LPC Experiments

This configures the motherboard's LPC controller to forward ports necessary for sound cards to function on RUBY-9719VG2AR or a compatible motherboard using dISAppointment.

Currently implemented for Intel and AMD chipsets. However, be noted that the LDRQ# signal needed for LPC DMA has been removed since Intel 100 series (Skylake) and AMD Socket AM5/SP5 (Raphael/Genoa). While this program can still be used on those and newer systems as usual, DMA-related functions, namely digitized audio in DOS games, will not work. FM Synth, on the other hand, will still be able to work as it does not rely on DMA to function.

Currently only the Fintek F85226 LPC-ISA bridge is supported. It may be possible to support Winbond W83626, but the documentation on the configuration registers is a bit confusing, as it's currently uncertain how CRxx corresponds to the actual register address.

NOTE: AMD chipset support is based on existing documentations regarding the LPC bridge and is still WIP. So far no positive results with dISAppointment on AMD motherboards yet.

I. Preparation

Requires Open Watcom to build. I'm currently using Open Watcom 2.0.

You need to export the path where you installed Open Watcom into. For example:

export WATCOM=/opt/watcom

II. Building using Makefile

Currently the Makefile is meant for building the program on Linux.

Use make or make all to build all the programs.

For lpcen, lpccmd, lpcfchk, an additional build using the 0x2E/0x2F address pair instead of 0x4E/0x4F are provided, which will have a 2 after the initial filename.

Details on how to use each of the programs will be explained in Usage section.

III. Usage

DISCLAIMER: Be careful when using these programs as it may cause your system to malfunction if incorrect values were specified. All arguments in the programs are hexadecimal.

1. lpcen

This program enables the LPC-ISA bridge's configuration registers by writing 0x26 to the location 0x4E twice.

You need to run this once per system startup before you can use lpccmd.

2. lpccmd

lpccmd address [value]

This program reads/writes the value from/to the specified register address on the LPC-ISA bridge.

Enter only address to read, and enter both address and value to write. This program reads/writes 1 byte at a time.

You need to run lpcen or lpcfchk at least once before you can use it.

3. lpcfchk

This program checks the presence of Fintek F85226 LPC-ISA bridge, and displays some information about the states of some registers if the bridge is detected.

This program does not need lpcen to be run beforehand. It will enable the configuration registers on its own so you may also use lpccmd later on if needed.

4. pcicmd

pcicmd bus device function reg [value]

Similar to lpccmd, this program reads/writes the value from/to the register on the PCI device specified by bus, device and function number.

Enter bus, device, function and register to read. To write, additionally enter the value you need to write.

Keep note that this program reads/writes 4 bytes at a time so the register specified should be aligned to 4-byte boundary to ensure they are read/written correctly.

5. pcidump

pcidump bus device function > file

Similar to pcicmd, but this program reads all the registers from 0x00 to 0xFF of a given PCI device, 4 bytes at a time.

Use > file to output to file. If not specified, the program outputs all register values on screen (stdout).

6. amdpmcmd

amdpmcmd address [value]

This program reads/writes the value from/to the specified AMD PM register address (accessible via 0xCD6/0xCD7 pair).

Enter only address to read, and enter both address and value to write. This program reads/writes 1 byte at a time.

7. gencmd

gencmd size address [value]

This program reads/writes the value from/to the specified I/O port. You can specify any port up to 0xFFFF.

Enter the size and address to read, and additionally enter value to write. The size can be 1-4 bytes (3 is the same as 4).

8. lpcisa / lpcisav

This program configures the chipset's LPC controller for decoding specified address ranges. By default it configures the ranges useful for sound cards.

NOTE: This program no longer configures the LPC-ISA bridge, as it is optional to do so in most cases. You need to use other utilities such as lpcen, lpccmd and lpcfchk to inspect or make changes to the registers in the LPC-ISA bridge if needed.

lpcisa is the normal version. lpcisav contains some verbose information. Both programs are functionally identical.

lpcisa [base1 mask1] [base2 mask2] [base3 mask3] [base4 mask4]

Note that there may be too many lines of output to be displayed when running the program, especially with verbose output. You may want to consider redirecting the output to a file so you can examine it later, for example with lpcisav:

lpcisav > output.txt

The program will try to determine the system's chipset vendor by querying the root complex, and perform configurations accordingly.

For Intel chipsets, up to 4 sets of base addresses and masks can be configured.

For AMD chipsets, up to 3 sets of base addresses and masks can be configured.

Note that for AMD chipsets, masks behave differently. If set to 0, the range will be configured in alternative mode which limits to 16 bytes. Otherwise, it will be configured in normal mode which covers up to 512 bytes.

IV. References

Some useful reference documents can be found in the docs folder.

You may find additional documents for other chipsets on Intel and AMD's official sites.