diff --git a/ld/libfiles.ntsc-beta.inc b/ld/libfiles.ntsc-beta.inc
index 2e3f57330..787ef1c9d 100644
--- a/ld/libfiles.ntsc-beta.inc
+++ b/ld/libfiles.ntsc-beta.inc
@@ -195,7 +195,7 @@
 	build/ROMID/lib/ultra/io/conteepprobe.o (section); \
 	build/ROMID/lib/ultra/io/conteepread.o (section); \
 	build/ROMID/lib/ultra/io/conteeplongread.o (section); \
-	build/ROMID/lib/lib_50480.o (section); \
+	build/ROMID/lib/ultra/io/pfsreadwritefile.o (section); \
 	build/ROMID/lib/lib_508d0.o (section); \
 	build/ROMID/lib/ultra/io/pfsfilestate.o (section); \
 	build/ROMID/lib/lib_50be0.o (section); \
diff --git a/ld/libfiles.ntsc-final.inc b/ld/libfiles.ntsc-final.inc
index d8983505f..283785d35 100644
--- a/ld/libfiles.ntsc-final.inc
+++ b/ld/libfiles.ntsc-final.inc
@@ -191,7 +191,7 @@
 	build/ROMID/lib/ultra/io/conteepprobe.o (section); \
 	build/ROMID/lib/ultra/io/conteepread.o (section); \
 	build/ROMID/lib/ultra/io/conteeplongread.o (section); \
-	build/ROMID/lib/lib_50480.o (section); \
+	build/ROMID/lib/ultra/io/pfsreadwritefile.o (section); \
 	build/ROMID/lib/lib_508d0.o (section); \
 	build/ROMID/lib/ultra/io/pfsfilestate.o (section); \
 	build/ROMID/lib/lib_50be0.o (section); \
diff --git a/ld/libfiles.pal-final.inc b/ld/libfiles.pal-final.inc
index 82341351f..eb20dffec 100644
--- a/ld/libfiles.pal-final.inc
+++ b/ld/libfiles.pal-final.inc
@@ -191,7 +191,7 @@
 	build/ROMID/lib/ultra/io/conteepprobe.o (section); \
 	build/ROMID/lib/ultra/io/conteepread.o (section); \
 	build/ROMID/lib/ultra/io/conteeplongread.o (section); \
-	build/ROMID/lib/lib_50480.o (section); \
+	build/ROMID/lib/ultra/io/pfsreadwritefile.o (section); \
 	build/ROMID/lib/lib_508d0.o (section); \
 	build/ROMID/lib/ultra/io/pfsfilestate.o (section); \
 	build/ROMID/lib/lib_50be0.o (section); \
diff --git a/src/game/pak/pak.c b/src/game/pak/pak.c
index a409124c9..d38028bcd 100644
--- a/src/game/pak/pak.c
+++ b/src/game/pak/pak.c
@@ -16,7 +16,6 @@
 #include "lib/memory.h"
 #include "lib/rng.h"
 #include "lib/lib_4e090.h"
-#include "lib/lib_50480.h"
 #include "lib/lib_513b0.h"
 #include "data.h"
 #include "types.h"
@@ -1586,7 +1585,7 @@ s32 func0f117b04(OSMesgQueue *mq, OSPfs *pfs, s32 channel)
 	return 0;
 }
 
-s32 func0f117b4c(s32 arg0, s32 arg1, u8 operation, u32 address, u32 len, u8 *buffer)
+s32 func0f117b4c(OSPfs *pfs, s32 file_no, u8 flag, u32 address, u32 len, u8 *buffer)
 {
 	u32 newaddress;
 
@@ -1594,8 +1593,8 @@ s32 func0f117b4c(s32 arg0, s32 arg1, u8 operation, u32 address, u32 len, u8 *buf
 	joyCheckPfs(2);
 #endif
 
-	if (arg0) {
-		return func00050554(arg0, arg1, operation, address, len, buffer);
+	if (pfs) {
+		return osPfsReadWriteFile(pfs, file_no, flag, address, len, buffer);
 	}
 
 	newaddress = address / 8;
@@ -1611,11 +1610,11 @@ s32 func0f117b4c(s32 arg0, s32 arg1, u8 operation, u32 address, u32 len, u8 *buf
 		return 0x80;
 	}
 
-	if (operation == OS_WRITE) {
+	if (flag == OS_WRITE) {
 		return pakWriteEeprom(newaddress, buffer, len);
 	}
 
-	if (operation == OS_READ) {
+	if (flag == OS_READ) {
 		return pakReadEeprom(newaddress, buffer, len);
 	}
 
@@ -7367,17 +7366,19 @@ glabel func0f11a434
 //	var800a2380[device].unk2b4 = -1;
 //}
 
