IAQTPA
`US005204840A.
`.
`(11) Patent Number:
`5,204,840
`115)
`United States Patent
`Mazur
`[45] Date of Patent:
`Apr. 20, 1993
`
`
`(54) MEANS AND METHODS FOR PRESERVING
`MICROPROCESSOR MEMORY
`
`4,815,032
`3/1989 Fujii...cece. 364/900
`
`4,823,308 4/1989 Knight 00... 364/900
`4,897,631 1/1990 Jundt et alo wu... 365/228 X
`
`sveesee 365/222
`4,901,283
`2/1990 Hanbury et al.
`.
`
`4,959,774 9/1990 Davis 2... ceeceersecreseenees 364/200
`4,977,537 12/1990 Dias et al.
`365/228 X
`
`5,018,096 5/1991 Aoyama o..cccceccsseeecsceeen 364/900
`Primary Examiner—Alyssa H. Bowler
`[57]
`ABSTRACT
`Means and methods for preserving the RAM of an
`externally powered microprocessor on the occasion of a
`loss in external power. Whenthe powerloss is detected,
`a signal is generated whichinitiates a sequence to isolate
`the RAM and refresh it with an independent power
`supply. When main poweris restored, the microproces-
`sor is restored to its precise location at the moment of
`Powerloss. Shutdown,startup andsecurity routines are
`Provided by software embodied in the system.
`
`5 Claims, 4 Drawing Sheets
`
`[76]
`
`Inventor:
`
`(56)
`
`;
`Jeffrey G. Mazur, 8041 Sadring
`Ave., Canoga Park, Calif. 91304
`[21] Appl. No.: 391,096
`[22] Filed:
`Aug. 8, 1989
`[51] Unt. CLS ose GLIC 5/14; GO6F.12/14;
`[52] US. CM. cececcssssssssereseesesseeen 365/228; 365/229,
`395/425; 364/DIG. 1; 364/969.4; 364/DIG. 2
`[58] Field of Search..................... 364/200, 900, 969.4,
`364/969.3, 365/226, 227, 228, 229
`References Cited
`U.S. PATENT DOCUMENTS
`4,578,774
`3/1986 Muller .cccccscsescsteent 364/900
`
`4,631,701 12/1986 Kappeler etal. .....
`365/222 X
`
`4,718,038
`1/1988 Yoshida ...ccccccssccsscvvesseoee. 3647900
`4,788,661 11/198B Morita coscccssccscssesesessne 365/228 X
`
` 16
`
`
`5V Power Supply
`18
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`HP Exhibit 1005 - Page 1
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`HP Exhibit 1005 - Page 1
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`

`

`U.S. Patent
`
`Apr. 20, 1993
`
`Sheet 1 of 4
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`5,204,840
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`HP Exhibit 1005 - Page 2
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`HP Exhibit 1005 - Page 2
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`

`

`U.S. Patent
`
`Apr. 20, 1993
`
`Sheet 2 of 4
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`5,204,840
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`HP Exhibit 1005 - Page 3
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`HP Exhibit 1005 - Page 3
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`

`

`U.S. Patent
`
`Apr. 20, 1993
`
`Sheet 3 of 4
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`5,204,840
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`HP Exhibit 1005 - Page 4
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`HP Exhibit 1005 - Page 4
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`

`

`U.S. Patent
`
`Apr. 20, 1993
`
`Sheet 4 of 4
`
`5,204,840
`
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`HP Exhibit 1005 - Page 5
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`HP Exhibit 1005 - Page 5
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`
`
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`

