System information

6.2 Host System Inspector
get repaired manually. But if the system of the node failed, the detection of the error source
is difficult. The CHARM card provides information which can identify the error source.
The following paragraphs list the status information which can be obtained by the CHARM
card while computer state detection is performed.
POST Code Provides information about hardware failures at boot time.
BIOS CMOS Content The CHARM card gets the BIOS CMOS content at boot time.
The CHARM VGA BIOS sends the CMOS content while running the init routine. The
CMOS content provides among others information about the system time, CMOS battery
status and the POST configuration status. Therefore, the CHARM can return the time
of the system start of the computer, the state of the CMOS configuration and provide
information whether the hardware of the system was changed since the last boot.
BIOS Interrupt Table The BIOS interrupt table contains the pointers to the interrupt
service routines. The interrupts are numbered and related to special tasks. For example,
the interrupt 0x10 is used to setup the active graphic card in the computer system. The
BIOS initializes the interrupt table at an early stage of the boot time. The CHARM
accesses the interrupt table with the aid of the PCI master interface. Therefore, it can
detect whether the CPU is workable at boot time. If the interrupt table is not initialized,
the BIOS is not executed - hence, the CPU is unworkable.
List PCI Devices The program lspci read out the configuration space of the PCI bus. The
CHARM card can detect all devices which are plugged into the same PCI bus segment like
itself with the aid of PCI Configuration cycles. Furthermore, the CHARM can recognized
whether the BIOS already initialized the PCI Configuration Space of the devices. If the
PCI BARs of a device are not initialized, the BIOS can crash before device initialization
or the device is disabled because of a malfunction. A Built-in Self Test (BIST) failure of a
device can cause the BIOS to deactivate it [40]. The BIST register is an optional capability
of PCI devices. It is part of the PCI Configuration space.
6.2.3 Analog Signal Measurement
Computer systems normally provide information about input voltage and temperature of
certain hardware units. Software tools read out these values and make them available to the
user. But if a system fails, there is no possibility to obtain this information. Some devices
like power supplies and expansion cards generally do not have a temperature sensor. The
CHARM integrates an ADC
3
to measure voltage and temperature values. The temperature
sensors are either directly connected to the CHARM card or connected to an expansion
board. A Linux kernel driver running on the ARM CPU provides access to the ADC.
The ADC has eleven ports which usage is summarized in table 6.1. As a sensor, negative
temperature coefficient thermistors (NTCs) are used to measure the temperature of certain
computer devices. The specific resistor of an NTC depends on the temperature. The
3
Analog-to-digital converter.
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