip, cartridge, etc.), board, platform (chassis), and group of platforms 
         [0006]    C OMPONENT  L EVEL  F AULT  T OLERANCE —At the component level, the error detection and recovery mechanisms are part of the component&#39;s hardware and firmware. In general, we find very limited error detection and poor error containment in commercially available processors. For example, in Pentium and P6 processors error detection by parity only covers the memory caches and buses, except for the data bus which has an error correcting code, as does the main memory. All the complex logic of arithuretic and instruction processing remains unchecked. Recovery choices are “reset” actions of varying severity. The cancellation in April 1998 of the duplex “FRC” mode of operation eliminated most of the error containment boundary All internal error detection and recovery logic remains entirely unchecked as well. 
         [0007]    Similar error coverage and containment deficiencies are found in the high-end processors of most other manufacturers. The exceptions are IBM S1390 G5 and G6 processors that internally duplicate the arithmetic and instruction handling units and provide extensive error detection or correction and transient recovery for the entire processor. Near 100% error detection and containment are attained in the G5 and G6 processors, which carry on the legacy of fault tolerance from the IBM 9020—the last mainframe. 
         [0008]    Intel too has an early record of building error-removal systems. The original design of the Pentium and P6 family of processors (except P4) includes the FRC (functional redundancy checking) mode of operation. In FRC two processors operate as a master checker pair that receives the same inputs. The checker internally compares its outputs to those of the master and issues the FRCERR signal when a disagreement is found. The master enters the Machine Check state upon receiving FRCERR. Operation in FRC mode provides near 100% error detection at the master&#39;s output and also makes the output an error containment boundary. 
         [0009]    In April 1998, however, a set of specification changes was issued by Intel: “The XXX processor will not use the FRCERR pin. All references to these pins will be removed from the specification.” (The “XXX” stands for all processors from Pentium to Pentium 111.) Deletion of FRC mode left the Pentium and P6 processors with very limited error detection and containment. No further explanation was provided by Intel for the change. My conjecture is that asynchronous inputs could not be properly handled in the FRC mode. Intel did not reply to my inquiry about the cause of FRC deletion. 
         [0010]    Processors that do not have adequate error detection and containment can be made fault-tolerant by forming a self-checking pair with comparison (e.g., the FRC mode) or a triplet with majority voting on the outputs. Since the FRC mode deletion, there is a second deficiency of contemporary processors: they do not (or cannot) provide hardware support for comparison or voting operations. 
         [0011]    F AULT  T OLERANCE AT  H IGHER  L EVELS —At the board level, complete redundant hardware as well as software components are used to assure very high availability. The “hot standby” approach is especially widely used in the fields of embedded systems and telecommunications. Hot standby duplexing selectively duplicates the most critical subsystems, such as the CPU, power supplies, cooling fans, etc. Less costly error-containment techniques such as ECC, RAID, N+1 sparing, etc. are used for the remaining subsystems. The CPU boards present the greatest challenge: to detect faults in both CPUs and to execute a rapid switchover to the hot standby CPU when the active CPU is faulty. A good example of the state-of-the-art is the Ziatech high availability architecture. The critical elements that execute CPU switchover are three hardware modules and four software modules for each CPU. These modules must be operational to make a switchover possible, but they are not protected by fault tolerance themselves. 
         [0012]    At the platform level a widely used technique is Intelligent Platform Management (IPM) that requires the introduction of the IPM hardware subsystem into the platform(s). It consists of additional on-the-market hardware (buses and controllers) and firmware that provides autonomous monitoring and recovery functions. Also provided are logging and inventory functions. The effectiveness of the IPM monitoring and recovery actions is limited by the error information outputs and recovery commands of the conventional processors of the platform. For example, the P6 processors have only a set of “reset” commands and five error signals (after deletion of FRCERR) whose coverage was estimated to be very limited. 
         [0013]    Known IPM subsystems are not themselves protected by error containment or resilience. The cost of adding such attributes may be high because of the multiple functions of the IPM. The Version 1.5 of the IPM Interface Specification (implementation independent) has 395 pages, which represent a lot of functionality to be protected. Furthermore, the IPM does not support comparison or voting for redundant s multichannel (duplex or triplex) computing. A cluster is a group of two or more complete platforms (nodes) in a network configuration. Upon failure of one node, its workload is distributed among the remaining nodes. There are many different implementations of the generic concept of “clustering”. Their common characteristic is that they are managed by cluster software such as Microsoft Cluster Service, Extreme Linux, etc. The main disadvantages for telecommunication or embedded systems are: (1) the relatively long recovery time (seconds); and (2) the cost of complete replication, including power consumption, replication of peripherals, etc. 
