diff --git a/src/mame/subsino/subsino.cpp b/src/mame/subsino/subsino.cpp
index c064e7f3bcb..14c9f9c4075 100644
--- a/src/mame/subsino/subsino.cpp
+++ b/src/mame/subsino/subsino.cpp
@@ -223,7 +223,7 @@ To Do:
 ***************************************************************************/
 
 #include "emu.h"
-#include "subsino_m.h"
+#include "subsino_crypt.h"
 
 #include "cpu/z180/hd647180x.h"
 #include "machine/i8255.h"
@@ -3901,7 +3901,8 @@ ROM_END
 
 void subsino_state::init_victor5()
 {
-	subsino_decrypt(machine(), victor5_bitswaps, victor5_xors, 0xc000);
+	uint8_t *rom = memregion( "maincpu" )->base();
+	subsino_decrypt(rom, victor5_bitswaps, victor5_xors, 0xc000);
 
 	m_flash_packet = 0;
 	m_flash_packet_start = 0;
@@ -3914,12 +3915,14 @@ void subsino_state::init_victor5()
 
 void subsino_state::init_victor21()
 {
-	subsino_decrypt(machine(), victor21_bitswaps, victor21_xors, 0xc000);
+	uint8_t *rom = memregion( "maincpu" )->base();
+	subsino_decrypt(rom, victor21_bitswaps, victor21_xors, 0xc000);
 }
 
 void subsino_state::init_crsbingo()
 {
-	subsino_decrypt(machine(), crsbingo_bitswaps, crsbingo_xors, 0xc000);
+	uint8_t *rom = memregion( "maincpu" )->base();
+	subsino_decrypt(rom, crsbingo_bitswaps, crsbingo_xors, 0xc000);
 
 	m_flash_packet = 0;
 	m_flash_packet_start = 0;
@@ -3932,12 +3935,14 @@ void subsino_state::init_crsbingo()
 
 void subsino_state::init_sharkpy()
 {
-	subsino_decrypt(machine(), sharkpy_bitswaps, sharkpy_xors, 0xa000);
+	uint8_t *rom = memregion( "maincpu" )->base();
+	subsino_decrypt(rom, sharkpy_bitswaps, sharkpy_xors, 0xa000);
 }
 
 void subsino_state::init_sharkpye()
 {
-	subsino_decrypt(machine(), victor5_bitswaps, victor5_xors, 0xa000);
+	uint8_t *rom = memregion( "maincpu" )->base();
+	subsino_decrypt(rom, victor5_bitswaps, victor5_xors, 0xa000);
 }
 
 void subsino_state::init_smoto20()
@@ -3955,8 +3960,7 @@ void subsino_state::init_smoto13()
 void subsino_state::init_tisub()
 {
 	uint8_t *rom = memregion( "maincpu" )->base();
-
-	init_victor5();
+	subsino_decrypt(rom, victor5_bitswaps, victor5_xors, 0xc000);
 
 	/* this trips a z180 MMU core bug? It unmaps a region then the program code jumps to that region... */
 	rom[0x64c8] = 0x00;
@@ -3970,8 +3974,7 @@ void subsino_state::init_tisub()
 void subsino_state::init_tisuba()
 {
 	uint8_t *rom = memregion( "maincpu" )->base();
-
-	init_victor5();
+	subsino_decrypt(rom, victor5_bitswaps, victor5_xors, 0xc000);
 
 	/* this trips a z180 MMU core bug? It unmaps a region then the program code jumps to that region... */
 	rom[0x6491] = 0x00;
@@ -3984,9 +3987,8 @@ void subsino_state::init_tisuba()
 
 void subsino_state::init_tisubb()
 {
-	subsino_decrypt(machine(), tisubb_bitswaps, tisubb_xors, 0xc000);
-
 	uint8_t *rom = memregion( "maincpu" )->base();
+	subsino_decrypt(rom, tisubb_bitswaps, tisubb_xors, 0xc000);
 
 	/* this trips a z180 MMU core bug? It unmaps a region then the program code jumps to that region... */
 	rom[0x60da] = 0x00;
diff --git a/src/mame/subsino/subsino2.cpp b/src/mame/subsino/subsino2.cpp
index 806845f92ad..b67c6a763bb 100644
--- a/src/mame/subsino/subsino2.cpp
+++ b/src/mame/subsino/subsino2.cpp
@@ -55,8 +55,8 @@ by the otherwise seemingly unnecessary internal ROMs.
 ************************************************************************************************************/
 
 #include "emu.h"
+#include "subsino_crypt.h"
 #include "subsino_io.h"
-#include "subsino_m.h"
 
 #include "cpu/h8/h83048.h"
 #include "cpu/i86/i186.h"
@@ -3583,7 +3583,7 @@ ROM_END
 
 void subsino2_state::init_mtrain()
 {
-	subsino_decrypt(machine(), crsbingo_bitswaps, crsbingo_xors, 0x8000);
+	subsino_decrypt(memregion("maincpu")->base(), crsbingo_bitswaps, crsbingo_xors, 0x8000);
 }
 
