Abstract:
An “ownership tag” in a special area of memory of a computer system identifies an owner of the computer system by displaying the ownership tag during initialization of the computer system. The ownership tag may be presented during the installation and execution of the Basic Input Output System (BIOS) preferably during Power on Self Test (POST) process. An administrator may access the ownership tag by interrupting the process by pressing the an appropriate key, which transitions the computer to an administrator set up mode. An administrator able to enter the administrator password may then alter the contents of the protected memory, changing the ownership tag. The ownership tag is preferably stored in a region of memory not accessible to a typical user, but accessible to an administrator aware of the administrator password. The ownership tag is stored in a flash memory, which is very difficult to remove from the system board, or to modify without administrator-level security access. This makes it superior to conventional storage mechanisms such as RTC RPM, hard disk, etc. since these are easily modifiable and/or easily removable.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to system level computer operation, and more specifically, to security measures to protect computer systems. 
     2. Description of the Related Art 
     As the computer industry has evolved, computers have become smaller and more portable. Reductions in size, power and other considerations, as well as diminution of chip size and migration of multi-chip functionality to a single chip have resulted in computers that are light weight, easy to use, and easy to transport. Given the highly mobile nature of portable computers and their usage, the trend toward more portable computer systems is likely to accelerate. 
     While the increased portability of small computer systems has generated tremendous advantages for the computer industry as well as for computer users, the risk of lost or stolen computer systems presents a continuing problem. Often without malicious intent, computer users inadvertently pick up a computer system belonging to another person or company. Moreover, even within the computer industry, employees often take small computers home in the evening or on weekends to work. Inevitably, problems arise as to the proper custody or ownership of a particular computer system. 
     Such problems do not only exist between separate entities. Even within a company, each department may be allotted a particular group of computer systems, and computer systems from other departments may inadvertently be carried into the area. Confusion may arise as to which computers belong to which area. 
     In addition to loss or theft of the physical computer system, intellectual property issues can also become implicated. Proprietary information loaded onto a computer system can be difficult to remove completely since various traces of deleted information often remain on a hard disk. When computer systems are indistinguishable, it may be difficult to insure that such information has been properly deleted from a computer system. Computer systems that have previously stored highly sensitive information may inadvertently fall into the hands of those not cleared for the information, perhaps jeopardizing confidentiality. 
     Physically marking a computer system, for example by engraving or otherwise marking the exterior of the computer case, has significant disadvantages. With respect to the innocent switching of computer systems, permanently marking the exterior of a computer case can make computer systems very difficult to reallocate. Because the needs for computers within a company can evolve over time, companies must be free to reallocate computers among various departments as needs arise. Therefore, permanently marking computer systems may be disadvantageous. With respect to the malicious theft of computer systems, permanently marking the exterior of a computer case does not prevent a thief from merely covering the exterior marking, or from replacing the computer case with another computer case and attempting to resell the computer. Therefore, the difficulties inherent in computer system identification are not solved by marking the case or cover. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention provides a new and improved identification technique for computer system. The present invention allows a computer administrator or other trusted person to place a “ownership tag” in a special area of memory that cannot be altered without the use of a special administrator password. The ownership tag indicates the person or entity who presently has the right of custody of the computer system. When a user powers on the computer system, the ownership tag is presented to the user. For example, the ownership tag is preferably presented during the installation and execution of the Power on Self Test (POST) portion of the Basic Input Output System or BIOS. 
     With the present invention, the POST processes can be interrupted. The POST process are interrupted by a user pressing a suitable key during the normal POST routine. Interruption of the POST process allows the computer to enter an administrator set up mode. In the administrator set up mode, a system administrator may enter the administrator password and alter the contents of the protected memory, changing the ownership tag. Additionally, the system administrator can if desired alter the ownership tag remotely over a network. 
     According to the present invention, the administrator may enter a special administrator password in order to alter the ownership tag. If desired, the computer system may be set so that a person must physically remove the memory device containing the ownership tag, place the ownership tag memory in an external device that is not part of the computer system, and apply external voltages and currents not available within the computer system to the memory in order to change the ownership tag. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which: 
     FIG. 1 is a schematic block diagram of a computer system according to the present invention. 
     FIG. 2 is a schematic diagram of flash ROM components of the computer system of FIG.  1 . 
     FIG. 3 is a schematic diagram of a video card and portions of the audio card of the computer system of FIG.  1 . 
     FIG. 4 is a block diagram of components initialized by a boot block in the computer system of FIG.  1 . 
     FIG. 5 is a schematic diagram of components of the computer system of FIG. 1 having multiple slots for connecting memory devices. 
     FIG. 6 is a flow chart of POST execution according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following disclosures are hereby incorporated by reference: 
     U.S. application Ser. No. 09/071,127, entitled “A COMPUTER METHOD AND APPARATUS TO FORCE BOOT BLOCK RECOVERY,” by Don R. James, Jr., Randall L. Hess, and Jell D. Kane, filed Apr. 30, 1998, U.S. Pat. No. 6,363,492, issued Mar. 26, 2002; 
     U.S. application Ser. No. 09/070,821, entitled “BOOT BLOCK SUPPORT FOR ATAPI REMOVABLE MEDIA DEVICES,” by Paul J. Broyles III, and Don R. James, Jr., filed Apr. 30, 1998, abandoned; 