         [0014]    The four approaches discussed above are at different levels and can be implemented in different combinations. The integration of the different error detection, recovery and logging techniques is a major challenge when two or more approaches are combined in the same platform. 
         [0015]    T HE  D ESIGN -F AULT  P ROBLEM —None of the approaches described above addresses the problem of tolerating design faults in hardware (“errata”) and in software (“bugs”) of the COTS processors. Yet a study of eight models of the Pentium and P6 processors shows that by April 1999 from 45 to 101 errata had been discovered, and from 30 to 60 had remained unfixed in the latest versions (“steppings”) of the processors. The discovery of errata is a continuing process. For example, consider the Pentium III. The first specification update (March 1999) listed 44 errata of which 36 remained unfixed in five steppings (until May 2001). From March 1999 to May 2001 35 new errata were discovered of which 22 remained unfixed. Other manufacturers also publish errata lists, but those of Intel are most comprehensive and well organized. 
         [0016]    Most of the errata are triggered by rare events and are unlikely to cause system failures; yet the designers of error-sensitive systems cannot ignore their existence and the fact that more errata will be discovered after a system design is complete. Continuing growth of processor complexity and the advent of new technologies indicate that the errata problem will remain and may get worse in the future. 
         [0017]    The most effective method of error detection and containment, particularly including errors arising in the design stage, is design diversity, i. e., multichannel computing in which each channel employs independently designed hardware and software, as in the Boeing 777 Primary Flight Control Computer. The Boeing and other diverse designs employ diverse COTS processors and custom hardware and software because few or no commercially available processors support multichannel computing. Design-spawned error correction by means of design diversity will become much less costly if it can be supported by commercially available hardware elements. It is also important to note that design diversity provides support for the detection and neutralization of malicious logic. 
         [0018]    L IMITATIONS OF THE  F OUR  A PPROACHES —The implementation of defenses at all or some of the above described four levels has led to the market appearance of many high-availability platforms (advertised as 99.999% or better) for server, telecammunications, embedded and other applications; however, all four approaches show deficiencies that impose limits on their effectiveness. 
         [0019]    At the component level the Intel P6 and Itanium processors, as well as those of most other manufacturers (except IBM&#39;s G5 and G6) have a low error detection and containment coverage, leaving instruction handling and arithmetic entirely unchecked. After executing the Reset command most of the existing checks (bus EPC, parity, etc) are disabled and must be enabled by software that sets bits in the (unprotected) Power-On Configuration register. In general, critical recovery decisions are handed off to software. 
         [0020]    At the board level, such as in “hot standby”, unprotected “hard core” hardware and software elements handle the critical switchover procedure. 
         [0021]    At the platform level the Intelligent Platform Management (IPM) hardware subsystem handles both critical recovery decisions and voluminous logging, configuration record keeping and communication management operations. The critical IPM element is the Baseboard Management Controller (BMC) that is itself unprotected and depends on interaction with software to carry out its functions. 
         [0022]    At the cluster level that is software-controlled the disadvantages are long recovery times and the high cost of complete system (chassis) replication. 
         [0023]    In summary, the weaknesses are: 
         [0024]    1. the presence of unprotected “hard core” elements, especially in the error detection and recovery management hardware and software; 
         [0025]    2. the commingling of hardware and software defenses: both must succeed in order to attain recovery; 
         [0026]    3. the absence of built-in support for multiple-channel computing that provides high coverage and containment, especially when design diversity is employed to attain design-fault tolerance. 
         [0027]    It is my conclusion that during the explosive evolution of hardware over the past 25 years, computer hardware has not been adequately utilized for the assurance of error containment. This observation is not intended to unduly criticize or derogate the efforts of the very many talented and diligent workers in this field; however, these are exceedingly difficult problems, and the state of the art does leave ample room for refinements. 
       SUMMARY OF THE DISCLOSURE 
       [0028]    The present invention introduces just such refinements. In preferred embodiments of its main aspects or facets, the invention is apparatus for controlling errors in a computing system that has plural modules. The apparatus includes a hierarchical error-correcting system. 
         [0029]    It also includes at least two receiving connections, for reception by the hierarchical system of error messages from the plural modules of the computing system, respectively. In addition it includes at least two sending connections, for return by the hierarchical system of corrective responses to the plural modules of the computing system, respectively. 
