Re: [PATCH v7 047/120] x86/cpu/amd: Refactor CPUID(0x1) level calculation

[Christian Ludloff]

On Thu, May 28, 2026 at 8:42 AM Ahmed S. Darwish <darwi@xxxxxxxxxxxxx> wrote:
>
> AMD K8 init code has the cryptic CPUID(0x1).EAX level check:
>
>     (level >= 0x0f48 && level < 0x0f50) || level >= 0x0f58
>
> Given that:
>
>     EAX[0:3] is the CPU stepping
>     EAX[4:7] is the CPU base model
>     EAX[8:11] is the base family ID, with 0xf as the largest
>     EAX[16:19] is the CPU extended model
>
> [...]

For K8 the 8-bit model field actually contained 3 distinct pieces
of information: bits 7...4 encoded process tech and K8 revision,
bits 3...2 encoded core type, core count, as well as cache size,
and bits 1...0 encoded socket type.

https://www.sandpile.org/x86/cpuid.htm#leaf_0000_0001h_Kn
right below the K7 section.

The rest of the AMD models were sane.

--
C.