feat: emulator mode field, archive ZX81 standalone ROMs

emulator profiles support mode: standalone | libretro | both.
cross_reference.py skips standalone-only files for libretro platforms.
81.yml: type standalone + libretro, upstream ref added, files listed
with mode: standalone and source_refs to both codebases.
bios/Sinclair/ZX 81/: zx81.rom (8K) and dkchr.rom (4K) archived.

database.json

@@ -1,7 +1,7 @@
 {
-  "generated_at": "2026-03-18T15:11:54Z",
-  "total_files": 5565,
-  "total_size": 4908280385,
+  "generated_at": "2026-03-18T16:37:01Z",
+  "total_files": 5567,
+  "total_size": 4908292673,
   "files": {
     "520d3d1b5897800af47f92efd2444a26b7a7dead": {
       "path": "bios/3DO Company/3DO/3do_arcade_saot.bin",
@@ -47127,6 +47127,24 @@
       "sha256": "8a39aae2b2eb3c9fff09dc0d80bca9ffcb981f1665d9067ea1131129f3353b2b",
       "crc32": "37f87fac"
     },
+    "04e352ab6d6ca7f50109f67c850d9dc0f467de77": {
+      "path": "bios/Sinclair/ZX 81/dkchr.rom",
+      "name": "dkchr.rom",
+      "size": 4096,
+      "sha1": "04e352ab6d6ca7f50109f67c850d9dc0f467de77",
+      "md5": "5cba3a306fbb94454811ba262b27c958",
+      "sha256": "079ad784af12e6bf0b5c52a7b4d92da5ae4acddd0b13d73ec4221b49636a6c51",
+      "crc32": "761137d7"
+    },
+    "7b143ee964e9ada89d1f9e88f0bd48d919184cfc": {
+      "path": "bios/Sinclair/ZX 81/zx81.rom",
+      "name": "zx81.rom",
+      "size": 8192,
+      "sha1": "7b143ee964e9ada89d1f9e88f0bd48d919184cfc",
+      "md5": "db398d4e4e93a6d4dee3bfe146918219",
+      "sha256": "14ad84f4243efcd41587ff46ab932d11087043e8d455a1ed2a227b9657828dfa",
+      "crc32": "4b1dd6eb"
+    },
     "4f4b11ec22326280bdb96e3baf9db4b4cb1d02c5": {
       "path": "bios/Sinclair/ZX Spectrum/128-0.rom",
       "name": "128-0.rom",
@@ -55327,6 +55345,8 @@
       "cc78d4f4900f622bd6de1aed7f52592f": "77511fc58798404701f66b6bbc9cbde06596eba7",
       "0617321daa182c3f3d6f41fd02fb3275": "e33cdcdb69cd257b0b211ef46e7a8b144637db57",
       "27fbde30ffc81dbf909d4287be7c0f28": "cede52455ac2a92607b4a16b59a9296f9be3b78e",
+      "5cba3a306fbb94454811ba262b27c958": "04e352ab6d6ca7f50109f67c850d9dc0f467de77",
+      "db398d4e4e93a6d4dee3bfe146918219": "7b143ee964e9ada89d1f9e88f0bd48d919184cfc",
       "b4d2692115a9f2924df92a3cbfb358fb": "4f4b11ec22326280bdb96e3baf9db4b4cb1d02c5",
       "6e09e5d3c4aef166601669feaaadc01c": "80080644289ed93d71a1103992a154cc9802b2fa",
       "c1231a70b8129311216acb7479b031d5": "968937b1c750f0ef6205f01c6db4148da4cca4e3",
@@ -69789,6 +69809,12 @@
       "sram.dat": [
         "cede52455ac2a92607b4a16b59a9296f9be3b78e"
       ],
+      "dkchr.rom": [
+        "04e352ab6d6ca7f50109f67c850d9dc0f467de77"
+      ],
+      "zx81.rom": [
+        "7b143ee964e9ada89d1f9e88f0bd48d919184cfc"
+      ],
       "128-0.rom": [
         "4f4b11ec22326280bdb96e3baf9db4b4cb1d02c5"
       ],
@@ -77161,6 +77187,8 @@
       "6c7ef608": "77511fc58798404701f66b6bbc9cbde06596eba7",
       "00eeb408": "e33cdcdb69cd257b0b211ef46e7a8b144637db57",
       "37f87fac": "cede52455ac2a92607b4a16b59a9296f9be3b78e",
+      "761137d7": "04e352ab6d6ca7f50109f67c850d9dc0f467de77",
+      "4b1dd6eb": "7b143ee964e9ada89d1f9e88f0bd48d919184cfc",
       "e76799d2": "4f4b11ec22326280bdb96e3baf9db4b4cb1d02c5",
       "b96a36be": "80080644289ed93d71a1103992a154cc9802b2fa",
       "453d86b2": "968937b1c750f0ef6205f01c6db4148da4cca4e3",