         [0030]    The foregoing may represent a description or definition of the first aspect or facet of the invention in its broadest or most general form. Even as couched in these broad terms, however, it can be seen that this facet of the invention importantly advances the art. 
         [0031]    In particular, this first aspect of my present invention can not only resolve the previously outlined problems for each of the four levels considered singly—i. e., the component, board, platform, and cluster or “group” levels—but also provide resolution of those probleams on an integrated and therefore extremely efficient basis. That is, the first facet of the invention deals with all four levels considered as an architecture or structure. The above-defined invention thus a provides error correction and containment from a hierarchical apparatus one that can substantially parallel the hierarchy of the computing system itself. 
         [0032]    The “computing system” mentioned above, in this broadest definition, is not itself part of the invention as most broadly defined—but rather is only a part of the context, or environment, of the invention. In other words, as the broadest of the appended claims make clear, a person who makes, uses or sells the error-controlling apparatus but not the computing system is making, using or selling my invention for purposes of infringement; however, as others of the appended claims also make clear, the computing system can be separately added into the defined invention, for purposes of defining infringement. 
         [0033]    Although the first major aspect of the invention thus significantly advances the art, nevertheless to optimize enjoyment of its benefits preferably the invention is practiced in conjunction with certain additional features or characteristics. In particular, preferably the hierarchical system comprises at least two first-level (i. e., “top level”) errors/corrections caches. 
         [0034]    Each first-level errors/corrections cache holds:
       a listing of error messages which respective modules of the computing system can send via one of the at-least-two receiving connections, and   a listing of respective corrective responses which respective modules of the computing system can receive via one of the at-least-two sending connections.       
 
         [0037]    In addition each first-level errors/corrections cache comprises preprogrammed means for responding to receipt of any of the listed error messages from its respective module or modules by returning a respective corrective response. 
         [0038]    Another preference is that the hierarchical system further include at least one second-level errors/corrections cache having:
       at least two receiving connections for receiving error messages from the at least two first-level errors/corrections caches, respectively, and   at least two sending connections for returning corrective responses to the at least two first-level errors/corrections caches, respectively.       
 
         [0041]    In yet another preference, the at least one second-level errors/-corrections cache comprises at least two second-level errors/corrections caches. The at least one second-level errors/corrections cache further includes at least one third-level errors/corrections cache having:
       at least two receiving connections for receiving error messages from the at least two second-level errors/corrections s, respectively, and   at least two sending connections for returning corrective responses to the at least two second-level errors/-corrections caches, respectively.       
 
         [0044]    Still another preference is that the apparatus further include at least one bottom-level errors/corrections cache that is supported by a “hypothalamus” module as described in this document. That module has some preprogrammed means for controlling interruption and restoration of power to the at least one bottom-level errors/corrections cache. The bottom-level errors/corrections cache is at an immediately higher level of the hierarchy, from the hypothalamus 
         [0045]    Another preference is that the apparatus additionally include at least one relatively higher-level errors/corrections cache, at a level above the bottom-level errors/corrections cache, supported by another hypothalamus having preprogrammed means for controlling interruption and rcacheestoration of power to the at least one relatively higher-level errors/corrections cache. In this way the relatively higher-level errors/corrections cache can continue in operation if the first-mentioned hypothalamus (i. e., the hypothalamus that supports a bottom-level errors/corrections cache) fails. 
         [0046]    Still another preference is that the apparatus also include—at further levels intermediate between the at least one third-level errors/corrections cache and the at least one bottom-level errors/corrections cache—one or more further errors/corrections caches. These errors/corrections caches are nested in substantially the same way as are the first-, second- and third-level errors/corrections caches introduced above. 
         [0047]    If the plural computing-system modules include at least two diverse processors or programs, or both—for generating parallel candidate results from generally parallel computations in the at least two diverse processors or programs, respectively—then the apparatus preferably also includes at least one conflict-resolver module that campares the parallel results and eliminates one or more of the results. It is to be understood, however, that such comparison and elimination is not limited to top-level modules, e. g. not limited to comparison and elimination of results from computing-system modules. Rather, the use of conflict resolvers can be applied to results from any, or even substantially all, of the errors/corrections caches in my hierarchical system. 
         [0048]    Another preference is that at least one of the first-level errors/corrections caches, or indeed any errors/corrections cache, include in its respective listing an error-controlling message that removes power from the computing-system module (or other module) whose results are eliminated. A related preference is that at least one of the errors/corrections caches includes in its respective listing a corrective message that inserts, powers up and provides initial data for a spare unit in place of such computing-system module (or other module) whose results are eliminated. 