-s32 func0f11a504(s8 arg0, s32 arg1, s32 arg2, u8 operation, u32 address, u32 len, u8 *buffer)
+s32 func0f11a504(s8 device, OSPfs *pfs, s32 file_no, u8 flag, u32 address, u32 len, u8 *buffer)
 {
 	s32 result;
-	len = func0f1165f8(arg0, len);
+	len = func0f1165f8(device, len);
 
 #if VERSION >= VERSION_NTSC_1_0
 	joy000150e8();
 #else
 	joy000150e8(3096, "pak.c");
 #endif
-	result = func0f117b4c(arg1, arg2, operation, address, len, buffer);
+
+	result = func0f117b4c(pfs, file_no, flag, address, len, buffer);
+
 #if VERSION >= VERSION_NTSC_1_0
 	joy00015144();
 #else
diff --git a/src/include/PR/os_pfs.h b/src/include/PR/os_pfs.h
index e4695bb59..8f9afef92 100644
--- a/src/include/PR/os_pfs.h
+++ b/src/include/PR/os_pfs.h
@@ -100,6 +100,7 @@ typedef struct {
 #define PFS_LABEL_AREA          7
 #define PFS_INODE_SIZE_PER_PAGE 128
 #define PFS_PAGE_NOT_USED       3
+#define PFS_WRITTEN             2
 #define PFS_PAGE_SIZE           (BLOCKSIZE * PFS_ONE_PAGE)
 
 #define PFS_READ                0
@@ -159,6 +160,7 @@ s32 osPfsAllocateFile(OSPfs *pfs, u16 company_code, u32 game_code, char *game_na
 s32 osPfsFindFile(OSPfs *pfs, u16 company_code, u32 game_code, char *game_name, char *ext_name, s32 *file_no);
 s32 osPfsDeleteFile(OSPfs *pfs, u16 company_code, u32 game_code, char *game_name, char *ext_name);
 s32 osPfsFileState(OSPfs *pfs, s32 file_no, OSPfsState *state);
+s32 osPfsReadWriteFile(OSPfs* pfs, s32 fileNo, u8 flag, s32 offset, s32 size, u8* data);
 
 s32 osMotorAccess(OSPfs *pfs, u32 vibrate);
 void osSetUpMempakWrite(s32 channel, OSPifRam* buf);
diff --git a/src/include/game/pak/pak.h b/src/include/game/pak/pak.h
index 4990422bf..2478fc5d3 100644
--- a/src/include/game/pak/pak.h
+++ b/src/include/game/pak/pak.h
@@ -5,7 +5,7 @@
 #include "types.h"
 
 u32 func0f1165d0(s8 device);
-u32 func0f1165f8(s8 arg0, u32 arg1);
+u32 func0f1165f8(s8 device, u32 arg1);
 u32 func0f116658(s8 arg0, u32 arg1);
 u32 func0f116684(u32 arg0);
 u32 func0f11668c(s8 device);
@@ -48,7 +48,7 @@ s32 func0f117b04(OSMesgQueue *mq, OSPfs *pfs, s32 channel, s32 *arg3);
 s32 func0f117b04(OSMesgQueue *mq, OSPfs *pfs, s32 channel);
 #endif
 
