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D.3
DIM Code Checkpoints
The Device Initialization Manager (DIM) gets control at various times during BIOS POST to initialize
different system busses. The following table describes the main checkpoints where the DIM module
is accessed:
Checkpoint
Description
2A
Initialize different buses and perform the following functions: Reset, Detect, and Disable
(function 0); Static Device Initialization (function 1); Boot Output Device Initialization
(function 2). Function 0 disables all device nodes, PCI devices, and PnP ISA cards. It also
assigns PCI bus numbers. Function 1 initializes all static devices that include manual
configured onboard peripherals, memory and I/O decode windows in PCI-PCI bridges, and
noncompliant PCI devices. Static resources are also reserved. Function 2 searches for and
initializes any PnP, PCI, or AGP video devices.
38
Initialize different buses and perform the following functions: Boot Input Device
Initialization (function 3); IPL Device Initialization (function 4); General Device
Initialization (function 5). Function 3 searches for and configures PCI input devices and
detects if system has standard keyboard controller. Function 4 searches for and configures
all PnP and PCI boot devices. Function 5 CONFIGURES all onboard peripherals that are set
to an automatic configuration and configures all remaining PnP and PCI devices.
DD-DE
OEM PCI init debug POST code during DIMM init. DEh during BUS number assignment and
DDh during ressource allocation, Hight byte is the BUS number.
While control is in the different functions, additional checkpoints are output to port 80h as a word
value to identify the routines under execution. The low byte value indicates the main POST Code
Checkpoint. The high byte is divided into two nibbles and contains two fields. The details of the
high byte of these checkpoints are as follows:
HIGH BYTE XY
The upper nibble 'X' indicates the function number that is being executed. 'X' can be from 0 to 7.
0 = func#0, disable all devices on the BUS concerned.
1 = func#1, static devices initialization on the BUS concerned.
2 = func#2, output device initialization on the BUS concerned.
3 = func#3, input device initialization on the BUS concerned.
4 = func#4, IPL device initialization on the BUS concerned.
5 = func#5, general device initialization on the BUS concerned.
6 = func#6, error reporting for the BUS concerned.
7 = func#7, add-on ROM initialization for all BUSes.
8 = func#8, BBS ROM initialization for all BUSes.
The lower nibble 'Y' indicates the BUS on which the different routines are being executed. 'Y' can
be from 0 to 5.
0 = Generic DIM (Device Initialization Manager).
1 = On-board System devices.
2 = ISA devices.
D-4
AT8001 User's Guide
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