         [0049]    It is further preferred that at least the error-correcting system be in the form of a so-called “System on Chip” or “SoC”. People skilled in this field will understand that the computing system too can be included in the same chip as desired. 
         [0050]    In preferred embodiments of its second major independent facet or aspect, the invention is a method of correcting errors in a computing system that has multiple modules in a hierarchical configuration. The method includes these steps: 
         [0051]    1) providing a hierarchical error-controlling system having a configuration that very generally parallels the hierarchical configuration of the computing system; 
         [0052]    2) providing a multiplicity of interconnections between elements of the computing system and corresponding elements of the very generally parallel error-controlling system, respectively; and 
         [0053]    3) in event of errors by elements of the computing system:
       passing error messages from the computing-system elements to the corresponding error-correcting-system elements, by way of the interconnections, and   returning corrective messages from the error-correcting-system elements to the computing-system elements, by way of the interconnections.       
 
         [0056]    The foregoing may represent a description or definition of the second aspect or facet of the invention in its broadest or most general form. Even as couched in these broad terms, however, it can be seen that this facet of the invention importantly advances the art. 
         [0057]    In particular, analogously to the advancement provided in regard to the above-discussed first facet of the invention, the above-defined second aspect of the invention provides error control and containment from a hierarchical apparatus that not only can but expressly does generally parallel the hierarchy of the computing system itself. 
         [0058]    Although the second major aspect of the invention thus significantly advances the art, nevertheless to optimize enjoyment of its benefits preferably the invention is practiced in conjunction with certain additional features or characteristics. In particular, preferably the various apparatus preferences of the first, apparatus aspect of the invention are practiced in relation to this second, method facet of the invention as well. 
         [0059]    In preferred embodiments of its third major independent facet or aspect, the invention is apparatus that comprises—in a single combination—all or almost all of the features and relationships mentioned above in connection with the first aspect of the invention and its related preferences. Here too, the error-corrected computing system is for some purposes regarded as part of the invention environment or context, and for other purposes regarded as part of the invention itself—all as more specifically set forth in the various appended claims. The preferences described as to the first facet of the invention are applicable in regard to this third aspect too. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     1. A DESIGN PRINCIPLE: THE IMMUNE SYSTEM PARADIGM 
       [0060]    At the beginning of this document, I identified four attributes that were needed by an error-correcting resilience assembly, which I see as the “missing link” in the defenses of conventional systems, as reviewed in the preceding section. The basic error-correcting assembly, considered alone, is not the present invention; rather, the invention here goes beyond the basic error-correcting assembly. That basic assembly, however, will be introduced first—in this section and sections 2 and 3 below. 
         [0061]    The basic error-correcting assembly should be generic, transparent to client software, compatible with defenses used by the client, and fully self-protected. It appears that an all-hardware assembly is most likely to meet those goals, since stored programs do not need to be protected. The assembly needs nonvolatile storage for record-keeping and ROM microcode for sequencing operations. 
         [0062]    One way to appreciate the requirements and characteristics of my proposed error-controlling assembly is to analogize it to the immune system of the human body. To develop this reasoning, I use the following three analogies: 
         [0063]    1. the body is analogous to hardware, 
         [0064]    2. consciousness is analogous to software, 
         [0065]    3. the immune system is analogous to my novel error-controlling assembly, or resilience support architecture. 
         [0066]    Four fundamental attributes of the immune system are particularly relevant: 
         [0067]    1. It functions (i. e., detects and reacts to threats) continuously and autonomously, independently of consciousness. 
         [0068]    2. Its elements (lymph nodes, other lymphoid organs, lymphocytes) are distributed throughout the body, serving all its organs. 
         [0069]    3. It has its own communication links—the network of lymphatic vessels. 
         [0070]    4. Its elements (cells, organs, and vessels) themselves are self-defended, redundant and in several cases diverse. 
         [0071]    Now I can identify the properties that the error-controlling assembly must have in order to justify the immune-system analogy. They are as follows. 
         [0072]    1a. The assembly consists of hardware and firmware elements only. 
         [0073]    1b. The assembly is independent of (requires no support from) any software of the client platform, but can communicate with it. 
         [0074]    1c. The assembly supports (provides protected decision algorithms for) multichannel computing of the client platform, including diverse hardware and software channels to provide design-fault tolerance for the client platform. 
         [0075]    2. The assembly is compatible with (i. e., protects) a wide range of client platform components, including processors, memories, supporting chipsets, discs, power supplies, fans and various peripherals as well. 
