diff --git a/bios/Other/syobonaction/coin.ogg b/bios/Other/syobonaction/coin.ogg
new file mode 100644
index 00000000..b654123e
Binary files /dev/null and b/bios/Other/syobonaction/coin.ogg differ
diff --git a/bios/Other/syobonaction/powerup.ogg b/bios/Other/syobonaction/powerup.ogg
new file mode 100644
index 00000000..723fdfe7
Binary files /dev/null and b/bios/Other/syobonaction/powerup.ogg differ
diff --git a/emulators/dosbox-staging.yml b/emulators/dosbox-staging.yml
index 163ddb69..760d91ae 100644
--- a/emulators/dosbox-staging.yml
+++ b/emulators/dosbox-staging.yml
@@ -588,20 +588,16 @@ files:
 
   - name: "default.sf2"
     path: "soundfonts/default.sf2"
-    description: "General MIDI SoundFont"
+    description: "SoundFont named by the default soundfont setting"
     required: false
-    aliases:
-      - "GeneralUser-GS.sf2"
-      - "FluidR3_GM.sf2"
-      - "Fluid_R3_GM_GS.sf2"
-      - "4gmgsmt-sf2_04-compat.sf2"
-      - "4GMGSMT.SF2"
-      - "synthgs-sf2_04-compat.sf2"
+    unsourceable: "name the operating system gives the SoundFont it installs as default, not shipped with the program; a same-named file of another program must not stand in"
     note: >
-      any SoundFont loads; GeneralUser GS, Fluid R3, the AWE32 4MB GM/GS/MT
+      default value of the soundfont setting: the name picks the default
+      SoundFont when the operating system installs one, usually Fluid R3.
+      Any SoundFont loads; GeneralUser GS, Fluid R3, the AWE32 4MB GM/GS/MT
       bank and the Trevor0402 SC-55 SoundFont are recognised by filename or
       RIFF INFO name and get their own reverb, chorus and filter presets
-    source_ref: "src/midi/fluidsynth.cpp:672-689, src/midi/fluidsynth.cpp:816-883, src/midi/fluidsynth.cpp:1229-1242"
+    source_ref: "src/midi/fluidsynth.cpp:672-689, src/midi/fluidsynth.cpp:816-883, src/midi/fluidsynth.cpp:1227-1242"
 
   # -- PCjr system ROM --
 
diff --git a/emulators/dosbox-x.yml b/emulators/dosbox-x.yml
index 09aada1c..cd22c6e6 100644
--- a/emulators/dosbox-x.yml
+++ b/emulators/dosbox-x.yml
@@ -270,6 +270,7 @@ files:
     aliases:
       - "FluidR3_GM.sf2"
       - "GeneralUser_GS.sf2"
+    unsourceable: "probed at fixed operating system paths, where the system's own SoundFont sits; a same-named file of another program must not stand in"
     note: >
       any SF2 or SF3 file loads; fluid.soundfont names it and
       fluid_synth_sfload is the only check
diff --git a/emulators/nekop2.yml b/emulators/nekop2.yml
index 15f1db0b..a390872c 100644
--- a/emulators/nekop2.yml
+++ b/emulators/nekop2.yml
@@ -29,17 +29,20 @@ systems: [pc-98]
 
 files:
   # -- Main BIOS ROM --
-  # Loaded in bios/bios.c:232-235 via getbiospath(). 96 KB (0x18000)
+  # Loaded in bios/bios.c:232-237 via getbiospath(). 96 KB (0x18000)
   # mapped at 0xe8000. Without this, the built-in BIOS simulator
-  # (nosyscode + BIOS_SIMULATE) is used.
+  # (nosyscode + BIOS_SIMULATE) is used (bios/bios.c:253).
   - name: "bios.rom"
     path: "np2/bios.rom"
+    min_size: 98304
+    validation: [size]
     required: false
     hle_fallback: true
     note: >
-      PC-9801 system BIOS ROM (96 KB). The core boots without it using
-      the built-in BIOS simulator, but some software requires the real BIOS.
-    source_ref: "bios/bios.c:232-235, common/strres.c:53"
+      PC-9801 system BIOS ROM. The first 0x18000 bytes are read to 0xe8000;
+      a file shorter than that is ignored and the built-in BIOS simulator
+      is used, as when the file is absent.
+    source_ref: "bios/bios.c:232-237, common/strres.c:53"
 
   # -- PC-9821 extension BIOS --
   # Loaded in bios/bios.c:262-266 via getbiospath(). 8 KB (0x2000)
diff --git a/emulators/np2kai.yml b/emulators/np2kai.yml
index bb457ceb..f9c72765 100644
--- a/emulators/np2kai.yml
+++ b/emulators/np2kai.yml
@@ -35,18 +35,21 @@ systems: [pc-98]
 
 files:
   # -- Main BIOS ROM --
-  # Loaded in bios/bios.c:430-436 via getbiospath(). 96 KB (0x18000) mapped
-  # at 0xe8000. Only loaded when np2cfg.usebios is true (core option).
-  # Without this, CopyMemory copies nosyscode[] built-in simulator.
+  # Loaded in bios/bios.c:440-447 via getbiospath(). 96 KB (0x18000) mapped
+  # at 0xe8000. Only loaded when np2cfg.usebios is set, which is the default
+  # (pccore.c:129) and has no core option. Without this, CopyMemory copies
+  # the nosyscode[] built-in simulator (bios/bios.c:463).
   - name: "bios.rom"
     path: "np2kai/bios.rom"
-    size: 98304
+    min_size: 98304
+    validation: [size]
     required: false
     hle_fallback: true
     note: >
-      PC-9801 system BIOS ROM (96 KB). The core boots without it using the
-      built-in BIOS simulator, but some software requires the real BIOS.
-    source_ref: "bios/bios.c:450-456, common/strres.c:60"
+      PC-9801 system BIOS ROM. The first 0x18000 bytes are read to 0xe8000;
+      a file shorter than that is ignored and the built-in BIOS simulator
+      is used, as when the file is absent.
+    source_ref: "bios/bios.c:440-447, pccore.c:129, common/strres.c:67"
 
   # -- Font file --
   # Path set in libretro.c:1813 as "<system>/np2kai/font.bmp".