Dell ICH8M + NVIDIA GPU Shutdown Fix for Inspiron 1520 and related models

[hidematu5310]

I have discovered a potential fix for the long-standing shutdown issues on the Dell Inspiron 1520 (ICH8M + NVIDIA GPU).

It appears that a significant delay (Sleep) is required to achieve a successful shutdown.

By writing 0 to SLP_SMI_EN to disable SMI generation, followed by a long Sleep command—specifically Sleep(0xFFFF) or at least Sleep(0x2710)—I have successfully achieved shutdowns on macOS 10.4 through 10.7, as well as 13, 14, and 15. Short delays like Sleep(0x10) or Sleep(0x16) invariably result in failure.

like:

Method (_PTS, 1, NotSerialized)
    {
        If (LEqual (Arg0, 0x05))
        {
            Store (Zero, SLPE)
            Sleep (0xFFFF)
        }
    }

The behavior varies across different macOS versions:
10.8 - 10.10: Unstable. Sometimes it succeeds, but often the screen goes black while the fans continue to spin, or the system reboots.
10.11 - 10.12: Always results in a reboot.
10.13 - macOS 12: The screen turns off, but the fans stay on indefinitely.

The reason why success rates are higher in very old and very new versions, while mid-era OS versions are unstable, remains unknown. Furthermore, it takes approximately 30 seconds to 1 minute for the hardware to complete the shutdown process. This suggests that the hardware requires a significantly longer time to prepare for power-off compared to other machines of the same generation. This is almost certainly due to a firmware bug.

While this is an unconventional fix, It is encouraging to find a working method for these models, which were previously thought to have no consistent solution for the shutdown problem.

may work for the following models:

• Inspiron 1420 / 1520 / 1720
• Vostro 1400 / 1500 / 1700
• XPS M1330

Note that rebooting is also unstable on these models, sometimes succeeding and sometimes failing, likely due to a similar underlying cause.

What I have tested so far:

 

• USB Power: Investigated behaviors around USB power, but it doesn't seem to be the cause.
• OSID: Tested with 0x10 (Windows XP) and 0x20 (Windows Vista), but with no significant change.
• BIOS Settings: Disabled LAN, Wi-Fi, Bluetooth, SDHC, and Module Bay in the BIOS, but the issue persists.

 

The following older thread might also be helpful for reference:

https://www.insanelymac.com/forum/topic/266803-dsdt-shutdown-nvidia-dells-not-zero-slpe-trick-alternate-ich8-method/

 

If you have any insights, suggestions, or ideas for a more fundamental solution, please let me know. Any feedback would be greatly appreciated!