         [0076]    3. Elements of the assembly are distributed throughout the client platform and are interconnected by their own autonomous communication links. 
         [0077]    4. The error-controlling assembly is fully resilient itself, requiring no external support. It is not susceptible to attacks by intrusion or malicious software and is not affected by natural or design faults of the client platform. 
         [0078]    A different and independently devised analogy of the immune system is the “Artificial Immune System” (AIS) of S. Forrest and S. A. Hofmeyr. Its origins are in computer security research, where the motivating objective was protection against illegal intrusions. The analogy of the body is a local-area broadcast network, and the AIS protects it by detecting connections that are not normally observed on the LAN. Immune responses are not included in the model of the AIS, while they are the essence of my assembly. 
       2. Architecture of the Elemental Error-Correcting Assembly 
       [0079]    The unit error-correcting assembly is a system composed of four types of special-purpose controllers, modules  42  through  46 , and closely associated elements  21  through  24  ( FIG. 1 ). These modules are ASICs (application-specific integrated circuits) that are controlled by hard-wired sequencers or by read-only microcode. 
         [0080]    This assembly of correction modules serves and protects a primary-function module  41  that is essentially a conventional computing block such as a standard processor. The primary-function module  41  is a client system, in the sense that it is this module that performs the computing work which the entire computing system exists to perform. 
         [0081]    In some of the appended claims, this protected conventional canputing block  41  is treated as part of my invention itself, and in other claims it is instead treated as a part of the context or environment of my invention. 
         [0082]    Redundant modules (not shown) are provided for fault tolerance of the apparatus itself. One interface module  42  is provided for each primary-function module  41 . All error-signal outputs  32  and recovery-command inputs  33  of the primary-function module  41  are connected through its interface module  42 . Within the assembly  42 - 46 ,  21 - 24 , all interface modules  42  are connected to one errors/corrections cache  44  via the errors/corrections bus  34 . 
         [0083]    Each interface module also has a direct input (the error-alert pin  45 ) to the errors/responses cache  44 . An interface module  42  conveys primary-function module error messages  32  to the errors/corrections cache  44 . It also receives recovery commands  33  from the errors/corrections cache  44  and issues them to the primary-function module  41  inputs. The error-alert pin  45  serves to request errors/corrections cache  44  attention for an incoming error message  32  on the errors/responses bus  34 . 
         [0084]    The errors/corrections cache  44  stores in ROM all error signals from every expected type of primary-function module  41 , and also all prepared responses to those known error types—as well as the sequences for its own recovery. This “errors/corrections cache” also stores system configuration and system time data, and its own activity records—these three functions necessarily of course being read/write. 
         [0085]    The errors/corrections cache  44  is also connected to the so-called “hypothalamus” module  46 . As will be seen, this module is named aptly in that it is one element of the assembly which never powers down completely, and it maintains function (or nonfunction, as may be the case) of all the other modules at a very fundamental level. 
         [0086]    More specifically, the functions of the hypothalamus  46  are to control power-on and power-off sequences for the entire system, to generate fault-tolerant clock signals and to provide nonvolatile, radiation-hardened storage for system time and configuration. The hypothalamus has a reserve electrical source (a battery)  23  and remains on at all times during the life of the error-controlling assembly  21 - 24 ,  31 - 38 ,  42 - 46  and the primary-function module  41 . 
         [0087]    The conflict-resolver module  43  provides resilient comparison and voting services for the other modules. If there are plural primary-function modules  41 , especially diverse processor types and perhaps operating multiversion software, then the resolver  43  includes decision algorithms for handling possibly divergent computation results from such diverse software or processors in the primary-function modules  41 . Fast response of the resolver  43  is facilitated by hardware implementation of such algorithms. 
         [0088]    This same conflict-resolver module  43  also keeps a log of disagreements in the decisions. Another function of the resolver  41  is to serve as a communication link between the software of the primary-function module or modules  41  and the errors/corrections cache  44 . Primary-function modules  41  may request configuration and errors/correction cache-activity data or send power-control commands, and some of these advantageously pass via the resolver  43 . The resolver  43  is linked by a built-in interface  42  to the errors/corrections cache  44 . 
         [0089]    Another function of the resilient error-controlling assembly  21 - 24 ,  31 - 38 ,  42 - 46  is to provide resilient power management for the entire system, including individual command-resettable breakers  24  (essentially power switches) for each primary-function module  41 . Every module except the hypothalamus  46  has such a breaker. The upper-level modules of the assembly as a group have their own resilient operational electrical source  21 . The errors/corrections cache  44  and hypothalamus  46  have a separate “support” source  22 . 
