AMD Geode/Video 3/Script

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This is a work in progress textual description of the video.

Accessibility notice[edit | edit source]

Narrator: "Quick notice: A full textual description of this video is linked in the description below. Enjoy!"

A glossy purple slide shows the text "A full textual description of this video is linked in the description below"

Recount[edit | edit source]

Narrator: "Welcome back to my AMD Geode repair video series. If you weren't here for the first few videos, let me give you a quick recount."

A glossy red slide shows the text "Welcome back! Now for a quick recap"

Narrator: "In video 1 I bought and did some basic troubleshooting on an AMD Geode computer board. I drew some wrong conclusions and at the end damaged the board with bad soldering."

Two scenes from part one are shown. The first is me using a bench power supply to power board. The second is a sticky mess of me soldering the board. The text "Part 1: Troubleshooting" is shown.

Narrator: "In video 2 I spent 6 hours trying to repair the board. I was successful in the end but damaged another part later."

Two scenes from part two are shown. The first is soldering an inductor back on to the board. The second is running solder braid over the network adapter with bent and ruined network pins. The text "Part 2: Repair" is shown.

Lessons learned[edit | edit source]

Narrator: "Okay we're done. Let's talk about the lessons learned."

A glossy green slide shows the text "Lessons learned"

Narrator: "First, make a plan when soldering. Practice on e-waste to see if it's something you can do. Take breaks throughout and assess the situation. I didn't do any of these and I damaged the board."

A glossy green slide shows the the following text:

  • Lesson 1: Have a plan
  • Practice it on e-waste
  • Take breaks
  • Assess the situation
  • I didn't do these and failed

Narrator: "Secondly, understand the circuit properly! Had I done this I wouldn't have even had to solder the board. Let me explain."

A glossy orange slide shows the the following text:

  • Lesson 2:
  • Understand the circuit!
  • I could've avoided soldering altogether

Narrator: "In the video I drew this diagram"

A picture of the circuit board near the CPU is shown. Text and lines are drawn over it, forming a diagram that shows:

  • DAVdd connects to the LM4041AIM3-1.2 voltage reference
  • From the 1.22 volt reference a 0.25 nanofarad capacitor and 10 kiloohm resistor in parallel run to DVREF
  • The 1.21 kiloohm resistor follows from the DVREF capacitor and resistor to the DRSET pin

Narrator: "I also measured these voltages"

The diagram is updated. DAVdd is marked as 3.3 volts, DVREF is 1.22 volts and DRSET is 40 millivolts.

Narrator: "How is DAVdd 3.3 volts if it's connected to a 1.2 volt reference?"

The voltage reference is circled.

Narrator: "How is DVREF 1.22 volts if there's a 10k resistor?"

The 10k resistor is circled instead.

Narrator: "What is this capacitor doing here?"

The capacitor is circled instead.

Narrator: "It makes no sense!"

Three giant question marks are shown overlaid the diagram.

Narrator: "When it comes to the part of the board I spend time troubleshooting and soldering, it gets worse!"

A picture of the circuit board near is shown, near the VGA output port. It contains various surface mount chips, but in the center is a set of 3 small capacitors, 7 inductors, 3 ESD diodes and 7 resistors.

Narrator: "I thought this circuit had the video signals travelling through capacitors, through inductors, through these ESD diodes, and out through these termination resistors."

Text overlays the diagrams labels the capacitors, inductors, ESD diodes and resistors. The top three capacitors are labelled R, G and B. Three separate lines from each of these capacitors draw through a set of inductors, ESD diodes and resistors. The lines are coloured red, green and blue.

Narrator: "I figured that an ESD diode was faulty, pulling a signal line down to GND. This would be responsible for the low voltage."

The text "Would a bad ESD diode pull the signal low?" is shown. The green line is replaced with a shorter line that ends at one of the pins of its ESD diode.