`

`1
`
`5,204,840
`
`MEANS AND METHODSFOR PRESERVING
`MICROPROCESSOR MEMORY
`
`INTRODUCTION
`
`This invention relates generally to microcomputers
`and like devices which employ dedicated microproces-
`sors and moreparticularly to means and methods for
`maintaining the status quo of the microprocessor and all
`device memory associated therewith when the electric
`powersupplied thereto is either intentionally or unin-
`tentionally, diminished or is interrupted altogether.
`BACKGROUND OF THE INVENTION
`
`During the past ten to fifteen years microcomputers,
`and related devices have pervaded Western society and
`are commonplace throughout America. Indeed, it has
`been reported that one in seven American teenagers
`have access to their own microcomputer. The total
`number of microcomputers in use throughout
`the
`United States has been estimated to total more than 70
`million.
`Theproliferation of microcomputer devices has been
`fueled in large part by dramatic cost reductions in the
`manufacture of integrated circuit chips, namely Dy-
`namic Random Access Memory (DRAM)andin the
`production of Microprocessor (MPU) chips. Without
`low cost DRAM and MPUchips, the electronic explo-
`sion most likely would not have occurred.
`MPUand DRAMchips, andall devices reliant there-
`upon, share a common vulnerability. These chips re-
`quire a constant and uninterrupted supply of electric
`power to function properly. A power interruption of
`only a millisecond can cause such chipsto lose all infor-
`mation programmedthereon and thus abort what could
`be a very valuable asset of a business enterprise.
`The provision of uninterruptable power supplies to
`keep MPU and DRAMchipsin action at a time when
`an external power sourceis interrupted is not practical
`in most applications. Large batteries and complex
`switching are required which violate the basic size and
`weight requirements inherent in most applications uti-
`lizing MPU and DRAMchips.
`This vulnerability to imperceptible power outages
`affects not only the microcomputer, but those devices
`controlled or reliant upon MPU and/or DRAM chips.
`If, for example, a clothes or dishwasher is mechanically
`controlled, a five minute power outageis a minor incon-
`venience that the consumer may not even notice. When
`the power comes back on, the appliance continues with
`its cycle as if the interruption had not occurred.
`Such is not the case with the new and improved
`computer controlled appliances where the loss of
`powerto the DRAM and MPUassures thatall informa-
`tion kept therein is lost. In such a case, the appliance
`will go to the “ready”or “abort” mode, and await fresh
`input. The interrupted cycle will not be completed.
`Further, the programmed cycles maintained in DRAM
`and the MPUwill haveto be reestablished in the device
`before it can be again usefully employed.
`It is therefore apparent that a clear need exists for
`means and methods which will unequivocally preserve
`the information contained in DRAM and the micro-
`processor even though its power supply is interrupted
`and which will upon the restoration of the external
`powersource, allow the device with which the DRAM
`
`2
`and MPU are mounted to automatically restart its pro-
`cessing cycle at the precise point of interruption.
`BRIEF SUMMARYOF THE INVENTION
`
`At a system level, the meansof the present invention
`comprise both hardware and software. The hardware
`‘comprises in coactive combination a powerloss detec-
`tion circuit, an independent power supply, a continu-
`ously rechargeable battery which is recharged by the
`independent powersupply, a standby refresh circuit, a
`switch-over circuit, address and data busses, and an
`address control circuit, all of which are in addition to
`and augment the existing conventional computercir-
`cuits. The software used in combination with the hard-
`ware is capable, upon powerfail detect, to copy all of
`the volatile data stored in the microprocessor and de-
`liver it to nonvolatile storage. Upon subsequent power-
`up, the normal reboot sequence is aborted and the data
`held in the nonvolatile storage is copied back to the
`microprocessor which creates an “‘instant-on” system,
`that is, the user is returned to where heleft the machine
`when powerwas lost.
`In operation, the means and methods of the present
`invention back up the dynamic RAM memory of the
`associated computer system in the event of a powerloss
`or outage. In addition, the present invention preserves
`the status of the machine and upon resumption of the
`principal power source, restores the machine to the
`precise place it was at the momentof the powerloss or
`outage. Furthermore, means are provided which main-
`tain the security of the data and password protect the
`computer after restoration of original power.
`The prior art has heretofore dealt with the problems
`created for static random access memory (“SRAM”)
`when the power source fails. None have successfully
`transferred the protective concept to the management
`and protection of the dynamic RAM (DRAM).It is
`toward this goal that the present invention is directed.
`Accordingly a prime object of the present invention
`is to provide new and unique means and methods for
`placing a computer in “suspended animation” during
`the course of a loss or interruption of external power
`and for causing it to restart when the external poweris
`restored without any loss of information originally con-
`tained in DRAM orthe computer’s microprocessor.
`Another object of the present invention is to provide
`new and improved means which allow a microcom-
`puter to restart after a power interruption without re-
`quiring a reset or reboot process.
`A further object of the present invention is to provide
`new and improved means which allow a computerto be
`turned off and on, and to thereafter resume operation as
`if the powerinterruption had never occurred.
`These andstill further objects of the present inven-
`tion as shall hereinafter appear, are fulfilled by the pres-
`ent invention in a remarkably unexpected fashion as can
`be readily discerned from a careful consideration of the
`following description of the preferred embodiments
`thereof especially when read in conjunction with the
`accompanying drawing in which like parts bear like
`indicia throughout the several views.
`BRIEF DESCRIPTION OF THE DRAWING
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`In the drawing:
`FIG. 1 showsa functional block diagram of a system
`embodying the present invention;
`FIG. 2 is a more detailed block diagram of the em-
`bodiment of FIG. 1.
`
`HP Exhibit 1005 - Page 6
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`HP Exhibit 1005 - Page 6
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`