 
@@ -3618,7 +3618,7 @@ ROM_END
 
 void subsino2_state::init_tbonusal()
 {
-	subsino_decrypt(machine(), sharkpy_bitswaps, sharkpy_xors, 0x8000);
+	subsino_decrypt(memregion("maincpu")->base(), sharkpy_bitswaps, sharkpy_xors, 0x8000);
 }
 
 /***************************************************************************
@@ -3919,7 +3919,7 @@ ROM_END
 
 void subsino2_state::init_wtrnymph()
 {
-	subsino_decrypt(machine(), victor5_bitswaps, victor5_xors, 0x8000);
+	subsino_decrypt(memregion("maincpu")->base(), victor5_bitswaps, victor5_xors, 0x8000);
 }
 
 GAME( 1996, mtrain,   0,        mtrain,   mtrain,   subsino2_state, init_mtrain,   ROT0, "Subsino",                          "Magic Train (Ver. 1.31)",               0 )
diff --git a/src/mame/subsino/subsino_m.cpp b/src/mame/subsino/subsino_crypt.cpp
similarity index 84%
rename from src/mame/subsino/subsino_m.cpp
rename to src/mame/subsino/subsino_crypt.cpp
index a162c503352..2e7f71e5fff 100644
--- a/src/mame/subsino/subsino_m.cpp
+++ b/src/mame/subsino/subsino_crypt.cpp
@@ -81,34 +81,14 @@ void victor21_bitswaps(uint8_t *decrypt, int i)
 
 // Decrypt:
 
-[[maybe_unused]] static void dump_decrypted(running_machine& machine, uint8_t* decrypt)
+void subsino_decrypt(uint8_t *region, void (*bitswaps)(uint8_t *decrypt, int i), const uint8_t *xors, int size)
 {
-	auto filename = "dat_" + std::string(machine.system().name);
-	auto fp = fopen(filename.c_str(), "w+b");
-	if (fp)
-	{
-		fwrite(decrypt, 0x10000, 1, fp);
-		fclose(fp);
-	}
-}
+	std::unique_ptr<uint8_t[]> decrypt = std::make_unique<uint8_t[]>(size);
 
-void subsino_decrypt(running_machine& machine, void (*bitswaps)(uint8_t *decrypt, int i), const uint8_t *xors, int size)
-{
-	std::unique_ptr<uint8_t[]> decrypt = std::make_unique<uint8_t[]>(0x10000);
-	uint8_t *const region = machine.root_device().memregion("maincpu")->base();
-
-	for (int i = 0; i < 0x10000; i++)
+	for (int i = 0; i < size; i++)
 	{
-		if (i < size)
-		{
-			decrypt[i] = region[i] ^ xors[i & 7];
-			bitswaps(decrypt.get(), i);
-		}
-		else
-		{
-			decrypt[i] = region[i];
-		}
+		decrypt[i] = region[i] ^ xors[i & 7];
+		bitswaps(decrypt.get(), i);
 	}
-//  dump_decrypted(machine, decrypt);
-	memcpy(region, decrypt.get(), 0x10000);
+	memcpy(region, decrypt.get(), size);
 }
diff --git a/src/mame/subsino/subsino_m.h b/src/mame/subsino/subsino_crypt.h
similarity index 71%
rename from src/mame/subsino/subsino_m.h
rename to src/mame/subsino/subsino_crypt.h
index ffad2f463f0..b9365fadd83 100644
--- a/src/mame/subsino/subsino_m.h
+++ b/src/mame/subsino/subsino_crypt.h
@@ -1,7 +1,7 @@
 // license:BSD-3-Clause
 // copyright-holders:Luca Elia, David Haywood, Angelo Salese, Roberto Fresca
-#ifndef MAME_SUBSINO_SUBSINO_M_H
-#define MAME_SUBSINO_SUBSINO_M_H
+#ifndef MAME_SUBSINO_SUBSINO_CRYPT_H
+#define MAME_SUBSINO_SUBSINO_CRYPT_H
 
 #pragma once
 
@@ -18,6 +18,6 @@ void tisubb_bitswaps  (uint8_t *decrypt, int i);
 void victor5_bitswaps (uint8_t *decrypt, int i);
 void victor21_bitswaps(uint8_t *decrypt, int i);
 
-void subsino_decrypt(running_machine& machine, void (*bitswaps)(uint8_t *decrypt, int i), const uint8_t *xors, int size);
+void subsino_decrypt(uint8_t *region, void (*bitswaps)(uint8_t *decrypt, int i), const uint8_t *xors, int size);
 
-#endif // MAME_SUBSINO_SUBSINO_M_H
+#endif // MAME_SUBSINO_SUBSINO_CRYPT_H