     U.S. application Ser. No. 09/070,475, entitled “SECURITY METHODOLOGY FOR DEVICES HAVING PLUG AND PLAY CAPABILITIES,” by Christopher E. Simonich and Robin T. Tran, filed Apr. 30, 1998, U.S. Pat. No. 6,301,665, issued Oct. 9, 2001; 
     U.S. application Ser. No. 09/070,942, entitled “METHOD AND APPARATUS FOR REMOTE ROM FLASHING AND SECURITY MANAGEMENT FOR A COMPUTER SYSTEM,” by Manuel Novoa, Paul H. McCann, Adrian Chrisan. and Wayne P. Sharum, filed Apr. 30, 1998, U.S. Pat. No. 6,223,284, issued Apr. 24, 2001; 
     U.S. application Ser. No. 09/070,866, entitled “A METHOD FOR FLASHING ESCD AND VARIABLES INTO A ROM,” by Mark A. Piwonka, Louis B. Hobson, Jeff D. Kane, and Randall L. Hess, filed Apr. 30, 1998, U.S. Pat. No. 6,073,206, issued Jun. 6, 2000; 
     U.S. application Ser. No. 08/684,413, entitled “FLASH ROM PROGRAMMING,” by Patrick R. Cooper, David J. Delide, and Hung Q. Le filed Jul. 19, 1996, U.S. Pat. No. 5,805,882, issued Sep. 8, 1998; 
     U.S. application Ser. No. 09/071,128, entitled “A UNIFIED PASSWORD PROMPT OF A COMPUTER SYSTEM,” by Michael D. Garrett, Randall L. Hess, Chi W. So, Mohammed Anwarmariz, filed Apr. 30, 1998, U.S. Pat. No. 6,397,337, issued May 28, 2002; 
     U.S. application Ser. No. 09/123,307, entitled “COMPUTER SYSTEM WITH POST SCREEN FORMAT CONFIGURABILITY, by Rahul Patel and Paul J. Broyles III, filed Apr. 12, 2001; and 
     U.S. application Ser. No. 09/123,672, entitled “METHOD FOR STORING BOARD REVISION,” by Paul J. Broyles III and Mark A. Piwonka, filed Jul. 28, 1998, U.S. Pat. No. 6,405,311, issued Jun. 11, 2002; all of which are assigned to the assignee of this invention. 
     Computer System Overview 
     Turning to FIG. 1, illustrated is a typical computer system S implemented according to the invention. While this system is illustrative of one embodiment, the techniques according to the invention can be implemented in a wide variety of systems. The computer system S in the illustrated embodiment is a PCI bus/ISA bus based machine, having a peripheral component interconnect (PCI) bus  10  and an industry standard architecture (ISA) bus  12 . The PCI bus  10  is controlled by PCI controller circuitry located within a memory/accelerated graphics port (AGP)/PCI controller  14 . This controller  14  (the “host bridge”) couples the PCI bus  10  to a processor socket  16  via a host bus, an AGP connector  18 , a memory subsystem  20 , and an AGP  22 . A second bridge circuit, a PCI/ISA bridge  24  (the “ISA bridge”) bridges between the PCI bus  10  and the ISA bus  12 . 
     The host bridge  14  in the disclosed embodiment is a 440LX Integrated Circuit by Intel Corporation, also known as the PCI AGP Controller (PAC). The ISA bridge  24  is a PIIX4, also by Intel Corporation. The host bridge  14  and ISA bridge  24  provide capabilities other than bridging between the processor socket  16  and the PCI bus  10 , and the PCI bus  10  and the ISA bus  12 . Specifically, the disclosed host bridge  14  includes interface circuitry for the AGP connector  18 , the memory subsystem  20 , and the AGP  22 . The ISA bridge  24  further includes an internal enhanced IDE controller for controlling up to four enhanced IDE drives  26 , and a universal serial bus (USB) controller for controlling USB ports  28 . 
     The host bridge  14  is preferably coupled to the processor socket  16 , which is preferably designed to receive a Pentium II processor module  30 , which in turn includes a microprocessor core  32  and a level two (L2) cache  34 . The processor socket  16  could be replaced with different processors other than the Pentium II without detracting from the spirit of the invention. 
     The host bridge  14 , when the Intel 440LX Host bridge is employed, supports extended data out (EDO) dynamic random access memory (DRAM) and synchronous DRAM (SDRAM), a 64/72-bit data path memory, a maximum memory capacity of one gigabyte, dual inline memory module (DIMM) presence detect, eight row address strobe (RAS) lines, error correcting code (ECC) with single and multiple bit error detection, read-around-write with host for PCI reads, and 3.3 volt DRAMs. The host bridge  14  support up to 66 megahertz DRAMs, whereas the processor socket  16  can support various integral and nonintegral multiples of that speed. 
     The ISA bridge  24  also includes enhanced power management. It supports a PCI bus at 30 or 33 megahertz and an ISA bus  12  at ¼ of the PCI bus frequency. PCI revision 2.1 is supported with both positive and subtractive decode. The standard personal computer input/output (I/O) functions are supported, including a dynamic memory access (DMA) controller, two 82C59 interrupt controllers, an 8254 timer, a real time clock (RTC) with a 256 byte complementary metal oxide semiconductor (CMOS) static RAM (SRAM), and chip selects for system read only memory (ROM), real time clock (RTC), keyboard controller, an external microcontroller, and two general purpose devices. The enhanced power management within the ISA bridge  24  includes full clock control, device management, suspend and resume logic, advanced configuration and power interface (ACPI), and system management bus (SMBus) control, which implement the inter-integrated circuit (I 2 C) protocol. 
     The PCI bus  10  couples a variety of devices that generally take advantage of a high speed data path. This includes a small computer system interface (SCSI) controller  26 , with both an internal port  38  and an external port  40 . In the disclosed embodiment, the SCSI controller  26  is a AIC-7860 SCSI controller. Also coupled to the PCI bus  10  is a network interface controller (NIC)  42 , which preferably supports the ThunderLan™ power management specification by Texas Instruments. The NIC  42  is coupled through a physical layer  44  and a filter  46  to an RJ-45 jack  48 , and through a filter  50  to a AUI jack  52 . 
     Between the PCI Bus  10  and the ISA Bus  12 , an ISA/PCI backplane  54  is provided which include a number of PCI and ISA slots. This allows ISA cards or PCI cards to be installed into the system for added functionality. 
     Further coupled to the ISA Bus  12  is an enhanced sound system chip (ESS)  56 , which provides sound management through an audio in port  58  and an audio out port  60 . The ISA bus  12  also couples the ISA bridge  24  to a Super I/O chip  62 , which in the disclosed embodiment is a National Semiconductor Corporation PC87307VUL device. This Super I/O chip  62  provides a variety of input/output functionality, including a parallel port  64 , an infrared port  66 , a keyboard controller for a keyboard  68 , a mouse port for a mouse port  70 , additional series ports  72 , and a floppy disk drive controller for a floppy disk drive  74 . These devices are coupled through connectors to the Super I/O  62 . 
     The ISA bus  12  is also coupled through bus transceivers  76  to a flash ROM  78 , which can include both basic input/output system (BIOS) code for execution by the processor  32 , as well as an additional code for execution by microcontrollers in a ROM-sharing arrangement. 