`

`3
`FIG. 3 is a block diagram of the power supply ofthe
`embodiment of FIG. 1; and
`FIG.4 is a block diagram of the powerfail detector
`of the embodimentof FIG. 1.
`
`5,204,840
`
`erasable
`
`4
`programmable ROM (“EE-
`
`electrically
`PROM”).
`Power supply means 18, as shownin FIG.3, includes
`an external transformer power source 30, rechargeable
`battery 31, battery charging circuit 32, and a voltage
`regulator 33. Charging circuit 32 acts continuously to
`recharge battery 31 so long as the hardware receives
`electricity from external power source 30. Power loss
`detection circuit 20, as shown in FIG. 4, comprises a
`precision reference voltage 34, an input voltage 35, and
`a comparator 36. When input voltage 35 falls below the
`value set for reference voltage 34, as determined by the
`comparator 36, a NMIsignal 37is sent to computer 16,
`to a delay 23, then to refresh switch-over circuit 24
`signifying the voltage drop. Delay 23 is an 1.C. circuit
`that delays the signal by about one millisecond. Such
`circuits are well known. Once refresh switch-over cir-
`cuit 24 has been notified of the voltage drop, circuit 24
`switches the DRAM of computer 16 to receive its
`DRAM refresh signal from refresh generator 22 rather
`than from within computer 16 (which signal was depen-
`dent on the power whose failure was detected). The
`refresh signals delivered by refresh generator 22 to the
`DRAM of computer 16 are synchronized to the com-
`puter’s normal refresh signal by a synchronization cir-
`cuit which is a part of refresh switch-over circuit 24.
`Refresh switch-over circuit 24 also acts to isolate the
`DRAMof the computer 16 from the computer device
`16 per se so that none ofthe information maintained and
`retained in the DRAM is corrupted during the shut
`downandrestart of computer 16. The refresh generator
`22 insures that the information in the DRAM is main-
`tained as it was at the last moment of normal operation
`of computer 16 so long as poweris received from power
`supply 18.
`Referring now to FIG. 2 which shows a block dia-
`gram of system 10 whenit is configured for use with a
`MACINTOSHSE computer (Apple Computer Corp.,
`Cuppertino, Calif.). Because the hardware must pre-
`cisely interact with the computer 16 on whichit is in-
`stalled, both software means 12 and the associated hard-
`ware will require some modification to render it com-
`patible with the device for which use of system 10 is
`intended. However,as will appear, the basic concept of
`the system as shownherein is equally applicable to all
`such computer devices with which the system 10 may
`be installed. The MACINTOSH SEis referred to
`herein merely to exemplify the invention.
`In one embodiment hereof, power supply means 18
`comprises an external
`transformer supply 30, a re-
`chargeable battery 31, a battery charging circuit 32, and
`voltage regulator 33. When the computer 16 is on, the
`voltage to system 10 and the DRAMis supplied by the
`computer’s internal power circuit. When the computer
`16 is turned off, unplugged, or otherwise loses its
`power, the requisite voltage to operate system 10 and
`refresh DRAM is instantaneously delivered by trans-
`former 30. Should transformer 30 lose power,
`the
`DRAM will forthwith receive its maintenance voltage
`from battery 31. Battery 31 is preferably nickel-cad-
`mium but any battery known to theart to be recharge-
`able can be used. The voltage delivered to system 10
`and the DRAMbyeither transformer supply 30 or
`battery 31 will be regulated through a voltage regulator
`33.
`As shown in FIG. 2, refresh generator 22 comprises
`an oscillator which produces pulses of a preselected
`
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`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`In practice, the means and methods embodying the
`present invention function as follows. When the power
`loss detection circuit senses a significant undervoltage
`from the external powersource relative to a preselected
`reference voltage value, the device hereof will automat-
`ically switch from a passive mode to an active mode and
`send a signal to the computer microprocessor directing
`it to follow a novel and unique shutdown routine with
`which it has been specifically programmed. After the
`microprocessor completes the shutdown routine, the
`microprocessoris essentially placed in suspended ani-
`mation. The typical gyrations followed by a micro-
`processor as it loses power do not affect the stored
`memory as the DRAM is isolated from the MPU
`switching circuitry. The states and pointers of the mi-
`croprocessor are recorded in a portion of the replace-
`ment DRAM which allows all of the information con-
