diff --git a/doc/9-guides/emulation-cores.md b/doc/9-guides/emulation-cores.md
index e067976dd..2624f6ddc 100644
--- a/doc/9-guides/emulation-cores.md
+++ b/doc/9-guides/emulation-cores.md
@@ -37,13 +37,13 @@ Furnace achieves the authentic sound of videogame hardware by emulating sound ch
 
 - **OPL/OPL2/Y8950 core**:
   - **Nuked-OPL3**: high quality OPL emulation core. slightly off due to tiny differences between OPL and OPL3, but otherwise it is good.
-  - **ymfm**: lower (?) CPU usage.
+  - **ymfm**: this core is supposed to use less CPU than Nuked-OPL3, but for some reason it actually doesn't.
   - **YM3812-LLE**: a new core written by the author of the Nuked cores. it features extremely accurate emulation.
     - this core uses a *lot* of CPU time. may not be suitable for playback!
 
 - **OPL3 core**:
   - **Nuked-OPL3**: high quality OPL emulation core.
-  - **ymfm**: lower (?) CPU usage.
+  - **ymfm**: this core is supposed to use less CPU than Nuked-OPL3, but for some reason it actually doesn't.
   - **YMF262-LLE**: a new core written by the author of the Nuked cores. it features extremely accurate emulation.
     - this core uses even more CPU than YM3812-LLE. not suitable for playback or even rendering if you're impatient!