     The ISA bus  12  further couples the ISA bridge  24  to a security, power, ACPI, and miscellaneous application specific integrated circuit (ASIC)  80 , which provides a variety of miscellaneous functions for the system. The ASIC  80  includes security features, system power control, light emitting diode (LED) control, a PCI arbiter, remote wake up logic, system fan control, hood lock control, ACPI registers and support, system temperature control, and various glue logic. 
     Finally, a video display  82  can be coupled to the AGP connector  18  through an AGP master or video card  150  for display of data by the computer system S. The video display  82  displays video and graphics data provided by a video display process running on either the processor module  30  or another by a PCI device bus master or PCI bridge device bus master via host bridge  14 . Video or graphics data may be stored in main memory or in a supplementary or extension memory module. Again, a wide variety of systems could be used instead of the disclosed system S without detracting from the spirit of the invention. 
     According to the present invention, certain memory locations having additional protection from alteration, such as indicated at  202  in flash ROM  78 , contain an ownership tag. The ownership tag  40  stored identifies the owner or person presently authorized custody or allocation of computer system S. When processor module  30  is booted, a basic input output system (BIOS) is loaded and executed on processor module  30 . According to the present invention, the processor associated with the BIOS obtains the ownership tag from the protected area of memory and displays the ownership tag on display  82 . 
     The ownership tag display may be of any suitable form and content consistent with the amount of protected area of memory allocated for this purpose. The ownership tag, identifies the person or business unit or entity which is the presently authorized owner or custodian of the computer system S. The ownership tag may identify an individual person or business entity who is the owner of the computer system, or it may identify a section or group within a company which is the currently authorized custodian of the computer system. Again, the format in which the tag is displayed is selected by the authorized administrator, based in part on the amount of memory allocated for this purpose. 
     The Flash ROM Boot Block 
     Turning now to FIG. 2, a sector partitioning structure  200  of the flash ROM  78  in the disclosed embodiment is shown. However, while this diagram is illustrative of one embodiment, the techniques according to the invention can be implemented in a variety of embodiments and can be implemented with a variety of non-volatile memory. The sector partitioning structure  200  is determined by the sector architecture of the particular flash ROM  78 . The flash ROM  78  used in the disclosed embodiment is an Advanced Micro Devices (AMD) AM29F002 type flash ROM memory. The sector partitioning structure  200  shows a top boot block design architecture. The Advanced Micro Devices AM29F002 flash ROM memory can also be implemented with a bottom boot block design architecture. 
     A boot block sector  202  consists of a first boot block sector  204  of 16 kilobytes and a second boot block sector  206  of 8 kilobytes. The remaining 232 kilobytes form a system block  208  divided into 5 sectors  210 - 218 . In the disclosed embodiment, the first sector  210  has 8 kilobytes, the second sector  212  has 32 kilobytes, and the remaining three sectors  214 ,  216 , and  218  have 64 kilobytes equally. 
     The code stored in the system block  208  preferably contains the Basic Input/Output System (BIOS) code. The BIOS is code interfacing between the operating system and the specific hardware configuration, allowing the same operating system to be used with different hardware configurations. The boot block  202  contains the code necessary to initialize the systems when an anomaly during power-up is detected. During a boot block  202  initialization, preferably a reduced set of hardware is initialized, thus reducing the size of the code in the boot block  202 . The boot block  202  code typically contains an initialization procedure for only the hardware necessary to perform limited functions. Typically a limited function necessary to be performed during boot block  202  initialization is the flash of the ROM  78 . 
     The boot block  202 , according to the invention, contains code initializing the hardware components necessary to flash the ROM  78  and to prompt the user for an administrative password. The boot block  202  code is contained within the boot block  202 , which is protected from spurious initialization. 
     The boot block  202  is stored in a region or protected area of memory not available to the user. Such a protected area may, if desired, be a flash memory which must be physically removed to be reprogrammed. A person must physically remove the boot block  202  and place that memory device in an external device to the computer system to reprogram it. Further, such a memory device is preferably one which for reprogramming requires voltage or current devices not available within the computer system S. 
     The system block  208  is electronically protected, but the system S is at least physically capable of disabling that protection and overwriting the system block  208 . During a flash, the system block  208  sectors may be rewritten with a new flash ROM image. 
     The flash ROM  78  is a 256 KB ROM that also supports a 24 KB boot block. The flash ROM  78 , upon system initialization, creates a ROM image in RAM when the ROM image becomes corrupted or otherwise unsatisfactory. The flash ROM  78  uses nonvolatile (NV) RAM to check the image and to determine whether the ROM image, stored in RAM is valid. If the image is bad, the ROM boots from the boot block rather than from the image. The NVRAM and ROM contain logic to select a memory subsystem mode, such as factory mode, normal mode, and administrator mode. Depending on the level of security required, different information stored may be stored in this memory for display at selected times during operation of the computer system S. With the present invention, the ownership tag is protected at an administrator mode level. 
     The boot block  202  contains an additional portion of ROM code within the ROM  78  that is executed at system reset. The boot block code contains a validation portion and a boot portion. Upon system reset, the validation portion performs a validation check on the system ROM  78  itself and either jumps to the normal system ROM code or to the boot portion, depending upon the result of a validation check. The boot portion, although not capable of initializing any add-in devices except IDE&#39;s, does contain enough code to allow a system administrator to flash a valid ROM code into ROM  78  from a diskette. The boot block is physically located within the ROM to be accessed by the reset vector. 
