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I happen to have one of those processors from stepping E1/L1/N0 that do not execute the rdrand instruction, because it was 'forgotten' in a cpuid register.
From the Specupdate (jan 2013):
BV54. The RDRAND Instruction Will Not Execute as Expected
On processors that support the RDRAND instruction, that capability should be reported via the setting of CPUID.01H:ECX.RDRAND[bit 30]. Due to this erratum, that bit will not be set, and the execution of the RDRAND instruction will result in a #UD exception.
Software will not be able to utilize the RDRAND instruction
It is possible for the BIOS to contain a workaround for this erratum to report RDRAND as present via CPUID and allow proper execution of RDRAND.
For the steppings affected, see the Summary Tables of Changes.
If I read the spec update correctly, this could be fixed by a firmware update. What are the plans to issue this update?