`tained in the microprocessor and DRAM at the time of
`the powerloss to be preserved.
`The standby refresh circuit in the novel system will
`continue to refresh the replacement DRAM for the
`duration of the external power source interruption.
`Such interruption can persist for an indefinite period of
`time if the device is on external power. If both the de-
`vice and computer have lost power, the refresh can be
`continued for as long as its associated battery holdsout.
`Current batteries possess sufficient power to maintain
`the memoryin “suspended animation” for eight hours
`or more.
`When external poweris restored to the computer,the
`device embodying the present invention will direct the
`microprocessor to follow a special preprogrammed
`restart procedure and resume operating as if the power
`interruption had never happened. All of the micro-
`processor states and pointers are restored to the status
`quo ante. Whenthe voltage equals the preselectedrefer-
`ence value, the microprocessor is reenabled, and the
`microcomputer resumes normal operations. To the user,
`the restart of the microcomputeris essentially instanta-
`neous after power has been restored.
`Referring to the drawing, a memory preserving sys-
`tem embodying the present invention, is identified by
`the general reference numeral 10. As shown in FIG.
`each system 10 comprises software means 12 associated
`with hardware means, each of which are more fully
`described below. System 10, when operable, is coac-
`tively connected to a computer 16 which may contain a
`microprocessing unit (“MPU”) or a full board proces-
`sor.
`The hardware hereof comprises independent power
`supply means 18, power-loss detection circuit 20, re-
`fresh generator 22, a refresh switch-over circuit 24, a
`power switch-over circuit 26, a non-volatile memory
`(“NVM”) 28, and memory connection means 29 con-
`nected to the dynamic RAM of computer 16, each of
`which operatively interact with each other and coact
`with software means 12 to allow the system 10 to per-
`form its intended function as will now be more fully
`described. The term “non-volatile memory” as used
`herein includes such known memory elementsas static
`RAM,erasable programmable ROM (“EPROM”) and
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`65
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`HP Exhibit 1005 - Page 7
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`HP Exhibit 1005 - Page 7
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`5,204,840
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`5
`repetition rate and duration to refresh the DRAM sup-
`ported by system 10.
`In installing system 20 into a microcomputer 16, for
`example, a MACINTOSHSE,the DRAMis removed
`from the computer and placed on an auxiliary circuit
`board (not shown) upon which system 10 is mounted.
`Typical installation involves conventional SIMM sock-
`ets whichfor all functions except column address select
`(“CAS”), row address select (“RAS”) and supply volt-
`age (Vcc), couple the computer generated signals to the
`DRAM. The CAS, RASand Vcc signals will originate
`with the computer 16 when the computer’s power sup-
`ply is functioning correctly and from system 10 when a
`powerlapse has occurred.
`A variety of schemes exist for storing the software 12
`within the system 10. For example, when a MACIN-
`TOSHSEisin its startup mode, it looks for a hook at
`address $F80000. NVM 28 of the system 10 is located at
`address $F80000 and up. A special program is executed
`to place a program in the NVM. The code contained
`therein interrupts the normal restart procedure for the
`MACINTOSHandthe software 12 substitutes itself for
`the normal restart routines. After restart
`is accom-
`plished, the software 12 allows the MACINTOSH to
`continue running the application software from the
`point of interruption.
`The code in the NVM also controls the power-fail
`routine.
`Synchronization means 38 in the refresh switch-over
`circuit 24 acts to synchronize refresh generator 22 with
`the refresh pulses generated by the MACINTOSH.
`This is necessary so that all DRAM are properly re-
`freshed when the system 10 is activated by powerloss
`detection circuit 20.
`In practice with MACINTOSHSE,a fall of the
`supply voltage below 4.8 V will be sensed by powerfail
`detection circuit 20 which activates a one shot delay
`generator to produce a six hundred micro second delay.
`If at the end of the delay, the incoming voltage to the
`computer 16is still below the precision reference volt-
`age 34, e.g., 4.8 V, as measured by loss detector 20, a
`non-maskable interrupt (“NMI”) signal
`is generated.
`The use of the micro second delay avoids false trigger-
