Hardware Prospection
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Dual-Mode Operation
An automatic transmission for an automotive vehicle includes a continually variable drive mechanism having one sheave assembly fixed to an intermediate shaft and the input sheave assembly supported on an input shaft, gearset driveably connected to the input shaft and an output shaft, a fixed ratio drive mechanism in the form of a chain drive providing a torque delivery path between the intermediate shaft and the carrier of the gearset, a transfer clutch for connecting and releasing the first sheave of the variable drive mechanism and input shaft, a low brake, and a reverse brake.
• Mode bit added to computer hardware to indicate the currentmode: monitor (0) or user (1).• When an interrupt or fault occurs hardware switches to monitormodeuser monitorinterrupt/faultset user mode• Privileged instructions can be issued only in monitor mode.
Sharing system resources requires operating system to ensurethat an incorrect program cannot cause other programs toexecute incorrectly.• Provide hardware support to differentiate between at least twomodes of operations.1. User mode – execution done on behalf of a user.2. Monitor mode (also supervisor mode or system mode) –execution done on behalf of operating system.
I/O Protection
• All I/O instructions are privileged instructions.• Must ensure that a user program could never gain control ofthe computer in monitor mode (i.e., a user program that, aspart of its execution, stores a new address in the interruptvector).
Memory Protection
• Must provide memory protection at least for the interrupt vectorand the interrupt service routines.• In order to have memory protection, add two registers thatdetermine the range of legal addresses a program may access:– base register – holds the smallest legal physical memoryaddress.– limit register – contains the size of the range.• Memory outside the deļ¬ned range is protected.
CPU Protection
The CPU protection feature enhances the efficiency of an HP device’s CPU and Content Addressable Memory (CAM). Some denial of service attacks make use of spoofed IP addresses. If the device must create CAM entries for a large number of spoofed IP addresses over a short period of time, it requires excessive CAM utilization. Similarly, if an improperly configured host on the network sends out a large number of packets that are normally processed by the CPU (for example, DNS requests), it requires excessive CPU utilization. The CPU protection feature allows you to configure the HP device to automatically take actions when thresholds related to high CPU or CAM usage are exceeded.
How the CPU Protection Feature Works The CPU protection feature uses the concepts of normal mode and exhausted mode. The device transitions from normal mode to exhausted mode when specified thresholds for conditions related to high CPU usage and CAM usage are exceeded. When the device enters exhausted mode, actions can be taken to reduce the strain on system resources. You can define the conditions that cause the device to enter exhausted mode, the actions to take while the device is in exhausted mode, and the conditions that enable the device to go back to normal mode. For example, you can specify that a CPU usage percentage of 90% is a condition that will cause the device to go from normal mode to exhausted mode. When the device enters exhausted mode, you can specify that the action to take is to forward unknown unicast traffic in hardware instead of sending it to the CPU. You can further specify that a CPU usage percentage of 80% will cause the device to go back to normal mode.
An automatic transmission for an automotive vehicle includes a continually variable drive mechanism having one sheave assembly fixed to an intermediate shaft and the input sheave assembly supported on an input shaft, gearset driveably connected to the input shaft and an output shaft, a fixed ratio drive mechanism in the form of a chain drive providing a torque delivery path between the intermediate shaft and the carrier of the gearset, a transfer clutch for connecting and releasing the first sheave of the variable drive mechanism and input shaft, a low brake, and a reverse brake.
• Mode bit added to computer hardware to indicate the currentmode: monitor (0) or user (1).• When an interrupt or fault occurs hardware switches to monitormodeuser monitorinterrupt/faultset user mode• Privileged instructions can be issued only in monitor mode.
Sharing system resources requires operating system to ensurethat an incorrect program cannot cause other programs toexecute incorrectly.• Provide hardware support to differentiate between at least twomodes of operations.1. User mode – execution done on behalf of a user.2. Monitor mode (also supervisor mode or system mode) –execution done on behalf of operating system.
I/O Protection
• All I/O instructions are privileged instructions.• Must ensure that a user program could never gain control ofthe computer in monitor mode (i.e., a user program that, aspart of its execution, stores a new address in the interruptvector).
Memory Protection
• Must provide memory protection at least for the interrupt vectorand the interrupt service routines.• In order to have memory protection, add two registers thatdetermine the range of legal addresses a program may access:– base register – holds the smallest legal physical memoryaddress.– limit register – contains the size of the range.• Memory outside the deļ¬ned range is protected.
CPU Protection
The CPU protection feature enhances the efficiency of an HP device’s CPU and Content Addressable Memory (CAM). Some denial of service attacks make use of spoofed IP addresses. If the device must create CAM entries for a large number of spoofed IP addresses over a short period of time, it requires excessive CAM utilization. Similarly, if an improperly configured host on the network sends out a large number of packets that are normally processed by the CPU (for example, DNS requests), it requires excessive CPU utilization. The CPU protection feature allows you to configure the HP device to automatically take actions when thresholds related to high CPU or CAM usage are exceeded.
How the CPU Protection Feature Works The CPU protection feature uses the concepts of normal mode and exhausted mode. The device transitions from normal mode to exhausted mode when specified thresholds for conditions related to high CPU usage and CAM usage are exceeded. When the device enters exhausted mode, actions can be taken to reduce the strain on system resources. You can define the conditions that cause the device to enter exhausted mode, the actions to take while the device is in exhausted mode, and the conditions that enable the device to go back to normal mode. For example, you can specify that a CPU usage percentage of 90% is a condition that will cause the device to go from normal mode to exhausted mode. When the device enters exhausted mode, you can specify that the action to take is to forward unknown unicast traffic in hardware instead of sending it to the CPU. You can further specify that a CPU usage percentage of 80% will cause the device to go back to normal mode.
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