Compal POST diagnostic card

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This article is linked to by Flashing_a_BIOS_chip_with_Bus_Pirate and Flashing_KB9012_with_Bus_Pirate

Contents

Introduction

In the cases of BIOS failure or a minor hardware malfunction, POST codes could be really helpful to find out why your computer is not booting, at what booting stage it is stuck. You could write down these codes and look them up online or ask knowledgeable people.

Example: incomplete list of coreboot POST codes . Other codes could be found by running

cd ./coreboot/
find . -type f -print0 | xargs -0 grep "post_code"


Many desktop motherboards have a POST display for these codes, but probably there are no laptops with it. If you have a laptop and would like to see its' POST codes, you need to buy a special POST card like this:

[*] Compal POST diagnostic card - example 1 (~$15.18)

[*] Compal POST diagnostic card - example 2 (~$16.44)

This card could be inserted to MiniPCI-E port of laptop's motherboard instead of WiFi adapter, or connected to a special header with included wires. According to my research, this card is compatible with at least 68% laptop motherboards' MiniPCI-E port:

Laptop MB company Approximate market share Compatible?
Compal 35% V
Quanta 33% V
Wistron 13%  ?
Inventec 7%  ?
Pegatron 6%  ?
Foxconn 3%  ?
ECS 2%  ?
Other 1%  ?
Total compatible 68% V

Even for those laptop motherboards which are not exposing the POST codes through MiniPCI-E port - most of them have some kind of debug port (sometimes without a soldered header) - to which it is also possible to connect this POST card, just harder...

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Compatibility

To understand if this card is compatible with your laptop motherboard's MiniPCI-E port, find out a motherboard's manufacturer - this is not equal to laptop's manufacturer! (which in fact just assembles a laptop and puts their logo on it) . Usually you could find this information, as well as motherboard's model number, written on a motherboard (need to disassemble a laptop to look), or maybe try to look it up online. If this manufacturer is not Compal/Quanta, you could try looking through a datasheet for this board (if it is available publicly) to see if it is exposing the POST codes, and - if yes - through what interface

NOTE: the example links above are for 2013 revision of POST card. You could see its' supported interfaces at this table: (MiniPCI interface can't be seen at new laptop designs so it was omitted)

Revision / Interface MiniPCI MiniPCI-E LPC Serial port (Compal only)
2009 V V V -
2011 V V V -
2013 - V V V

USAGE ADVICE: insulate the back of this POST card, to protect it from short circuit by touching motherboard / motherboard's radiator / MiniPCI-E cylindrical screw stand ; also, preserve the correct polarity while connecting to avoid the damage to a card

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Structure

Compal POST card structure.png

1) MiniPCI-E: support for LPC interface at Compal and other supported motherboards

2) LPC interface: second way to connect to laptop's motherboard

3) Serial port: alternative way to connect to laptop's motherboard

4) Dedicated chips: for processing the MiniPCI-E, LPC and serial port signals

5) Two seven-segment displays: for displaying the diagnostic results

6) Factory interface: used only by POST card's manufacturer (to flash its' firmware?)

7) LEDs: display the status of CLK and RST signals

CLK is blinking during the normal operation of POST card - if it was connected to the compatible laptop motherboard which has been turned on later (don't insert/extract the POST card while the motherboard is powered)

RST lights when the card gets LPC Reset (LRSTJ) signal.

If the POST card is stuck at EE code or cycles between 00 and EE, it could be that a card is faulty... If it is stuck at 00 code, it is probably because the motherboard is incompatible or its' BIOS is empty (has not been flashed or flashed improperly)

More information about this card could be obtained at Compal_POST_diagnostic_card_-_Additional

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Connectivity

This POST card could be connected to MiniPCI-E port, as well as LPC and serial port. Here is a pinout of its' MiniPCI-E interface:

Pin # Name Pin # Name
51 EC_RX_P80_CLK 52 +3.3V
49 EC_TX_P80_DATA 50 GND
47 48
... ...
21 22
19 LCLK 20
17 LRSTJ 18 GND
15 GND 16 LAD0
13 14 LAD1
11 12 LAD2
9 GND 10 LAD3
7 8 LFRAME
5 6
3 4 GND
1 2


This POST card receives the serial debug information from laptop's motherboard through EC RX/TX signals:

G505s la-a091p EC RX TX connections.png

These signals could be listened to by connecting to the card's 4-pin debug port...