9600M GT works on external display but no internal LVDS on Olivetti AIO (possible MSI

[Mick1819]

Hi everyone,
I'm working on an old Olivetti all-in-one system that appears to be based on an MSI OEM motherboard (labeled G35T-TG, Intel G35 chipset), although I'm not 100% sure about the exact board model. I can provide photos if needed.
The system originally came with an NVIDIA GeForce 8400 GS (MXM, 256MB DDR2), which works perfectly with the internal display.

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Goal
Upgrade the GPU to a GeForce 9600M GT (MXM-II, DDR2, 64KB VBIOS, MS-V149B).

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Current situation

• The 9600M GT powers on and works
  
• System boots normally
  
• Windows loads
  
• External display (DVI) works perfectly
  

BUT:

• No image on internal display (LVDS)
  
• No BIOS/logo → completely black screen
  

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What I tested
1. BIOS settings

• Tried PEG / IGD / Auto options
  
• No change
  

2. Hardware checks

• GPU properly seated
  
• Cooling and power OK
  
• External output confirms GPU is working
  

3. VBIOS analysis

• Dumped VBIOS from both GPUs
  
• Compared 8400 GS vs 9600M GT using hex tools
  
• The VBIOS files are significantly different, not just minor variations
  
• Differences are spread across many regions, not isolated blocks
  

4. VBIOS mod attempt

• Tried copying suspected LVDS/init sections
  
• Result: GPU failed to initialize (black screen everywhere, required recovery)
  

5. Cross comparison

• Compared my 8400 GS VBIOS with Acer versions
  
• They are also very different, not matching dumps
  
• Suggests OEM-specific variations or different board implementations
  

6. Recovery & tools

• I already prepared a proper flashing setup
  
• Used NVFlash and tested recovery procedures
  
• I have full backups of all original VBIOS files
  
• Comfortable with reflashing and recovery
  

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Additional note
When working on the VBIOS, I’m not sure if I may have been looking at the wrong sections.
I was not able to clearly identify LVDS-related tables or display initialization blocks, and the structure of the VBIOS makes it difficult to isolate the relevant parts.

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Possible causes (not sure)

• Differences between G86 (8400 GS) and G96 (9600M GT) display initialization
  
• LVDS panel configuration or timing mismatch
  
• OEM-specific VBIOS or motherboard limitations
  
• Different LVDS wiring or output routing
  

I'm not sure which of these is the actual cause, so any insight would help.

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Question
Has anyone:

• Successfully used a 9600M GT MXM in an AIO system like this?
  
• Found a compatible VBIOS that enables LVDS output on similar hardware?
  
• Seen similar incompatibilities when moving from G86 to G96?
  

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Summary

• 8400 GS → internal display works
  
• 9600M GT → external only
  
• System boots fine
  
• Issue = LVDS initialization / firmware incompatibility
  

I can provide motherboard and GPU photos if needed.
Thanks in advance 🙏