     The flash ROM  78  as has been mentioned, may be an AMD29F002T, which contains a 16 KB sector, two 8 KB sectors, a 32 KB sector, and three 64 KB sectors. The boot block occupies the first two sectors (totaling 24 KB), and is followed by an 8 KB ESCD sector, a reserved 32 KB sectors, a 64 KB sector containing normal-mode ROM code, 64 KB of compressed data, and 64 KB of CPU BIOS update code. The boot block  202  code typically is small in relation to the system block  208  code. According to the present invention, the ownership tag is stored in an administrator password protected area of flash ROM. 
     In the preferred embodiment, the memory sector with the ownership tag is not protected by the boot block hardware. Rather, the ownership tag is in a different sector of the flash ROM  78 , one which is protectable by administrator password. This is described below. 
     Turning to FIG. 3, a schematic diagram of a typical AGP master or video card  150  and portions of the audio card  154  (FIGS. 1 and 3) of the computer system S is shown. The inputs to the video card  150  include three composite video signals provided through Y 1 C video connectors, composite_ 1   302 , composite_ 2   304 , and composite_ 3   306 . The constituent signals of the three input composite signals are provided to a pair of video multiplexers  308  and  310 . A chrominance signal on line  312  from the composite_ 1  signal  302  is provided to video multiplexer  310 , and a luminance signal on line  314  of the composite_ 1  signal  302  is provided to video multiplexer  310 . The chrominance signal on line  316  of the composite_ 2  signal  304  is provided to video multiplexer  308 , and a luminance signal on line  318  of the composite_ 2  signal is provided to video multiplexer  310 . The composites_ 3  signal  306  includes a luminance signal on line  320  which is provided to video multiplexer  308 . Tuners  322  and  324  located on the audio card  154  of the computer system S also provide input luminance signals on lines  328  and  330  to video multiplexer  310 . Other conventional devices that are provided on the audio card  154  are not shown as the audio card  154  as they are not critical to an understanding of the present invention. 
     A signal on line  332  outputted from video multiplexer  308  is provided to a primary analog video multiplexer  334 . Video multiplexer  308  also provides a Y/C signal on line  336  to a secondary analog video multiplexer  338 . Video multiplexer  310  provides signals on lines  340  and  342 ; the signal on line  342  is provided to the primary analog video multiplexer  334 , and the signal on the other line  340  is provided to the secondary analog video multiplexer  338 . The analog video multiplexer  334  is integrated into a primary video composite decoder  344 , and the secondary analog video multiplexer  338  is integrated into a secondary video composite decoder  346 . The primary decoder  344  of the present invention may or may not include color separation circuitry, as desired. 
     The video card  150  of the computer system  10  of the present invention includes color separation circuitry  348  external to the primary decoder  344 . The color separation circuitry  348  receives a composite signal on line  350  as an input from video multiplexer  308  and outputs a chrominance signal on line  352  and a luminance signal on line  354  to the primary analog video multiplexer  334  of the primary decoder  344 . The color separation circuitry  348  includes a digital comb filter, by which video information is converted from analog to digital and back to analog. The video signal from decoder  344  is provided on line  358  a digital video multiplexer  360 . Similarly, an output video signal on line  262  of the secondary video composite decoder  346  is provided to a digital video multiplexer  364 . 
     The primary digital video multiplexer  360  provides two outputs, on lines  266  and  268 . The output on line  266  is provided directly to the VGA subsystem  370 . The output on line  268  is directed to a phase-locked-loop  372  (PLL). The PLL  372  supplies a clock signal on line  324  to the VGA subsystem  370 . The VGA subsystem  370  has two memory areas; one area is used as an off-screen memory area for storing video information, such as font information and data yet to be displayed. The other memory area of VGA subsystem  370  is used to store data which is currently being displayed. The VGA subsystem  370  also includes a VGA controller. In displaying data, the VGA controller reads from the off-screen memory, scales the data if needed, performs color space conversion, and then sends the data through a digital-to-analog converter (DAC) to the display. 
     In the secondary path, the secondary digital video multiplexer  364  provides a signal on line  276  to a video scaler and PCI bus interface  378 . When data is sent over the secondary path, the data is downscaled if needed and then burst over the PCI bus  120  into the off-screen memory area of the video memory. The secondary path is typically used for picture-in-picture (PIP) functionality or pulling up web pages while watching television on the display  82  which are encoded in the vertical blanket interval (VBI). 
     Therefore, typically, the video display device  82  is a primary output device that cannot be turned off during the BIOS. The display screen  82  is always active, and is always capable of presenting an image provided to it. Various peripheral devices can attempt to control the video display during the BIOS, since the operating system has not been loaded and launched and thus cannot control the peripherals. 
     Turning to FIG. 4, illustrated is a block diagram  400  of components of the system S that are initialized by the boot block  202 . The processor  32  copies the system block code  208  from the ROM  78  into RAM, creating the ROM image, and then executes the system block  208  code, including the boot block  202  code contained in the ROM image. The processor  32 , during initial power up and execution of boot block  202  code, executes the validation portion to determine if the flash ROM  78  has become corrupt. If the flash ROM  78  is corrupt, then the processor  32  executes the boot portion of the boot block to allow an administrator to re-flash portions of the boot block  202  code from a diskette. Also, during initial power up, when reflashing is not needed, the Super I/O device  62  and the security device  80  are initialized by the processor  32 . BIOS code is also loaded from the ROM or NVRAM into RAM. 
     Whichever boot code the validation portion determines to use is loaded into NVRAM (nonvolatile memory) within the black box or security device  80  (FIGS.  1  and  5 ). The NVRAM is faster than the ROM itself. When power is applied to the system, the BIOS is booted from the ROM, either via the image or the NVRAM. The BIOS then attempts to complete system initialization in normal mode unless interrupted during initialization. BIOS execution continues from the NVRAM and, upon conclusion, launches the operating system. The NVRAM and black box may also reside in a dedicated chip or device, or may reside in the Super I/O  62 . 
     The NV RAM Black Box 
