Acer Altos G520 series, Service Manual

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Chapter 4 74
Checkpoint
Diagnostic LED Decoder
Description G=Green, R=Red, A=Amber
MSB LSB
37 OFF G A A
Displaying sign-on message, CPU information, setup key message,
and any OEM specific information.
38 G OFF R R
Initializes different devices through DIM. See DIM Code Checkpoints
section of document for more information.
39 G OFF R A Initializes DMAC-1 and DMAC-2.
3A G OFF A R Initialize RTC date/time.
3B G OFF R A
Test for total memory installed in the system. Also, Check for DEL or
ESC keys to limit memory test. Display total memory in the system.
3C G G R R Mid POST initialization of chipset registers.
40 OFF R OFF OFF
Detect different devices (Parallel ports, serial ports, and coprocessor
in CPU, … etc.) successfully installed in the system and update the
BDA, EBDA…etc.
50 OFF R OFF R
Programming the memory hole or any kind of implementation that
needs an adjustment in system RAM size if needed.
52 OFF R G R
Updates CMOS memory size from memory found in memory test.
Allocates memory for Extended BIOS Data Area from base memory.
60 OFF R R OFF Initializes NUM-LOCK status and programs the KBD typematic rate.
75 OFF A R A Initialize Int-13 and prepare for IPL detection.
78 G R R R Initializes IPL devices controlled by BIOS and option ROMs.
7A G R A R Initializes remaining option ROMs.
7C G A R R Generate and write contents of ESCD in NVRam.
84 R G OFF OFF Log errors encountered during POST.
85 R G OFF G Display errors to the user and gets the user response for error.
87 R G G G Execute BIOS setup if needed / requested.
8C A G OFF OFF Late POST initialization of chipset registers.
8D A G OFF G Build ACPI tables (if ACPI is supported)
8E A G G OFF Program the peripheral parameters. Enable/Disable NMI as selected
90 R OFF OFF R Late POST initialization of system management interrupt.
A0 R OFF R OFF Check boot password if installed.
A1 R OFF R G Clean-up work needed before booting to operating system.
A2 R OFF A OFF
Takes care of runtime image preparation for different BIOS modules.
Fill the free area in F000h segment with 0FFh. Initializes the Microsoft
IRQ Routing Table. Prepares the runtime language module. Disables
the system configuration display if needed.
A4 R G R OFF Initialize runtime language module.
A7 R G A G
Displays the system configuration screen if enabled. Initialize the
CPU’s before boot, which includes the programming of the MTRR’s.
A8 A OFF R OFF Prepare CPU for operating system boot including final MTRR values.
A9 A OFF R G Wait for user input at config display if needed.
AA A OFF A OFF
Uninstall POST INT1Ch vector and INT09h vector. Deinitializes the
ADM module.
AB A OFF A G Prepare BBS for Int 19 boot.
AC A G R OFF End of POST initialization of chipset registers.
B1 R OFF R A Save system context for ACPI.
00 OFF OFF OFF OFF Passes control to OS Loader (typically INT19h).