`ing due to “glitches”. The NMIsignal then causes the
`shutdown portion of the software 12 to be run. The low
`voltage measurementalso activates refresh switch-over
`means circuit 24 via delay 23 to immediately direct
`refresh signals to the DRAM from the refresh generator
`22, circumventing the principal computer. The entire
`computer 16 is placed in suspended animation until such
`time as the computer supply voltage rises above the
`preselected precision voltage reference, e.g., 4.8 V, as
`measured by powerfail detection circuit 20.
`When the power supply to the computer 16 is re-
`stored, the computer 16 initiates the execution of the
`Start-up routine of software 12 and the refresh signals to
`the DRAM are again generated by the computer 16,
`instead of by refresh generator 22. The computer 16
`then begins to run the applications software at the exact
`place whereit left off when power went down.
`As appears above, the system 10 of the present inven-
`tion enables the Dynamic RAM ofthe computerto be
`saved even when the power supply voltage of the com-
`puter reaches 0. The system thus preserves all of the
`main memory of the computer as well as the internal
`memory of the microprocessor during the powerinter-
`ruption.
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`As previously explained, the software 12 can include
`four functional routines, namely, the installation pro-
`gram (or code), the shutdown routine (or code), the
`restart routine (or code) and the security routine (or
`code). These routines will now be described in further
`detail.
`Theinstallation program is run every time the com-
`puter is rebooted. This program installs the shutdown
`routine (or code) and the restart routine (or code) into
`the NVM 28 disposed on the system board 10. It also
`changes the NMI vector so that the vector now points
`to the shutdown code. As will appear, the restart code
`is installed in such a way that it is automatically exe-
`cuted upon restart of the computer. Note that in a per-
`fect world, the installation program will be run only
`once, because system 10 obviates the need to reboot the
`computer ever again.
`The second aspect of software 12 is the shutdown
`code. The computer’s NMIvectoris set to point to this
`code as explained above. Thus, when an NMIis re-
`ceived, the shutdown code is immediately executed.
`Upon execution, the code saves the contents of the
`registers in the MPU,saves the VIA registers, calcu-
`lates a checksum of a portion of memory, and then saves
`the checksum. This has the effect of saving the status of
`all volatile memory which had been in the computer
`(the DRAMis no longer volatile because of the opera-
`tion of system 10). The code then places a special “sig-
`nature” word on the stack to indicate thatit (the code)
`has been mn.
`Thethird aspect of software 12 is the restart code.
`Upon re-application of power, computer 16 starts to
`reboot. Early in the reboot code, it checks to see if there
`is a “magic” flag at location $F80000. If this flag is
`present, the code pointed to by the data at SF80004 is
`executed. Whentheinstallation program is run,it places
`the flag at $F80000, and the address of the restart code
`at $F80004. Becauseofthis, the restart code is executed
`whenever poweris restored. The restart code checks to
`see if the special signature word is present on the stack.
`If it is not, the code assumes that the user wants to
`reboot computer 16 and obligingly reboots the machine.
`However,if there is a special code or signature on the
`stack this will indicate that the computer was inter-
`rupted. In this case, rebooting will not occur. Instead,
`software 12 simply restores computer 16 to thestatus it
`was in when powerloss occurred. If a secret mode is
`implemented, then restoration is back into the middle of
`the security code. The code then re-calculates the mem-
`ory checksum and compares it with the saved value. If
`they are not equal, the machine is rebooted. The code
`then restores the registers of the MPU and VIA.This
`has the effect of restoring the computerto virtually its
`exact state at the moment the powerfailed.
`The fourth aspect of software 12 whichis optional,is
`the security code. The security code actually consists of
`two parts, namely, one which is a utility which allows
`the user to set a password to prevent unauthorized
`access to his machine. The password is encrypted and
`stored in SRAM 28 of system 10. This utility also allows
`the user to set a delay time to allow his hard drive to
`come up to speed.
`The secondpart of the security code is a desk acces-
`sory (DA) which activates the security feature. DA’s
`are programs which can be activated in the middle of