Narrator: "Had I just measured the ESD resistors with my multimeter in resistance and diode mode I could've ruled this out."

A cartoon multimeter is shown with its black probe on the GND pin of the ESD diode and the red probe on the signal pin of the ESD diode.

Narrator: "Even then, I decided to remove the capacitors to isolate the signals"

The circuit board is shown again, this time with the top capacitors removed. The red, green and blue lines stop at the signal side of the capacitor and no longer flow to the inductors. The text "I removed the capacitors to rule out any fault..."

Narrator: "But these are connected to GND, not the signal!"

The red, green and blue lines turn to crossed out stubs. The text "But they weren't connected to the signal!" is shown.

Narrator: "Removing them would not show the fault at all! I was doomed from the start."

The red, green and blue lines start again at the inductors and flow to the resistors again.

Writing code[edit | edit source]

Narrator: "Without an obvious board issue, maybe I could find some hints in the chip itself?"

A glossy blue slide shows the text "Investigating the chip"

Narrator: "So I opened the data sheet and started looking for anything useful."

The datasheet cover page is shown. An 'AMD Geode' logo is shown as well as the text "AMD Geode™ LX Processors Data Book" dated February 2009.

Narrator: "I first looked at the at the video processor diagnostic register."

A table titled "MSR_DIAG_VP Bit Descriptions" is shown. It has these fields:

  • RSVD: Reserved
  • CM: 32-Bit CRC Mode. Selects 32-bit CRC generation
  • NDM: New Dither Mode. Selects either the legacy dither mode, or new dither mode
  • SM: Sim Mode. This field is used to put the VP in modes to aid verification
  • DVAL: DAC Test Value. 8-bit data value to drive to CRT DAC when selected by bit 19
  • D: DAC Test Value Select. Selects which data stream is sent to CRT DAC during CRT DAC test mode
  • RSVD: Reserved. Reserved for test purposes. Set to 000 for normal operation
  • SP: Spares. Read/write, no function

Narrator: "I found some interesting fields that can be used to test the video processor DAC."

Three fields are shown in more detail. I will quote from the data sheet here:

Bits 27 to 20: DAC Test Value

8-bit data value to drive to CRT DAC when selected by bit 19.

Duplicate copies of DAC Test Value are driven on DAC RGB.

  • crt_dac_r[7:0] = DAC Test Value[7:0] ([27:20] is this register)
  • crt_dac_g[7:0] = DAC Test Value[7:0] ([27:20] is this register)
  • crt_dac_b[7:0] = DAC Test Value[7:0] ([27:20] is this register)

To enable DAC Test Value to be driven to CRT DAC:

  • (DAC Test Value Select must = 0) AND
  • ((VTM[6] = 0 AND MBD_MSR_DIAG[18:16] = 101h) OR
  • (VTM[6] = 1 AND VTM[3:0] = 0001h)

Bit 19: DAC Test Value Select

Selects which data stream is sent to CRT DAC during CRT DAC test mode.

  • 0: 24-bit data to CRT DAC = {3{DAC Test Value[27:20]}} (3 time repeated 8-bit value).
  • 1: 24-bit data to CRT DAC = gfx_data[23:0] (raw input from Display Controller).

Bits 18:16: RSVD

Reserved. Reserved for test purposes. Set to 000 for normal operation.

Narrator: "It looks complicated, but it's quite straight forward. Here's how to use it:"

The text "How to use DAC test mode:" is shown on screen.

Narrator: "Don't. Save yourself. This is a nightmare of problems."

The single word "Don't" is shown in the center of the screen.

Narrator: "First: The MBD_MSR_DIAG register doesn't exist."

The three fields are shown again, with the "MBD_MSR_DIAG" register circled.

Narrator: "I googled it, it only has three results"

Top of a google results page is shown. It says there are about 3 results.

Google helpfully says "It looks like there aren't many great matches for your search"

The text "Google knows 3 results:" is shown on screen.

Narrator: "The top one is my website!"

