Resolve Windows 11 24H2 BSOD Issues with WD SN770 and SN580 Registry Hack

Microsoft’s latest operating system update, Windows 11 version 24H2, has introduced a series of undocumented bugs, particularly affecting disk performance. Users have reported frustration over being unable to remove 8.63 GB of data post-upgrade. Additionally, the Windows SFC scan function appears to be malfunctioning; however, Microsoft has acknowledged this issue and is addressing it with the forthcoming KB5044384 update.

Moreover, several users are facing complications specifically with Western Digital NVMe SSDs, as these drives are experiencing blue screen crashes after the Windows 11 24H2 upgrade.

The issues are notably occurring with the WD_Black SN770 and WD Blue SN580 models, both of which lack dedicated DRAM chips and instead utilize system memory for caching through host memory buffer (HMB). Affected users have determined that the root of the problem lies in improper allocation of the host memory buffer size, and adjustments made through the Registry Editor appear to resolve the issue.

For those unaware, many SSDs incorporate a dedicated DRAM component that serves as a buffer to manage metadata between the NAND flash memory and the controller. This DRAM cache enhances write performance and minimizes random access delays. In contrast, NVMe SSDs that do not feature DRAM typically utilize HMB technology, enabling the controller to utilize system memory via Direct Memory Access (DMA).

Normally, NVMe SSDs allocate around 64 MB of memory on Windows; however, they can extend this allocation to 100 MB or more. This discrepancy is pivotal as users affected by the issue have observed their HMB allocation climbing up to 200 MB on the SN770 and SN580 models, which likely triggers conflicts leading to the blue screen errors (BSOD).

Unfortunately, determining the HMB allocation size directly on Windows can be challenging without third-party utilities, such as VLO’s hmb-nvme application.

Fortunately, there is a simple workaround using the Registry Editor to adjust the problem. By modifying the DWORD value within the “HmbAllocationPolicy”key located in the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\StorPort directory, users can set the allocation back to 64 MB. The steps to accomplish this are as follows:

1. Launch the Registry Editor by executing REGEDIT.
2. Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\StorPort directory.
3. If not already present, create a new HmbAllocationPolicy subkey.
4. Adjust the DWORD value for the key to either 0 or 2 (where 0 = HMB allocation off, and 2 = HMB allocation set to 64 MB).
5. Restart your computer.

If these steps restore functionality, it is likely that the HMB allocation was the underlying cause. Users with SSDs from other brands facing similar problems are encouraged to apply this Registry adjustment until an official Windows update or firmware upgrade resolves the situation permanently.

Source: WD forum

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