`another program. The DA in system 10 allows the user
`to turn off his computer with security activated. When
`poweris restored, the DA prevents access to the com-
`
`HP Exhibit 1005 - Page 8
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`HP Exhibit 1005 - Page 8
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`5,204,840
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`a voltage regulator, and a battery charging circuit
`puter until the correct password has been entered. At
`connected to said battery, said transformer power
`this time the screen is preferably blackened to prevent
`supply being connected to said voltage regulator
`unwanted observation. The programmer’s interrupt
`and to said battery charging circuit, said battery
`switch is disabled, and reset has been circumvented, so
`being connected to said voltage regulator for deliv-
`there is no way to access the computer without entering
`ery of powerto said switch-over circuit; and
`the correct password.
`a power-fall detection circuit comprising a precision
`In the preferred practice of the present invention,all
`voltage reference, means for measuring the input
`the circuitry herein described and illustrated in the
`description of system 10, with the exceptionofbatteries
`voltage to said computer system, and a comparator
`for initiating an NMIalert signal when said mea-
`31, can be mounted on a single circuit board whichis
`sured input voltagefalls below said precision volt-
`installable within computer 16 in the same manner as
`any auxiliary circuit board is currently installed. When
`age reference; and
`space constrictions do not allowasingle board, system
`software operatively associated therewith and re-
`10 can be disposed on a plurality of boards, the actual
`sponsive to said powerloss detection circuit signal
`placement and disposition of the several
`increments
`to initiate a shutdown routine when said signal ts
`being with the skill of the art and not material to the
`activated and to initiate a restart routine when said
`unique functioning of the described system.
`signal is deactivated; and
`From the foregoing,
`it becomes apparent that new
`security means for interrupting a normal startup se-
`and useful procedures have been herein described and
`quence of said computer system to invoke a secu-
`illustrated which fulfill all of the aforestated objectives
`rity procedure, whereby further use of said com-
`in a remarkably unexpected fashion. It is of course un-
`puter system would be allowed only after identify-
`derstood that such modifications, alterations and adap-
`ing an authorized user.
`tations as may readily occur to an artisan having the
`2. The system of claim 1 wherein said security means
`ordinary skills to which this invention pertains are in-
`includes a startup detection circuit which connects to
`tended within the spirit of the present invention which
`said computer system, which detects execution of the
`is limited only by the scope of the claims appended
`startup sequence and positively interrupts said startup
`hereto.
`sequence and instead executes a security routine.
`Accordingly, what is claimed is:
`3. The system of claim’2 wherein said security routine
`1. A system for preserving at least the main random
`comprises software operatively associated therewith
`access memory (“RAM”) of a computer system having
`and responsive to said startup detection circuit to initi-
`a power supply on the occasion of a sudden loss in
`ate a security routine when said startup sequence is
`power, said system comprising:
`detected and to allow the normal startup sequence to
`a powerloss detection circuit adapted to sense a loss
`proceed only after properly identifying an authorized
`in the power supply of said computer system and
`user.
`emit a signal causing a switch-overcircuit to isolate
`4. The system of claim 1 wherein said security means
`at least said main RAM from the computer system
`includes nonvolatile memory to store a security routine
`and cause at least said main RAM to receive its
`and/oruser identification information.
`power from an independent power source; and
`5. The system of claim 3 wherein said security means
`a power switch-over circuit responsive to said power
`includes hardware and/or software to operatively pre-
`loss detection signal to connect said independent
`vent any person from circumventing the function of the
`power source to said memory; and
`security means.
`an independent power supply comprising an external
`*
`*
`*
`*
`*
`transformer power supply, a rechargeable battery,
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`65
`
`HP Exhibit 1005 - Page 9
`
`HP Exhibit 1005 - Page 9
`
`