       3. Resilience of the Assembly 
       [0090]    The partitioning of the error-correcting assembly is motivated by the need to make it resilient. The interface and resolver  42 ,  43  are self-checking pairs, since high error-detection coverage is essential, while spare primary-function and resolver modules  41 ,  43  can be provided for recovery under control of the error-response commands stored in the errors/corrections cache  44 . The errors/corrections cache  44  should be continuously available; therefore the system advantageously uses triplication and voting (TMR), with spare errors/corrections caches added for longer life. 
         [0091]    The hypothalamus  46  manages errors/corrections cache replacement and also shuts the system down in case of catastrophic events (temporary power loss, heavy radiation, etc.). The hypothalamus functions are advantageously protected by provision of two or more self-checking hypothalamus pairs (not shown), each with its own backup electrical source. In my development of this invention, I separated the hypothalamus from the errors/corrections cache to make the apparatus cluster (that is to say, a “hypothalamus cluster”  46 ) that must survive catastrophic events as small as possible. 
         [0092]    The all-hardware implementation of the assembly makes it safe from software bugs and external attacks. The one exception is the power management command from the primary-function module  41  to the errors/correction cache  44  (via the resolver  43 ) which could be used to shut the system down. Special protection is needed here. The adverse influence of any hardware design faults in the resilient assembly can be minimized by design diversity, both of self-checking pairs and of errors/corrections caches; however, the logic of all the modules is very simple and it their complete verification should be possible. 
         [0093]    When interconnected, the modules  42 - 46 ,  21 - 24  of my assembly and the typically conventional primary-function module  41  form a computing system that is protected against most causes of system failure. This system is the first example of an implementation of the immune system paradigm. 
         [0094]    The use of the resilient support assembly is likely to be affordable for most computer systems, since the interface, errors/corrections cache, resolver and hypothalamus cluster  42 ,  44 ,  43   46  have simple internal structure. Some truly challenging missions can be justified only if their computers, together with my resilient assembly, have very high coverage as to design faults and as to catastrophic transients due to radiation. Extensive sparing and efficient power management can also be provided by the resilient assembly. 
         [0095]    Given that the MTBF of contemporary processor and memory chips is approaching 1000 years, missions that can be contemplated include the 1000-day manned mission to Mars with the dependability of a 10-hour flight in a commercial airliner. Another possibility is unmanned very-long-duration interstellar missions, using a fault-tolerant relay chain of modest-cost spacecraft—using my resilient assembly particularly as described in this document. 
         [0096]    One thrust of my error-controlling resilient assembly, described above, is to use hardware more extensively and more effectively than is done conventionally in providing resilience for very dependable high-performance platforms. 
         [0097]    My basic resilient-assembly invention, as set forth above, considerect Intel&#39;s P6 family of processors and their supporting chipsets as the commercially available elements of the host platform. These elements were not designed to utilize my resilient assembly, which accordingly is introduced by a “retrofit.” 
       4. A Hierachical Architecture 
       [0098]    As noted earlier the basic, or unit, error-correcting assembly introduced just above—considered alone—is not itself the present invention. I shall now move on to describe preferred embodiments of the present invention. 
         [0099]    This invention is an extension of the basic resilient assembly. Preferred embodiments incorporate the basic assembly into a hierarchical form, together with packaging of the entire hierarchical resilience support system into a single “System on Chip” (“SoC”). 
         [0100]    It is to be understood that the hierarchical configuration can be used without building the system as an SoC. The two together, however, make the invention a particularly powerful combination. 
         [0101]    Each primary-function module  1   a ,  1   b  . . . ( FIG. 2 ) of the SoC is provided with an interface  2   a ,  2   b —similar to the interface  42  ( FIG. 1 ) of the resolver  43  in the basic assembly. As mentioned earlier, use of resolver modules (or interfaces, or both) in my hierarchical assembly is by no means restricted to the upper-level modules that most directly protect and support primary-function computing systems. 
         [0102]    To the contrary, resolvers or interfaces, or both, provide a broad capability useful throughout preferred embodiments of my invention. For example they are advantageously used as well to compare, and make decisions about, results from any of the modules—e. g., intermediate- or even lower-level errors/corrections caches—in my hierarchical system. 