     Turning now to FIG. 5, black box or security device  80  and NV RAM of the super I/O chip  62  are shown in greater detail. The black box  20  is nonvolatile RAM (NVRAM) that is composed of CMOS, yet is accessible only to the BIOS and the operating system (not to any other software running on the computer system). An unauthorized user, or one not possessing the appropriate administrative password, cannot access the location of the CMOS containing the ownership tag. The black box is a protected region within the NVRAM that is writeable only by the BIOS, and readable only by the BIOS and by the operating system. NVRAM is typically provided with back-up batteries to prevent power loss. The BIOS accesses the CMOS by generating an Int 15 h followed by the location within CMOS and, if the access is write enabled, data to be written to the CMOS location. This process is described below with respect to boot access to the ownership tag. 
     The memory security device  80  of FIG. 5 functions to lock and unlock resources within the computer system S, having multiple slots for connecting memory devices. The memory security device  80  of FIG. 4 includes three slots, numbered  0  through  2 , each protected according to a different methodology. The contents of the memory devices connected to each security device  80  are accessible only to memory access requests complying with the corresponding methodology. Each slot of device  80  has two states: a locked state, in which data is protected, and an unlocked state. In the locked state, access is denied to the memory device connected to the corresponding slot. To transition to the locked state, a user must enter a “protect resources” command. To transition to unlocked state, transitioning the slot from the locked state, an “access resources” command must be issued, followed by a correct password. 
     Slot  0  of device  80  includes a flash ROM interface connecting to a flash ROM device, such as flash ROM  78 . Slot  0  is the factory made protection level. It protects the flash ROM  78  from unauthorized writes such as viruses and unauthorized individuals. At power-up, the BIOS loads a flash ROM password into slot  0  and executes the “protect resources” command for that slot. After the system S has completed the boot process and before any other software is loaded, the BIOS issues a “protect resources” command to slot  0 , disabling further access to the flash ROM  78 . 
     Slot  1  of device  80  contains the “power-on” password of the user. The security device  80  communicates with the super I/O chip  62  containing the CMOS, by holding an “SIOAEN” and/or a “SIOWCL” signal to keep the super I/O chip  62  from decoding read and/or write cycles to the “power-on” password locations in the CMOS. The AEN signal is derived from ANDing a signal indicating that the black box slot  1  is locked and a signal indicating that the last data write to a real time clock index register was in the “power-on” password range, indicating that the user has missed an opportunity to access the “power-on” password location. Thus, the security device  80  controls access to the CMOS within the super I/O chip  62 . The slot  1  of the black box selectively disables access to the “power on” password storage area  502  within the CMOS. In contrast, the SIOWCL signal operates similarly to the SIOAEN signal, although the SIOWCL signal only prohibits writes and does not prohibit reads to the password. Thus, the SIOWCL signal may be used during subsequent user sessions to determine whether the user password has been entered correctly. 
     Slot  2  of the security device  80  is accessible only with an administrator password. The limited access of the slot  2  memory device protects system resource information that must be protected to preserve the integrity of the computer system. The administrator password is necessary to access particular registers of CMOS region  504 . As has been noted, the ownership tag of the computer system S according to the present invention is stored in region  504 . The unlocking of slot  2 , however, also unlocks slot  1 , allowing an administrator cognizant of the administrator password to access these CMOS locations. Thus, the administrator has control of these memory locations in the computer system. It is recommended that, prior to unlocking slot  2 , the administrator check the status of slot  1  to see if it is locked, since relocking slot  2  does not re-lock slot  1 . 
     The ownership tag can also be secured without the black box  80 . In some implementations, the black box  80  can be used to store the ownership tag and increase the security level. However, this is not required. As has been noted, the ownership tag is protected as a minimum normally by administrator password. 
     According to the present invention, the ownership tag is preferably displayed during the POST routine for the computer system S. FIG. 6 in the drawings illustrates a flow chart of those steps which accomplish he display of the ownership tag on the display  82 . As will be noted, the ownership tag may be displayed as a routine portion of the normal POST routine, or alternatively may be changed by an authorized administrator and then subsequently displayed. The remaining portions of the POST process are conventional and are depicted, for example, in co-pending U.S. application Ser. No. 09/123,307, “COMPUTER SYSTEM WITH POST SCREEN FORMAT CONFIGURABILITY,” filed Apr. 12, 2001. 
     During the conventional POST process, a step  600  occurs when the error interrupts and interrupts from the keyboard  68  are enabled. At this point the display of the ownership tag according to the present invention occurs Normally, a step  602  assumes operation of the computer system S during the POST process and causes the ownership tag to be transferred from location  202  in the flash ROM  78  and transferred into a suitable RAM memory location in the computer system S. Thereafter, during step  604 , the ownership tag is transferred from the RAM memory location into a video buffer in the video card  150  during a step  604 . Thereafter, during step  606 , the ownership tag contained in the video buffer is displayed on the display  82  during a step  606 , from which control of the computer system S reverts back to the remaining portions of the conventional POST process described in the co-pending application mentioned above. 
     This is done by a user depressing a suitable key, generating a keyboard interrupt during step  610 . Thereafter, during a step  612 , the computer system S prompts the user for the administrator password required for access to slot  2  of the security device  80  in order to access region  504  of CMOS memory containing the administrator password. If the proper administrator password is received, the ownership tag stored in slot  2  of the security device  80  may be modified during a step  614 . If an improper password is attempted during step  612 , access to the slot  2  of the security device  80  is prohibited. After the ownership tag is received during step  614 , control of the computer system S transfers to step  602  and display operations continue in the manner previously described. 
     An example code for retrieving and displaying the ownership tag according to the present invention is set forth below: 
     
