docs: stop presenting Threadripper 68+68=137 W as a correct RAPL sum

docs/explanation/rapl.md

@@ -78,6 +78,13 @@ counting!)
 
 **Correct approach**: Use only psys (9.6W) ✅
 
+A second, unrelated double-count shows up on some multi-die AMD CPUs
+(Threadripper / EPYC): `package-0-die-0` and `package-0-die-1` can both
+expose the **same** socket-wide energy counter. They are not two
+independent packages. Summing identical readings multiplies CPU power
+by the die count. See the Threadripper teaser below and
+[issue #1274](https://github.com/mlco2/codecarbon/issues/1274).
+
 ## CodeCarbon's RAPL Strategy
 
 CodeCarbon implements intelligent domain selection to provide reliable
@@ -124,7 +131,9 @@ and consistent measurements:
 -   `core` reports very low energy values
 -   Unclear if `core` is included in `package` (vendor documentation is
     sparse)
--   Multiple dies may report as separate packages (e.g., Threadripper)
+-   Multiple dies may report as separate packages (e.g., Threadripper).
+    On some parts those domains mirror the same socket-wide counter;
+    summing identical readings double-counts CPU power.
 
 **What RAPL Does NOT Measure**:
 
@@ -164,8 +173,26 @@ We investigate RAPL on various architectures :
 Desktop computer with AMD Ryzen Threadripper 1950X 16-Core (32 threads)
 Power plug measure when idle (10% CPU): 125 W
 package-0-die-0: 68 W | package-0-die-1: 68 W | CodeCarbon: 137 W
+
+⚠️  WRONG: 68 W + 68 W = 137 W. The two dies report the same
+    socket-wide RAPL counter (issue 1274). This is one meter read
+    twice, not two independent 68 W packages. CPU RAPL here is
+    ~68 W, not 137 W.
 ```
 
+!!! warning "Mirrored per-die RAPL counters"
+
+    Two dies reporting the exact same 68 W is not a coincidence. On
+    some multi-die AMD CPUs the Linux powercap `package-*-die-*`
+    domains all read one socket-wide energy counter. CodeCarbon's
+    Linux RAPL path still sums them today, so this 137 W figure is
+    the known over-count, not a confirmed-correct reading. The
+    Windows EMI backend already drops mirrored channels. A later
+    kernel on the same machine can expose a single `package-0`
+    instead (see the detailed Threadripper section below). Tracking:
+    [#1274](https://github.com/mlco2/codecarbon/issues/1274),
+    [#1276](https://github.com/mlco2/codecarbon/pull/1276).
+
 ### Laptop: Intel(R) Core(TM) Ultra 7 265H (TDP 28W)
 
 **Idle Measurements**:
@@ -301,19 +328,24 @@ Total Power Consumption: 181.05 Watts
 280 - 100 (idle) = 180 W
 
 Analysis:
-- Each die independently measured via RAPL
+- This capture exposes a single package-0 domain (kernel-dependent)
+- It is not the mirrored 68 W + 68 W case in the teaser above
 - No psys domain available on this AMD system
 - RAPL counter range: 234 sec at 280W (potential wraparound consideration)
 ```
 
 **AMD RAPL Characteristics**:
 
--   Multi-die CPUs report separate packages (package-0-die-0,
-    package-0-die-1)
+-   Multi-die CPUs may report separate packages (package-0-die-0,
+    package-0-die-1). On some parts those domains **mirror the same
+    socket-wide counter**; summing identical readings double-counts
+    CPU power (the 68 W + 68 W → 137 W teaser above). Distinct
+    counters (for example two sockets) should still be added.
 -   No psys domain available on older AMD processors
 -   `core` domain reports very low values (unclear if included in
     package)
--   Package measurements are generally reliable for total CPU power
+-   A single, non-mirrored package reading is generally reliable for
+    total CPU power
 
 ## Key Takeaways for RAPL Measurements
 
@@ -346,7 +378,9 @@ Analysis:
 7.  **Platform-specific behavior**:
     -   Intel modern: package or psys (with prefer_psys=True)
     -   Intel older: package-0 for CPU only
-    -   AMD: Sum all package-X-die-Y for multi-die CPUs
+    -   AMD: use package domains. If several `package-X-die-Y`
+        domains report the same energy, keep one — do not sum
+        mirrors. Sum only domains with distinct counters.
 8.  **Limitations**: RAPL does NOT measure:
     -   Discrete GPUs (use nvidia-smi/rocm-smi)
     -   SSDs, peripherals, fans