Mystery Cpuid Bit

And people say "never read the comments":

CL says: April 20, 2026 at 9:18 pm

I updated sandpile.org to reflect that

  Bit 19 = MP-capable
  Bit 18 = ECC-capable

Those were two distinct capabilities.

[sources: K7 µcode + K8 XOS-based public simulator published in 2000 + I worked at AMD back then]

That’s the NSA backdoor /s