topic Re: missing rdrand instruction on 3rd gen processors in Mobile and Desktop Processors

missing rdrand instruction on 3rd gen processors

RMitr1 — Mon, 25 Feb 2013 15:35:21 GMT

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):

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BV54. The RDRAND Instruction Will Not Execute as Expected

Problem:

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.

Implication:

Software will not be able to utilize the RDRAND instruction

Workaround:

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.

Status:

For the steppings affected, see the Summary Tables of Changes.

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If I read the spec update correctly, this could be fixed by a firmware update. What are the plans to issue this update?

Cheers,

Re: missing rdrand instruction on 3rd gen processors

idata — Tue, 26 Feb 2013 20:57:30 GMT

Thanks for the information.

Based on the Specification Update, a BIOS update may contain the fix for this situation. If required, we would recommend contacting the local support center for your region for additional information and verify if your product needs to be replaced.

Re: missing rdrand instruction on 3rd gen processors

RMitr1 — Mon, 04 Mar 2013 13:43:02 GMT

Since you have already marked your own response as 'correct answer', I understand there are in fact no known plans to fix this.