Three Google results are shown:

The text "The top result is my website!" is shown on screen.

Narrator: "It's probably a typo for GLD_MSR_DIAG."

The GLD Diagnostic MSR register is shown, named GLD_MSR_DIAG.

It has a note: "This register is reversed for internal use by AMD and should not be written to."

The text "Maybe it meant GLD_MSR_DIAG?" is shown on screen.

Narrator: "But that makes no sense! It's reserved for AMD!"

The note about it being reserved is circled.

The text "But it's reserved and not for use?"

Narrator: "Maybe it's a typo for the reserved field I saw earlier?"

The three diagnostic fields from earlier are shown. The RSVD field is circled.

The text "Perhaps it meant the RSVD field?" is shown on screen.

Narrator: "The bit fields line up, both reference bits 18 to 16."

The numbers "18:16" are circled twice, with an arrow pointed between them.

The first instance is in the text "MBD_MSR_DIAG[18:16]".

The second instance is the bits for the RSVD field.

The text "The bit fields both match" is shown on screen.

Narrator: "I went to set the registers and found it's a mix of MSRs and memory mapping."

The VP Diagnostic MSR (MSG_DIAG_VP) and Video Processor Test Mode (VTM) registers are shown.

MSG_DIAG_VP has an MSD address of 48002010h.

VTM has a VP Memory Offset of 130h.

The text "They use a mix of MSRs and memory mapping?" is shown on screen.

Narrator: "The documentation on how to use these is fairly confusing."

Excerpts from the GeodeLink datasheet section are shown, including Table 4-2. MSR Mapping and the Memory and I/O Mapping section. Both have a lot of complicated wording and require further context to understand.

Narrator: "I gave up and just edited the Linux driver to set registers for me."

The following source code is shown:

/* Enable test mode? */
#define VP_DIAG_MSR 0x48002011
u64 diag_val = 0;
u64 vtm_val = 0;
diag_val |= (128 << 27); /* DVAL = 128 */
/* diag_val D is already 0 */
diag_val |= (0x5 << 18); /* RSVD = 0b101 */
/* VTM[6] is already 0 */
wrmsrl(VP_DIAG_MSR, diag_val);
write_vp(par, VP_VTM, dcfg);

The text "I just edited the Linux driver:" is shown on screen.

Narrator: "...and it just made the screen go black."

The text "Test mode just made the screen go black" is shown on screen.

Narrator: "So what else is there to check?"

The text "What next?" appears on the screen"

Narrator: "I found a register that lets you use an external DAC VREF"

The DCFG register is shown. The following field is highlighted:

Select DAC VREF. Allows use of an external voltage reference for CRT DAC.

  • 0: Disable external VREF.
  • 1: Use external VREF.

The text "Maybe using another DAC VREF would help?" is shown on the screen.

Narrator: "Changing it didn't help."

The text "Unfortunately not" appears on the screen.

Narrator: "I did find some DAC power registers."

The MISC register is partially shown. The following fields are shown:

Bits 63 to 13: RSVD (RO)

Reserved (Read Only). Reads back as 0.

Bit 12: SP

Spare. Read/write; no function.

Bit 11: APWRDN

Analog Interface Power Down. Enables power down of the analog section of the internal CRT DAC.

  • 0: Normal.
  • 1: Power down.


DAC Power Down. Enables power down of the digital section of the internal CRT DAC.

For this bit to take effect:

VP Memory Offset 130h[6] must be = 1 or

MSR Address 48000010h[18:16] must not equal 101.

  • 0: Normal.
  • 1: Power down.

The text "Maybe the DAC is powered down?" is shown on screen.

Narrator: "But I confirmed these were set properly."

The text "Nope, these are set fine" appears on the screen.

Narrator: "I found the GLCP_DAC register"

The GLCP_DAC register is partially shown. The following fields are shown:

Bits 64 to 14: RSVD


Bit 13: SB (RO)

Status Blue (Read only). A logic level 1 means the Blue DAC output is above 0.35V.