         [0103]    Not all protected activity begins at the first (i. e. top) level. For instance a monitor, or printer, or any number of other single replaceable items, may be found in a lower level—serving errors/corrections caches etc. in the lower tiers of either the primary apparatus hierarchy or my parallel protective hierarchical error-controlling system. 
         [0104]    Errors/corrections caches  5   a ,  5   b  are separate blocks within the SoC, and the errors/corrections bus  4  connects the errors/corrections caches, as a cluster, to each block of the SoC that also has the individual error-alert pins  3   a ,  3   b  connected to the errors/corrections cache  5   a . The resolver  43  ( FIG. 1 ) can also be replaced by a “resolver port” that is part of the SoC block. The SoC has a complete built-in basic resilient assembly, as described above. 
         [0105]    The hierarchical refinement of my resilient-assembly concept takes place as follows. The errors/corrections cache cluster  5   a  of one SoC 1—i. e., errors/corrections cache SoC    5   a —serves as the interface  42  ( FIG. 1 ) of the SoC, with respect to a lower-level errors/corrections cache cluster, errors/corrections cache BOARD    8  that protects several SoC packages located on the same board. 
         [0106]    This errors/corrections cache BOARD  is a separate SoC that serves as the interface  42  ( FIG. 1 ) of the entire board. It is also connected to every SoC by the errors/corrections bus  7  for the board, as well as error-alert pins  6   a ,  6   b  from each SoC. 
         [0107]    One chassis contains several boards and other subsystems- monitor, printer, hard disk, etc. Each board has its errors/corrections cache BOARD  serving as an interface  42  ( FIG. 1 ) connected to a chassis-level errors/corrections cache cluster, errors/corrections cache CHASSIS    12 . Other subsystems  9  of the chassis also must be provided with interfaces  10  that are connected by error-alert pins  11 a, lib and the chassis errors/corrections bus  13  to the errors/corrections cache CHASSIS    12 , analogouosly to the boards. 
         [0108]    A further extension or refinement of the hierarchy applies to a group of chassis that again in turn has an errors/corrections cache GROUP . The latter in turn is connected by an errors/corrections bus  14  of the chassis group and by individual error-alert pins  15  to all errors/correction cache CHASSIS  modules  12 . 
         [0109]    A still-further refinement to a network of chassis groups is the next step. In some cases the provision of an errors/corrections bus and individual error-alert pins may be more difficult, especially if the chassis groups are widely separated physically. 
         [0110]    Thus a hierarchical error-controlling system according to preferred embodiments of my invention has a nested kind of tiered structure. In this nested structure, each major element  2   a ,  5   a  or  8  in a given tier and of a certain type reports to and is controlled by a lower-level element  5   a ,  8  or  12  respectively, which is of that same certain type—but which controls a relatively large number (i. e., a plurality or preferably a multiplicity) of like major elements  2   b ,  5   b  or  10 , respectively, in the given tier. 
         [0111]    More specifically the certain type of element is in the nature of an errors/corrections cache  44  ( FIG. 1 ). In preferred embodiments of my hierarchical system, however, that element type also performs the function of an interface  42  module for one or more elements in a higher tier. 
         [0112]    The hierarchical system of my present invention has important advantages, as compared with the unit error-controlling architecture introduced in section 2 above. These advantages particularly include very significant increases in practicality and effectiveness. 
         [0113]    It will be understood that just one single errors/corrections cache  44  ( FIG. 1 ) can serve for an entire chassis, but for best performance it would require interface  42  connections to virtually every chip and other device on the chassis. That in turn would call for many error-alert pins, and a potential excess of messages waiting for access to the error/corrections bus  34 . 
         [0114]    Therefore a hierarchical structure is a more satisfactory solution. Again, each board has its own errors/corrections cache cluster, and all of those report to a chassis-level errors/corrections cache cluster  12  that watches for errors on all of the boards. 
         [0115]    The board errors/corrections cache cluster  8  performs the role of the interface  42  for the entire board, and obeys commands received from the chassis errors/corrections cache cluster. As indicated above, the hierarchy can be extended further, based upon the same rationale. 
         [0116]    My novel hierarchical system is especially effective and advantageous if incorporated into a single “System on Chip” or SoC that itself includes several relatively large blocks—processors, memories, etc. that all fit on one package. Therefore it makes sense to build in an error-controlling resilience support system for the SoC. 
         [0117]    As it is built in, the overall arrangement has to be done during design—it cannot be retrofitted. Every block now has an interface (like interface  42 ,  FIG. 1 ). 