       
         
               
               
             
               
               
               
             
               
               
             
               
               
               
               
             
               
               
               
             
               
               
               
               
             
               
               
             
               
             
               
               
               
             
               
               
             
               
             
               
               
               
               
             
               
             
               
               
             
               
               
               
             
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
               
               
             
               
               
               
               
             
               
             
               
               
               
             
               
             
               
               
             
               
               
               
               
             
               
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
               
               
               
             
               
             
               
               
               
             
               
             
           
               
                   
                   
               
             
             
               
                   
                 dpaintOwnershipTag - Draws the ownership tag onto clean screen. 
               
             
          
           
               
                   
                 Entry: 
                 None 
               
               
                   
                 Exit: 
                 Ownership tag is visible on the clean screen. 
               
               
                   
                 Regs: 
                 Flags 
               
             
          
           
               
                   
                 dPaintOwnershipTag proc near 
               
             
          
           
               
                   
                 push 
                 dx 
                   
               
               
                   
                 push 
                 bx 
               
               
                   
                 mov 
                 dh,COWNERTAG_ROW 
                 ; DH = Row to display string 
               
             
          
           
               
                   
                 mov 
                 bx, (CSCREEN_PAGE SHL 8) OR COWNERTAG_ATTR 
               
             
          
           
               
                   
                   
                   
                 ; Page 3, Attribute=70h 
               
               
                   
                 call 
                 dWriteOTString 
                 ; Write the string. 
               
               
                   
                 pop 
                 bx 
               
               
                   
                 pop 
                 dx 
               
               
                   
                 ret 
                   
                 ; return to caller 
               
             
          
           
               
                   
                 dPaintOwnershipTag endp 
               
               
                   
                 **************************************************************************** 
               
               
                   
                 DisplayOwnershipTag - This routine puts the Ownership tag on the normal (verbose) boot 
               
             
          
           
               
                 screen. 
               
             
          
           
               
                   
                 Entry: 
                 None 
               
               
                   
                 Exit: 
                 String is displayed. 
               
               
                   
                 Regs: 
                 flags. 
               
             
          
           
               
                   
                 Notes: This routine is called to display the normal string as well as the “clean boot” string. 
               
               
                   
                 ------------------------------------------------------------------------------------------------------------------- 
               
             
          
           
               
                 DisplayOwnershipTag proc near 
               
             
          
           
               
                   
                 push 
                 dx 
                   
               
               
                   
                 push 
                 bx 
               
               
                   
                 mov 
                 dh,OWNERTAG_ROW 
                 ; DH = Row to display string. 
               
               
                   
                 mov 
                 bx,(NSCREEN_PAGE SHL 8) 
                 + OWNERTAG_ATTR 
               
               
                   
                   
                   
                 ; Page 0, Attribute=07h 
               
               
                   
                 call 
                 dWriteOTString 
                 ; Write the string. 
               
               
                   
                 pop 
                 bx 
               
               
                   
                 pop 
                 dx 
               
               
                   
                 ret 
                   
                 ; return to caller 
               
             
          
           
               
                 DisplayOwnershipTag endp 
               
               
                 ***************************************************************************** 
               
             
          
           
               
                   
                 dWriteOTString - This routine pumps the ownership tag out onto the screen. 
               
             
          
           
               
                   
                 Entry: 
                 BL = Text attribute for string. 
               
               
                   
                   
                 BH = Video page # to write to. 
               
