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CRD_CONTROL is a system parameter that can be used to expand the function defined by CRDENABLE on Alpha and Integrity servers.

CRD_CONTROL is a bit mask for corrected read data (CRD) soft error control flags. These flags control the use of CRDERROR routines.

On Alpha and Integrity servers, the following bits are defined:

Bit Description
0 Enables CRD processing for all systems.
1 Enables scrubbing (rewriting) of the memory location that induced the CRD.
2 Enables page replacement of the pages that exhibit repeated CRD errors.
3 Forces all memory pages to be included in the PFN database. On systems that contain more than 512 megabytes of memory, all memory is mapped by the PFN database by default. This bit allows the mapping to occur on systems with less than 512 megabytes of memory.
4 Enables extended CRD handling, if available.
5 Enables loading of driver and process for handling server management events. Platform-specific code usually sets this bit if the required hardware and firmware support are available.
6 Disables CRD throttling.
7 Disables System Event Log (SEL) polling.
16-31 Reserved for platform-specific error-handling control.

On Alpha and Integrity servers, the default setting is 22, which enables scrubbing, page replacement, and extended CRD handling.