HP Vectra VL800, Technical Reference Manual

Page: 65 / 147

65
3 System Board
The Input/Output Controller Hub 2 (82801BA)
HP Hardware Monitoring
The hardware monitoring chip is on the system board. Its responsibility
includes status panel management (LEDs), early diagnostics (CPU,
memory, PLLs, boot start), run-time diagnostics (CPU errors), fan speed
regulation, and other miscellaneous functions.
The integrated microprocessor includes a Synopsys cell based on Dallas
“8052” equivalent, a 2 KB boot ROM, 256 bytes of data RAM, an I
2
C cell, an
Analog-to-Digital (ADC) with 5 entries, and an additional glue logic for
interrupt control, fan regulation, and a status panel control.
The hardware monitoring chip downloads its code in 96 milliseconds from
an I
2
C serial EEPROM. The total firmware (8051-code, running in RAM) size
is 14 KB. As it exceeds the 2 KB program RAM space, a paging mechanism
will swap code as it is required, based on a 512 byte buffer. The first 2 KB
pages of firmware code is critical because it controls the initial power
on/reset to boot the system. This initial page is checked with a null-
checksum test and the presence of hardware monitoring markers (located
just below the 2 KB limit).
Hardware monitoring information is not accessible in I/O space or memory
space of the system platform, but only through the SMBUS (which is a sub-
set of the I
2
C bus), via the ICH2. Its I
2
C cell may operate either in Slave or
Master mode, switched by firmware, or automatically in the event of
‘Arbitration’ loss.
Hardware monitoring reports critical errors at start-up, and is therefore
powered by Vstandby (3.3V) power. For it to work, the PC must be
connected to a grounded outlet. This enables the PC’s hardware monitoring
chip to be active, even if the system has been powered off.