PC Processors

[aj_]

Requesting cpuid function ID 0x80000006 on a Ryzen 7 3700X returns 0x01009140.

So the value for the L3 cache associativity (bits 12-15) is 0x9

According to the spec(PDF page 75) this value is reserved.

Any idea were the issue lies here?

Is the spec wrong or the CPU bugged?

Edit: We now have a Ryzen 5 3600 which shows also returns 0x9 bits 12-15.

[avk · Accepted solution]

No, that L2/L3 cache associativity value (0x9) means "Please look at CPUID.8000_001D"

[aj_]

Thank you for the clarification.

Where in the docs is that noted?

I can't find it in

https://www.amd.com/system/files/TechDocs/54945_3.03_ppr_ZP_B2_pub.zip

Is that the wrong doc?

Am 22.10.19 um 22:12 schrieb avk:

Community <https://community.amd.com/?et=watches.email.thread>

>

Re: Ryzen 7 3700X: cpuid function ID 0x80000006 returns wrong

number for L3 cache associativity

in /Processors/

[avk]

The ZP-B2 document is about Zen 1+, not Zen 2 . Please read this: https://www.amd.com/system/files/TechDocs/56176_ppr_Family_17h_Model_71h_B0_pub_Rev_3.06.zip, page 74. BTW, the best way to check AMD Tech Doc updates is to visit here: https://www.amd.com/en/support/tech-docs 

Also, AMD still didn't explain at least 6 (six!) CPUID flags of their CPUs. Do you wish to know which ones?

[aj_]

Perfect.

I looked here:

https://developer.amd.com/resources/developer-guides-manuals/ and

couldn't find anything newer than my linked document.

Also, AMD still didn't explain at least 6 (six!) CPUID flags of their

CPUs. Do you wish to know which ones?

Sure, why not?

[avk]

Here they are:

8000_0007.EBX[04] - appeared along with Zen 2;

8000_0008.EBX[10, 13, 19, 23] - appeared along with Zen 2.

8000_000A.EDX[11] - appeared along with Piledriver;

8000_001F.EAX[16] - appeared along with Zen 2.

See it for yourself in my tiny utility avkSI, at the "Flag2" & "Flag3" tabs.

BTW, Intel also has an unexplained (publically) CPUID bit, 0000_0007[0].EDX[13]. I think it somehow is connected with those Spectre/Meltdown/etc. patches. I've noticed that bit in Skylake (i5-6300HQ) + Win10 v1903, along with 0000_0007[0].EDX[10] = MD-Clear.