Lenovo Y540-15IRH internal graphics problem

[Roman555]

Hi there! I need some help or piece of advice.

A friend of mine kindly asked me to look into his notebook because I have some necessary experience. It's NM-C221 rev 2. A schematics and a boardview I've already downloaded here. Thanks!

Preface: The notebook was in a professional workshop years ago where some job was done, some bios image was flashed and original backup image was lost. So all this time the notebook has been working using discrete graphics with unknown bios image (but someway compatible, because it was updated by a Lenovo utility).

Problem: The notebook won't run if graphics cards settings of BIOS has been switched to internal graphics, settings has been saved and the notebook has restarted. It has been just black screen. This problem the workshop couldn't solve. They just re-flashed bios chip and asked to not switch. A discrete graphics is default option in BIOS.

I've supposed the problem is the bios with not-cleaned ME so I've downloaded a right dump (with cleaned ME) and flashed it. A mainboard with RAM and heatsink has been plugged to power supply (no CMOS or power battery) and to external monitor via HDMI. In the BIOS settings a graphics option has been switched to on-board graphics by myself. I haven't seen any picture on the monitor after it.
To revive the mainboard the BIOS chip (GD25B127D) has been flashed again. GD25B127D is OK and I've seen its ID in BIOS image (Intel Flash Image Tool (FIT) has 'said' about it).

Question: Can wrong BIOS prevent normal work of internal graphics? If it's not what is then? Is it possible at all using on-board graphics to see image on an external monitor via HDMI ? As I've seen in the schematics: HDMI (and also DP USB-C) signals connected right into nvidia chip. On the board there is a eDP-switching chip that switches signal from graphic cards to LCD panel.

Thank everyone for answers!

[mcplslg123]

Re: Lenovo Y540-15IRH internal graphics problem

This mb will work with discrete only and i dont see any opion in schematic which indicates that its switchable. However, flashing a known good clean me bios should restore the settings to default,i.e discrete.

[Roman555]

Re: Lenovo Y540-15IRH internal graphics problem

This mb will work with discrete only and i dont see any opion in schematic which indicates that its switchable. However, flashing a known good clean me bios should restore the settings to default,i.e discrete.

I would say the schematics shows the only eDP is switchable. I also know for sure that the option is used to be workable on LCD panel until that mentioned incident.
I just remember a desktop technology Lucid Virtu when a customer could use both videocards via one video port. Maybe there is something like that in this model of a laptop, isn't it ?

[mcplslg123]

Re: Lenovo Y540-15IRH internal graphics problem

Honestly.i'm not sure as my expertise dont lies in this aspect.

[Roman555]

Re: Lenovo Y540-15IRH internal graphics problem

Recently I tried to switch the graphics again. This time the LCD panel was connected. And it was the same - black screen, no booting. No luck. When I disassembled the laptop I saw a strange spot on a CPU die and a corresponding spot on a heat-sink without thermal grease. I remember for sure that the last time thermal grease was covered evenly all the CPU die. I suppose a local overheating could cause such defect.
The resistance of VCCGFXCORE to GND is about 0.5 Ohm. Is it too low? I guess internal graphics is fail. So I flashed a SPI chip again. There will be no more experiments of switching graphics in this notebook.