               
                   
                   
                 DH = Row to write string to. 
               
               
                   
                 Exit: 
                 If user has set a string, it will be displayed. 
               
               
                   
                 Regs: 
                 flags. 
               
             
          
           
               
                   
                 Notes: This routine is called to display the normal string as well as the “clean boot” string. 
               
               
                   
                 ---------------------------------------------------------------------------------------------------------------- 
               
             
          
           
               
                 dWriteOTString proc near 
               
             
          
           
               
                   
                 push 
                 es 
                   
               
               
                   
                 push 
                 ds 
               
               
                   
                 pusha 
               
               
                   
                 push 
                 dx 
                 ;) Save entry parameters. 
               
               
                   
                 push 
                 bx 
                 ;) 
               
               
                   
                   
                   
                 ; Get Ownership Tag into DS:SI 
               
               
                   
                   
                   
                 ; ------------------------------- 
               
               
                   
                 mov 
                 ax,0E845h 
                 ; AX=E845=”Get/Set NVS Features” 
               
               
                   
                 xor 
                 bx, bx 
                 ; DL=0=”Read NVS Feature” 
               
               
                   
                 mox 
                 cx, 13h 
                 ; CX=13=”Read Ownership Tag” 
               
               
                   
                 push 
                 OT_SCRATCH_SEG 
                 ;)DS=Scratch segment 
               
               
                   
                 pop 
                 ds 
                 ;) 
               
               
                   
                 mov 
                 si.OT SCRATCH OFS 
                 ; SI = Scratch offset 
               
               
                   
                 int 
                 15h 
                 ; Go get it! 
               
               
                   
                 jc 
                 short pot_done 
                 ; If no ownership tag, get out. 
               
               
                   
                   
                   
                 ; Determine length of ownership tag 
               
               
                   
                   
                   
                 ; -------------------------------- 
               
               
                   
                 push 
                 ds 
                 ; )ES=DS 
               
               
                   
                 pop 
                 es 
                 ;) 
               
               
                   
                 mov 
                 di, si 
                 ; Go to end of string 
               
               
                   
                 mov 
                 cx, 80 
                 ; Scan max 80 characters 
               
               
                   
                 add 
                 di, cx 
                 ;) Start at end of string 
               
               
                   
                 dec 
                 di 
                 ;) 
               
               
                   
                 std 
                   
                 ; Scan backwards . . . 
               
               
                   
                 mov 
                 al, ′ ′ 
                 ; . . . for first non-space. 
               
               
                   
                 repe 
                 scasb 
                 ; Do it! 
               
               
                   
                 jz 
                 pot_done 
                 ; Y; ZF set=empty 
               
               
                   
                 inc 
                 cx 
                 ; Adjust CX for last scasb 
               
               
                   
                   
                   
                 ; DS,ES:SI=&amp;OwnerTag, CX=Length 
               
               
                   
                   
                   
                 ; Center and display string 
               
               
                   
                   
                   
                 ; -------------------------------- 
               
               
                   
                 mov 
                 bp,si 
                 ; BP=Offset of string 
               
               
                   
                 pop 
                 bx 
                 ; Restore page# and attribute 
               
               
                   
                 pop 
                 dx 
                 ;) Restore row to show string 
               
               
                   
                 push 
                 dx 
                 ;) Preserve stack integrity 
               
               
                   
                 push 
                 bx 
                 ;] 
               
               
                   
                 mov 
                 dl,80 
                 ; DL=# columns on screen 
               
               
                   
                 sub 
                 dl, cl 
                 ;) 
               
               
                   
                 shr 
                 dl, 1 
                 ;) DL = offset of centered string 
               
               
                   
                 mov 
                 ax, 01300h 
                 ; AX-“Write String, keep cursor” 
               
               
                   
                 int 
                 10h 
                 ; Write string! 
               
             
          
           
               
                 pot_done: 
               
             
          
           
               
                   
                 pop 
                 bx 
                 ;) Clean up stack 
               
               
                   
                 pop 
                 dx 
                 ;} 
               
               
                   
                 popa 
               
               
                   
                 pop 
                 ds 
               
               
                   
                 pop 
                 es 
               
               
                   
                 ret 
               
             
          
           
               
                 dWriteOTString endp 
               
               
                 ****************************************************************************** 
               
               
                 Read/Write the Ownership Tag. It is Administrator Password protected on writes. It resides in 
               
               
                 the ESCD sector of the ROM. 
               
               
                 NOTE: This is a code excerpt from a runtime service which is called by the ROM Setup Software 
               
               
                 to read and/or write the Ownership tag. It demonstrates the password protected nature of 
               
               
                 ownership tag, and shows how it is stored in a flash sector. 
               
               
                 Ownership Tag: 
               
             
          
           
               
                   
                 mov 
                 ex.OWNERSHIPTAG_LENGTH 
                 ; 
               
               
                   
                 call 
                 outline_on? 
                 ; Q;ESCD from RUNTIME seg 
               
               
                   
                 jz 
                 short ot runtime 
                 ; Y: Get it from runtime 
               
               
                   
                   
                   
                 ; N: Get it from post buffer 
               
               
                   
                 push 
                 es 
                 ; Save ES 
               
             
          
           
               
                   
                 mov 
                 edi,ESCD_WRITE_BUFFER+OWNERSHIP_TAG AND 0FFFFh 
               
               
                   
                 pushw 
                 ((ESCD_WRITE_BUFFER+OWNERSHIP_TAG) SHR 4) AND 0F000h 
               
             
          
           
               
                   
                 jmp 
                 short ot_common 
                 ; Join common code. 
               