Bit 12: SG (RO)

Status Green (Read only). A logic level 1 means the Green DAC output is above 0.35V.

Bit 11: SR (RO)

Status Red (Read only). A logic level 1 means the Red DAC output is above 0.35V.


Internal Reference Enable. Internal reference enable to the DAC.

Bit 9: OL

Output Level.

  • 0: RGB
  • 1: TV - for testing only, analog TV out is not supported).

Bits 8 to 6: AB

Adjust for Blue DAC.

  • 000: 0%.
  • 011: 7.5%
  • 100: -10%.
  • 111: -2.5%.

The text "I found the GLCP_DAC register" is shown on screen.

Narrator: "It has fields showing the output voltage"

The status registers are circled.

The text "It reports on the DAC output" is shown on screen.

Narrator: "It correctly reports the output as being low voltage"

The text "Correctly reports low voltage" appears on screen.

Narrator: "Well, that wasn't too helpful."

The text "That was unhelpful" is the only thing shown on the screen.

Measurement[edit | edit source]

Narrator: "Let's go back and measure the DAC VREF. Again."

A glossy red slide shows the text "Let's measure the DAC VREF again!"

Narrator: "Here's a microscope shot of the circuit."

A microscope photo from above showing the same DAC VREF circuit from before.

Narrator: "Here's the components labelled again."

Three components are labelled:

  • A 12nF capacitor
  • A 1.21k resistor
  • A 10k resistor
  • The 1.2v voltage reference

Narrator: "and here are the signal lines labelled correctly:"

Five lines are drawn over PCB tracks. These connect:

  • The 1.21k resistor between DRSET and GND
  • The 12nF cap between DVREF and GND
  • The 1.2v VREF between DVREF and GND
  • The 10k resistor between DVREF and 3.3v

Narrator: "For now let's focus on the DVREF line."

Only the DVREF track is shown, and only the 1.2 volts VREF is labelled.

The text "Let's focus on DVREF" is shown on screen.

Narrator: "DVREF measures 1.2 volts correctly, but"

A cartoon multimeter is shown, with its black probe on a GND rail and red probe on the DVREF rail.

The text "DVREF measures 1.2V" is shown on screen.

Narrator: "Linux booting drops it to 0.8 volts!"

The Linux mascot is shown in the corner on screen. The mascot is NewTux, created by Larry Ewing using The GIMP and turned in to a slick vector by gg3po.

The text "Linux drops it to 0.8V!" in shown on screen.

Narrator: "All along I should've measured when the fault was active!"

The text "Lesson learned: Measure DURING the fault" is shown on screen.

Narrator: "Measuring the 3.3 volt rail shows it's 0.9 volts"

The 3.3v rail is shown on screen.

The multimeter measures between GND and the 3.3v rail.

The text "3.3V rail is 0.8V?" is shown on screen.

Narrator: "As a quick check I bridged the 3.3 volt rail to a nearby working rail"

A microscope shot of shaky tweezers approaching two components is shown.

The first is a capacitor component elsewhere on the board, the other is the 10k resistor in the DAC VREF section.

The tweezers touch both components and provide a path for the DAC VREF to get 3.3v.

One capacitor is the to connect the 3.3v rail to a nearby capacitor on a separate 3.3v rail is shown.

The text "Bridging to a nearby 3.3V rail" is shown.

Narrator: "Surprisingly this fixed the brightness"

A monitor is shown with cut-off text on it:

come to Alpine Linux 3.15

nel 5.16.0-rc2+ on an i586 (dev/tty1)

alhost login:

The camera briefly zooms out and shows an orange frog squeeze doll on its back. There's a hole on its underside that makes it look like a gaping butt hole.

I didn't need to text describe that but I did. I also can't fix it because I filmed it over a year ago.

