Why does the BIOS entry point start with a WBINVD instruction?

Question

I\'m investigating the BIOS code in my machine (x86_64 Linux, IvyBridge). I use the following procedure to dump the BIOS code:

$ sudo cat /proc/iomem | grep ROM
         


        

Answer 1

According to this Dr. Dobb's article written by Pete Dice of Intel back in 2011:

Because the processor cache is not enabled by default, it is not uncommon to flush cache in this step with a WBINV instruction. The WBINV is not needed on newer processors, but it doesn't hurt anything.

I'm not sure what WBINVD has to do with cache not being enabled by default. I thought he might have meant that WBINVD would enable the cache but the documentation doesn't say anything about the instruction having this effect. I think the second sentence confirms Margaret's suspicion that this is a case of cargo cult.