Thinkpad X1 Tablet 3rd Gen (i5-8250U): Black screen

[Baio77]

I bought this fantastic Tablet, I've been going crazy for a few days to have the video working on the integrated display (3000x2000). I leave everything in my possession attached and I hope someone can decipher the logs and understand the problem. I can only view the video on external screen via TB3 Dock.

https://drive.google.com/drive/folders/1JjNKLTJrNsqpnTw9fECbo_dMTV4x1JUH?usp=share_link

[Jake Lo]

You'll need to change DVMT. Not sure if the system has the option in the BIOS

[Hervé]

Graphics settings to use for KBL R UHD620 iGPU are:

1. KBL framebuffer layout 0x591B0000 or 0x59160000
2. iGPU device id 0x5916 (or 0x5912 apparently)

Layouts 0x87C000-- normally are for Amber Lake systems.

SMBIOS should be MBP15,2 with MBP15,4 probably fine as well.

Of course, DVMT will need to be set at 64MB minimum in BIOS for 4K output, it won't be achievable with DVMT set to 32MB. There are no workaround to this.

[Baio77]

Thanks for the replies and I have a few questions: Patch stolenmem solves the DVMT problem in theory, this determines whether the PC boots or not. So I think the problem is elsewhere as logic. Much more likely a connector issue, I think. I would like to extrapolate as much information as possible and try to understand the problem and actually determine NOT compatibility with Hackintosh. For a complete debug I add kext debug in the traditional efi and related botargs??? Here I extrapolate info on video connectors???? Thanks for the valuable info.

[Hervé]

No, the stolenmem patch (alongside the fbmem patch) solves the OS X/macOS graphics framebuffer memory problem encountered since Yosemite with Broadwell (& later) iGPUs. It does not address in any way the 64MB+ DVMT requirement for 4K, nor the black screen issue. See this thread, in our FAQ section, for information on the matter of DVMT and framebuffer memory patches.

 

As for your tablet's screen, do try and identify the fitted connector type. There are Windows and Linux tools for that. Look it up.

[Baio77]

https://ibb.co/CKrKrGP

 

I went back to this problem , fixed it and now the graphics work . Just for acknowledgment, you can bypass the Bios problem with IGPU patches.
I'm editing the post tonight and attaching everything, I'm interested in your opinion.

 

Quote

                <key>PciRoot(0x0)/Pci(0x2,0x0)</key>
                <dict>
                    <key>AAPL,GfxYTile</key>
                    <data>AQAAAA==</data>
                    <key>AAPL,ig-platform-id</key>
                    <data>AAAbWQ==</data>
                    <key>AAPL,slot-name</key>
                    <string>Internal</string>
                    <key>device-id</key>
                    <data>G1kAAA==</data>
                    <key>device_type</key>
                    <string>VGA compatible controller</string>
                    <key>force-online</key>
                    <data>AQAAAA==</data>
                    <key>framebuffer-con1-busid</key>
                    <data>BQAAAA==</data>
                    <key>framebuffer-con1-enable</key>
                    <data>AQAAAA==</data>
                    <key>framebuffer-con1-index</key>
                    <data>AQAAAA==</data>
                    <key>framebuffer-con2-busid</key>
                    <data>BAAAAA==</data>
                    <key>framebuffer-con2-enable</key>
                    <data>AQAAAA==</data>
                    <key>framebuffer-con2-index</key>
                    <data>AgAAAA==</data>
                    <key>framebuffer-con2-type</key>
                    <data>AAQAAA==</data>
                    <key>framebuffer-fbmem</key>
                    <data>AACQAA==</data>
                    <key>framebuffer-patch-enable</key>
                    <data>AQAAAA==</data>
                    <key>framebuffer-stolenmem</key>
                    <data>AACgAQ==</data>
                    <key>framebuffer-unifiedmem</key>
                    <data>/////w==</data>
                    <key>model</key>
                    <string>Intel Graphics UHD 620</string>
                </dict>

EDIT:

I found the patch on the net by a miracle