Specifications

AMD Geode™ GeodeROM Functional Specification 13
Overview
32087C
INT 15h Functions
Function 24h (A20 Gate Support)
Contains functions for enabling, disabling, and querying the status of the A20 Gate.
Function 87h (Extended Memory Block Move)
Provides traditional 286 PC/AT-style service to applications, drivers, and operating systems that move blocks of
memory to, from, or within extended RAM while executing in real mode.
Function 88h (Get Extended Memory Size)
Provides traditional PC/AT-style service as a means of reporting the amount of installed, extended system DRAM
(up to 64 MB) to the operating system.
Function 89h (Enter Protected Mode)
Switches the system into protected mode with support for 286 and higher technology.
Function BEh (ACCESS.bus and NVRAM Access Method)
GeodeROM contains AMD-specific BIOS calls for accessing devices on an ACCESS.bus. A caller provides an
ACCESS.bus address and can read or write the device.
GeodeROM contains AMD-specific BIOS calls for accessing data in NVRAM. The caller is not required to know
details about the location of this data, but may use the predefined tokens to read or write data in NVRAM.
Function C0h (Get ROM Configuration)
Returns a pointer to the ROM configuration tables that contains system information such as model, sub-model,
and other features.
Function C1h (Get EBDA)
Returns the segment address of the EBDA.
Function C2h (PS/2 Mouse Support)
There is optional support for a standard PS/2 mouse in GeodeROM. This is comprised of code to initialize the
mouse, the INT 15h Function C2h calls, and the INT 74h code to handle IRQ 12.
Function E8h (Memory Size and Memory Map)
GeodeROM contains support for the E8h functions for determining the system memory size (Function E801h) and
for building a system memory map (Function E820h).
INT 16h (IRQ1 Keyboard Services)
Provides INT 16h keyboard services via a small IBM-style option ROM. GeodeROM also includes an IRQ1 handler to
process incoming scan codes and manage the circular scan code buffer that resides in the BDA (BIOS Data Area). To
support applications and drivers that intercept scan codes, the IRQ1 handler forwards all scan codes to the INT 15h,
Function 4Fh scan code redirect. The keyboard code also supports calling INT 1Bh for Ctrl-Break functionality.
INT 17h (Parallel Port BIOS Support)
Supports the standard INT 17h interface for initializing, getting status, and writing data to the parallel port.
INT 1Ah (PCI BIOS INT Support)
Provides a real mode, INT 1Ah interface to many of the B1h class subfunctions defined in revisions 2.2 and newer of
the PCI BIOS Specification.
INT 1Ah (System Time/Date Functions)
Supports most of the standard functions for setting and viewing the system time and date, as well as setting the
alarm.
Companion Device Register Initialization
Downloads a table of default values into the PCI-ISA bridge portion of the Geode device following a power-on reset.
Subsequent code sequences (e.g., VSA2 software) may change the default values as features are enabled, disabled,
or reconfigured.
LCD Panel Initialization
GeodeROM can configure and enable an LCD flat panel. TFT panels are supported by default. The system designer
selects the panel type and resolution in order to include this support.