Narrator: "I checked the other side of the board and found this:"

Microscope footage of a circuit board is shown.

A yellowed resistor and capacitor are shown next to each other.

The text "The other side of the board:" is shown on screen.

Narrator: "A blown resistor!"

The view zooms in on the resistor, showing a small hole in the middle.

The resistor is marked 01Y, meaning 1 ohm!

The text "Blown 1Ω resistor!" is shown on screen.

Narrator: "And a yellowed capacitor!"

The view zooms in on the capacitor.

The text "Yellow capacitor!" is shown on screen.

Repair[edit | edit source]

Narrator: "Time to finally repair something"

A glossy yellow slide shows the text "Repair time!"

Narrator: "I used my soldering iron to remove the nearby capacitor and the resistor."

The microscope shows the same scene as before.

Tweezers hold the yellowed capacitor while a large square soldering iron touches its side.

Narrator: "I heated up one side of each component and forced that end away from its pad"

The solder on the capacitor melts on one side and the tweezers pull the component to stand up.

The iron then melts one side of the resistor while holding it with the tweezers.

The resistor slips and bends sideways, disconnecting from the opposite pad.

A part of capacitor remains on the pad.

Narrator: "Then heated the other side up and pulled the component away"

The iron melts the resistor's pad again and the tweezers pull it away.

Part of the resistor remains on this pad too.

The same happens with the capacitor, leaving part of its remains too.

Narrator: "Next I ran a wire to replace the resistor"

The soldering heats up both resistor pads and cool to hold a small wire in place to bridge them.

Narrator: "Then cleaned up the soldering mess"

A cotton tip is used to remove all the soldering flux from the board.

The board is shown post-clean.

Narrator: "Do not do this!"

The text "Do not do this!" appears.

Narrator: "First, did I need to remove both components?"

The board is shown again, with the resistor and capacitor circled.

The text "Should I have removed both?" is shown.

Narrator: "Finding a suspicious voltage drop could have identified the bad component".

A multimeter is shown probing either side of the blown resistor.

The text "Measuring voltage drop would show the problem component" is shown.

Narrator: "Secondly, I removed the components wrong"

An orange cartoon resistor sits on a an abstract blue circuit board.

The text "I removed components wrong" is shown.

Narrator: "I forced heat through one end of the component"

A cartoon soldering iron touches the end of the resistor. A gradient of red heat from a soldering iron heats up one end of the component, with the other end still cool.

The text "I heated up the component" is shown.

Narrator: "This let me lift one end up"

The cooled component is shown partially lifted up, with one end floating above the previously heated pad, and the other end attached to the other pad.

The text "Then lifted only one end up" is shown.

Narrator: "But I risked pulling up the other end's pad"

The resistor is now transparent, revealing the other pad has actually been partially lifted from the board. The pad is circled.

The text "But risked lifting the other pad" is shown.

Narrator: "The proper way to desolder this is using a hot air gun"

The resistor is back attached to the board and a large circular gradient of heat from above is shown heating up the resistor and board.

The text "Hot air would desolder both pads" is shown.

Narrator: "Then removing the component using tweezers"

The resistor is now completely gone from the board, with the board and pads still hot.

The text "Then tweezers for removal" is shown.

BIOS editing[edit | edit source]

this still didn't fix the issue

linux works, maybe the BIOS is broken?

i checked the BIOS using modbin6 to see if it enabled CRT out by default

couldn't use awdflash DOS bios flasher over serial even if wanted

no way to flash chips as a backup PM49FL004TJ chips for backup

Ethernet removal[edit | edit source]

- pins missing, confusion about IRDYB

- hot air 40 mins

- testing on stuff

- melted the clock connector

BIOS flashing[edit | edit source]

- months later? (check wiki)

- ram didn't detect well

- debian 12

- flashrom, hot swapping

- different bioses had no change

- ram broke again

- good ram made it work?

Conclusion[edit | edit source]


- credits