         [0118]    The SoC adds a errors/corrections cache cluster (also designed as one SoC block) that serves as interface for the entire SoC chip, and that communicates to the board-level errors/corrections cache cluster  8 . The latter is most naturally a separate chip for the board. 
         [0119]    As a practical matter, error messages sent from the computing system to the hierarchical error-controlling system are of a sort that is very closely related to the kind of computing system in use, and its particular computing functions. Likewise the corrective responses returned from the hierarchical error-control system to the computing system depend very specifically on the character and functions of the computing system. 
         [0120]    Hence if the SoC is intended to be generic, and to have many signal lines for connection to the computing system after manufacture of the SoC, then preferably the SoC includes a RON or PROM section which can be filled (or “programmed”, so to speak) after manufacture of the rest of the SoC. This arrangement customizes the SoC to those computing functions and character or in other words supplies the particular error messages and corrective responses required by the computing system. 
         [0121]    My new hierarchical system is suitable for future commercial processors as well as other commercial chips. They should accordingly be provided with an interface module. 
         [0122]    For present commercial chips, unfortunately no error-controlling resilience support system is available. A hierarchical overall architecture nevertheless can be made available by providing an interface module—or group of modules—as a separate chip. 
       5. Application of the Hierarchical Error-Control System 
       [0123]    Such a refined hierarchical error-control support system is highly resilient and provides—as further embodiments of my invention—major complexes of equipment, over a broad range of applications. These equipment complexes function based upon error-detection, -correction and -containment assemblies which are thereby made extremely dependable. 
         [0124]    These embodiments of my invention are advanced beyond any practical major equipment complexes of the present day. This is true because the computing functions of all such conventional major apparatus complexes are vulnerable to errors that are essentially undetectable, and therefore uncontrollable. Such errors arise in catastrophic events ranging from natural disaster through simple malicious hacking to terrorist intervention. These forms of my invention are especially critical in cases where human lives depend on the continuous and correct operation of the incorporated computing system—together with its inturn incorporated, refined hierarchical resilience support system. 
         [0125]    Thus one embodiment of the invention is a manned spacecraft  103  ( FIG. 3 ) from Earth  101 , on a long mission  102  such as exploration of the planet Mars  104 . The craft  103  is a major apparatus or equipment complex. Incorporated into the craft  103  of my invention is a computing system  105  which controls functioning of the craft, and which in turn includes (or has associated) a refined hierarchical error-controlling assembly  110 —according to my present invention—that protects the computing system  105 . 
         [0126]    Another embodiment of the invention is the protected computing system  105 , together with the associated or included hierarchical assembly  110 . Yet another embodiment is the hierarchical assembly  110  itself. Another embodiment of my invention is a human habitat  106  ( FIG. 4 ) to be located on a planet  104 , e. g. Mars, and including a computing system  107 , which in turn has associated—or includes—the hierarchical assembly  110  of my present invention. Such a human habitat  106  is a major equipment or apparatus complex according to my invention. As will be understood, earthbound complexes such as skyscrapers, energy-generation facilities, and scientific research centers if protected by my novel hierarchical assembly  110  are likewise embodiments of my invention. 
         [0127]    Still another embodiment of my invention is the included (and protected) computing system  107  that operates the habitat  106  or other major complex. Yet another embodiment is the included or associated protective hierarchical assembly  110 . 
         [0128]    Perhaps much simpler but also critical embodiments of my invention are vehicles such as an ocean liner  108  ( FIG. 5 ) that incorporates a computing system  109  which controls the vehicle and is protected by the novel hierarchical assembly  110  of my present invention. Likewise other embodiments are other kinds of vehicles for the transportation of humans on Earth—such as automobiles, airplanes and railroad trains. Further embodiments of my invention include the computing system  109 , as well as the hierarchical assembly  110  itself. 
         [0129]    At a smaller physical scale are other important types of hierarchical-assembly-protected apparatus including commodity computing systems such as a server or a desktop personal computer PC ( FIG. 6 ). Such a computer PC, which is an embodiment of my invention, includes or has associated a hierarchical assembly  110 . 
         [0130]    In certain of the appended apparatus claims, the term “such” is used (instead of “said” or “the”) in the bodies of the claims, when reciting elements of the claimed invention, for referring back to features which are introduced in preamble as part of the context or environment of the claimed invention. The purpose of this convention is to aid in more distinctly and emphatically pointing out which features are elements of the claimed invention, and which are parts of its context—and thereby to more particularly claim the invention. 
         [0131]    The foregoing disclosures are intended to be merely exemplary, and not to control the scope of my invention—which is defined by the appended claims 
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