             
          
           
               
                 ot_runtime; 
               
             
          
           
               
                   
                 mov 
                 edi,ESCD_RUNTIME_BUFFER+OWNERSHIP_TAG AND 0FFFFh 
               
             
          
           
               
                 Setup ES for real/virtual/protected-16 bit calls that use read/write ESCD 
               
             
          
           
               
                 setup_ES: 
                 ; Entry point to setup ES 
               
             
          
           
               
                   
                 push 
                 es 
                 ; Save ES 
               
               
                   
                 mov 
                 ax,cs 
                 ; Get CS 
               
               
                   
                 cmp 
                 ax,0F000h 
                 ; Q: Real or Virtual 85 mode? 
               
               
                   
                 jne 
                 ot_p16 
                 ;   no must be protected-16 
               
               
                   
                 push 
                 cs 
               
               
                   
                 jmp 
                 short ot_common 
                 ; real mode just use cs 
               
             
          
           
               
                 ot_p16; 
                 ; Protected-16 use ES they 
               
             
          
           
               
                   
                 push 
                 es 
                 ; passed in. ES-base 0F000h 
               
               
                   
                   
                   
                 ; limit 0FFFFh 
               
             
          
           
               
                 ot_common; 
               
             
          
           
               
                   
                 pop 
                 es 
                 ; ES = pointer to string data 
               
             
          
           
               
                 Read/Write the Variables/Strings stored in the ESCD sector of the ROM. 
               
             
          
           
               
                   
                 Input: 
                 ES:EDI 
                 := variable address in ESCD buffer 
               
               
                   
                   
                 CS:EBP 
                 := CMOSFeaturess2 table entry address 
               
               
                   
                   
                 ECX 
                 := string length 
               
               
                   
                   
                 BL 
                 := Read/Write flag 
               
               
                   
                   
                 DS:ESI 
                 := Read/Write buffer pointer 
               
             
          
           
               
                 ReadWriteESCDStrs: 
               
             
          
           
               
                   
                 or 
                 bl, b1 
                 ; Q: Reading? 
               
               
                   
                 jne 
                 short WriteESCDStr 
                 ;  N: go Write the ESCD String 
               
               
                   
                   
                   
                 ;  Y: return the ESCD String in DS:SI 
               
               
                   
                 test 
                 cs:[ebp+FFLAG],PWPROT_RD 
                 ; Q: Is Read Password Protected? 
               
               
                   
                 je 
                 short @f 
                 ;  N: continue 
               
               
                   
                   
                   
                 ;  Y: check Admin PW 
               
               
                   
                 call 
                 rwpd_test_admin_mode 
               
               
                   
                 stc 
                   
                 ; assume falure 
               
               
                   
                 jz 
                 short RWESCDStrsExit 
                 ;  N. done 
               
               
                   
                   
                   
                 ;  Y: continue 
               
             
          
           
               
                 @@: 
               
             
          
           
               
                   
                 mov 
                 al, es: [edi] 
                 ;transfer the bytes 
               
               
                   
                 inc 
                 edi 
                 ; 
               
               
                   
                 mov 
                 [esi], al 
                 ; 
               
               
                   
                 inc 
                 esi 
                 ; 
               
               
                   
                 loop 
                 @b 
                 ; next byte 
               
               
                   
                 clc 
                   
                 ; indicate success 
               
               
                   
                 jmp 
                 short RWESCDStrs Exit 
                 ; 
               
             
          
           
               
                 Transfer the new ESCD String to the ESCD buffer and then Flash the ROM via SMI. 
               
               
                 WriteESCDStr: 
               
             
          
           
               
                   
                 test 
                 ca; [ebp+FFLAG],PWPROT_WR 
                 ; Q: Is Write Password Protected? 
               
               
                   
                 je 
                 short @f 
                 ;  N: continue 
               
               
                   
                   
                   
                 ;  Y: check Admin PW 
               
               
                   
                 call 
                 rpwd_test_admin_mode 
               
               
                   
                 stc 
                   
                 ; assume falure 
               
               
                   
                 jz 
                 short RWESCDStrsExit 
                 ;  N: done 
               
               
                   
                   
                   
                 ;  Y: continue 
               
             
          
           
               
                 @@: 
               
             
          
           
               
                   
                 call 
                 hhwF000WriteEnable 
                 ; open up F0000h 
               
             
          
           
               
                 @@: 
               
             
          
           
               
                   
                 mov 
                 a1, [esi] 
                 ; transfer the bytes 
               
             
          
           
               
                   
                 inc 
                 esi 
                 ; 
               
               
                   
                 mov 
                 es;[edi], a1 
                 ; 
               
               
                   
                 inc 
                 edi 
                 ; 
               
               
                   
                 loop 
                 @b 
                 ; next byte 
               
               
                   
                 call 
                 hhwF000WriteProtect 
                 ; close F0000h 
               
               
                   
                 call 
                 UpdateFlashData_SMI 
                 ; go Flash the ESCD part of the ROM 
               
               
                   
                 clc 
                   
                 ; indicate success 
               
             
          
           
               
                 RWESCDStreExit: 
               
             
          
           
               
                   
                 pop 
                 es 
               
               
                   
                 ret 
               
             
          
           
               
                 ******************************************************************************** 
               
               
                   
               
             
          
         
       
     
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, materials, components, circuit elements, wiring connections and contacts, as well as in the details of the illustrated circuitry and construction and method of operation may be made without departing from the spirit of the invention.