emulators/81.yml

@@ -1,6 +1,7 @@
 emulator: EightyOne
-type: libretro
+type: standalone + libretro
 source: "https://github.com/libretro/81-libretro"
+upstream: "https://github.com/charlierobson/EightyOne"
 profiled_date: "2026-03-18"
 core_version: "1.0a"
 display_name: "Sinclair - ZX 81 (EightyOne)"
@@ -10,43 +11,34 @@ systems:
   - sinclair-zx81
 
 notes: |
-  EightyOne is a Sinclair ZX81 emulator ported to libretro. Also supports
-  ZX80, Jupiter ACE, TS1500, Lambda, R470, TK85, and ZX97LE machines, but
-  the libretro port hardcodes MACHINEZX81 in retro_load_game (libretro.cpp:393).
+  Libretro core embeds zx81.rom and dkchr.rom as C arrays (xxd -i at build).
+  Core never calls RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY.
+  Standalone EightyOne loads ROMs from filesystem (cwd/ROM/<filename>).
 
-  ROM loading is in snap.c:487-512. The memory_load() function matches the
-  requested ROM filename against a compiled-in table and copies from embedded
-  byte arrays generated by xxd -i at build time (Makefile.libretro:519-522).
-  Only two ROMs are embedded: zx81.rom (the ZX81 8K BASIC ROM) and dkchr.rom
-  (dK'tronics character ROM). Any other ROM name logs an error and returns 0.
+  Original emulator supports ~15 machines (ZX80, ZX81, Jupiter ACE, TS1500,
+  Lambda, R470, TK85, ZX97LE, Spectrum variants). Libretro port hardcodes
+  MACHINEZX81 — only zx81.rom and dkchr.rom are embedded.
 
-  The core never calls RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY, never opens
-  files from the filesystem for ROM data, and need_fullpath is set to false
-  (libretro.cpp:308). All ROM data is baked into the compiled .so/.dll.
+files:
+  # mode: standalone = only needed when running as standalone emulator
+  # mode: libretro = only needed when running as libretro core
+  # mode: both (default if absent) = needed in both modes
 
-  No external BIOS or firmware files are needed.
+  # ref: 81-libretro/81/zx81/snap.c:37,489-496 — embedded as bin_ROM_zx81_rom
+  # ref: EightyOne/Source/zx81/snap.cpp:1219-1279 — open(cwd/ROM/zx81.rom)
+  - name: zx81.rom
+    system: sinclair-zx81
+    required: true
+    mode: standalone
+    size: 8192
+    note: "ZX81 8K BASIC ROM. Embedded in libretro core, external for standalone."
+    source_ref: "EightyOne/Source/zx81/snap.cpp:1264, 81-libretro/81/zx81/snap.c:489"
 
-files: []
-
-analysis:
-  embedded_roms:
-    zx81_rom:
-      variable: bin_ROM_zx81_rom
-      source_file: "bin/ROM/zx81.rom"
-      build_step: "xxd -i -> C array"
-      source_ref: "snap.c:489-498"
-    dkchr_rom:
-      variable: bin_ROM_dkchr_rom
-      source_file: "bin/ROM/dkchr.rom"
-      build_step: "xxd -i -> C array"
-      source_ref: "snap.c:499-508"
-  machine_roms:
-    notes: |
-      eo.c sets CurRom based on machine type. The libretro port forces
-      MACHINEZX81 (eo.c:39-41), so CurRom is always zx81.ROM81 which
-      defaults to "zx81.rom". Other machine ROMs (zx80, ace, ts1500,
-      lambda, zx97le, ringo470, tk85) are referenced but only zx81.rom
-      and dkchr.rom are embedded. Selecting other machines would log
-      "ROM not found" and load nothing.
-  filesystem_access: false
-  system_directory_used: false
+  # ref: 81-libretro/81/zx81/snap.c:38,499-508 — embedded as bin_ROM_dkchr_rom
+  - name: dkchr.rom
+    system: sinclair-zx81
+    required: false
+    mode: standalone
+    size: 4096
+    note: "dK'tronics character ROM. Embedded in libretro core."
+    source_ref: "81-libretro/81/zx81/snap.c:499"

scripts/cross_reference.py

@@ -106,6 +106,13 @@ def cross_reference(
             if not fname:
                 continue
 
+            # Skip standalone-only files when comparing against libretro
+            # platforms (RetroArch, Lakka, etc.). These files are embedded
+            # in the core and don't need to be in the platform pack.
+            file_mode = f.get("mode", "both")
+            if file_mode == "standalone":
+                continue
+
             in_platform = fname in platform_names
             in_repo = _find_in_repo(fname, by_name, by_name_lower)