-s32 func0f117b4c(s32 arg0, s32 arg1, u8 operation, u32 address, u32 len, u8 *buffer);
+s32 func0f117b4c(OSPfs *pfs, s32 file_no, u8 flag, u32 address, u32 len, u8 *buffer);
 s32 func0f117c0c(s32 arg0, s32 *arg1, s32 *arg2);
 s32 func0f117c80(OSPfs *pfs, s32 *arg1);
 s32 func0f117ce4(OSPfs *pfs, s32 file_no, OSPfsState *note);
@@ -85,7 +85,7 @@ u32 func0f11a1d0(void);
 void func0f11a2e4(void);
 void func0f11a32c(s8 device, u8 arg1, u32 line, char *file);
 void func0f11a434(s8 arg0);
-s32 func0f11a504(s8 arg0, s32 arg1, s32 arg2, u8 operation, u32 address, u32 len, u8 *buffer);
+s32 func0f11a504(s8 device, OSPfs *pfs, s32 file_no, u8 flag, u32 address, u32 len, u8 *buffer);
 s32 func0f11a574(s8 device);
 u32 func0f11a7dc(void);
 u32 func0f11a8f4(void);
diff --git a/src/include/lib/lib_50480.h b/src/include/lib/lib_50480.h
deleted file mode 100644
index a86f21fe1..000000000
--- a/src/include/lib/lib_50480.h
+++ /dev/null
@@ -1,9 +0,0 @@
-#ifndef _IN_LIB_LIB_50480_H
-#define _IN_LIB_LIB_50480_H
-#include <ultra64.h>
-#include "data.h"
-#include "types.h"
-
-s32 func00050554(s32 arg0, s32 arg1, u8 operation, u32 address, u32 len, u8 *buffer);
-
-#endif
diff --git a/src/lib/lib_50480.c b/src/lib/lib_50480.c
deleted file mode 100644
index 2c0516e75..000000000
--- a/src/lib/lib_50480.c
+++ /dev/null
@@ -1,297 +0,0 @@
-#include <ultra64.h>
-#include "libultra_internal.h"
-#include "constants.h"
-#include "bss.h"
-#include "lib/lib_50480.h"
-#include "data.h"
-#include "types.h"
-
-#define CHECK_IPAGE(p, pfs)                                                                                   \
-	(((p).ipage >= (pfs).inode_start_page) && ((p).inode_t.bank < (pfs).banks) && ((p).inode_t.page >= 0x01) && \
-	 ((p).inode_t.page < 0x80))
-
-s32 __osPfsGetNextPage(OSPfs *pfs, u8 *bank, __OSInode *inode, __OSInodeUnit *page)
-{
-	s32 ret;
-
-	if (page->inode_t.bank != *bank) {
-		*bank = page->inode_t.bank;
-
-		if ((ret = __osPfsRWInode(pfs, inode, PFS_READ, *bank)) != 0) {
-			return ret;
-		}
-	}
-
-	*page = inode->inode_page[page->inode_t.page];
-
-	if (!CHECK_IPAGE(*page, *pfs)) {
-		if (page->ipage == 1) {
-			return PFS_ERR_INVALID;
-		}
-
-		return PFS_ERR_INCONSISTENT;
-	}
-
-	return 0;
-}
-
-GLOBAL_ASM(
-glabel func00050554
-/*    50554:	27bdfe90 */ 	addiu	$sp,$sp,-368
-/*    50558:	afbf002c */ 	sw	$ra,0x2c($sp)
-/*    5055c:	afb30028 */ 	sw	$s3,0x28($sp)
-/*    50560:	afb20024 */ 	sw	$s2,0x24($sp)
-/*    50564:	afb10020 */ 	sw	$s1,0x20($sp)
-/*    50568:	afb0001c */ 	sw	$s0,0x1c($sp)
-/*    5056c:	afa60178 */ 	sw	$a2,0x178($sp)
-/*    50570:	8c8e0050 */ 	lw	$t6,0x50($a0)
-/*    50574:	30d000ff */ 	andi	$s0,$a2,0xff
-/*    50578:	00e08825 */ 	or	$s1,$a3,$zero
-/*    5057c:	00ae082a */ 	slt	$at,$a1,$t6
-/*    50580:	10200003 */ 	beqz	$at,.L00050590
-/*    50584:	00809025 */ 	or	$s2,$a0,$zero
-/*    50588:	04a10003 */ 	bgez	$a1,.L00050598
-/*    5058c:	8fa20180 */ 	lw	$v0,0x180($sp)
-.L00050590:
-/*    50590:	100000c7 */ 	b	.L000508b0
-/*    50594:	24020005 */ 	addiu	$v0,$zero,0x5
-.L00050598:
-/*    50598:	18400003 */ 	blez	$v0,.L000505a8
-/*    5059c:	304f001f */ 	andi	$t7,$v0,0x1f
-/*    505a0:	11e00003 */ 	beqz	$t7,.L000505b0
-/*    505a4:	00000000 */ 	nop
-.L000505a8:
-/*    505a8:	100000c1 */ 	b	.L000508b0
-/*    505ac:	24020005 */ 	addiu	$v0,$zero,0x5
-.L000505b0:
-/*    505b0:	06200003 */ 	bltz	$s1,.L000505c0
-/*    505b4:	3238001f */ 	andi	$t8,$s1,0x1f
-/*    505b8:	53000004 */ 	beqzl	$t8,.L000505cc
-/*    505bc:	8e590000 */ 	lw	$t9,0x0($s2)
-.L000505c0:
-/*    505c0:	100000bb */ 	b	.L000508b0
-/*    505c4:	24020005 */ 	addiu	$v0,$zero,0x5
-/*    505c8:	8e590000 */ 	lw	$t9,0x0($s2)
-.L000505cc:
-/*    505cc:	02402025 */ 	or	$a0,$s2,$zero
-/*    505d0:	33280001 */ 	andi	$t0,$t9,0x1
-/*    505d4:	15000003 */ 	bnez	$t0,.L000505e4
-/*    505d8:	00000000 */ 	nop
-/*    505dc:	100000b4 */ 	b	.L000508b0
-/*    505e0:	24020005 */ 	addiu	$v0,$zero,0x5
-.L000505e4:
-/*    505e4:	0c013218 */ 	jal	__osCheckId
-/*    505e8:	afa50174 */ 	sw	$a1,0x174($sp)
-/*    505ec:	24010002 */ 	addiu	$at,$zero,0x2
-/*    505f0:	54410004 */ 	bnel	$v0,$at,.L00050604
-/*    505f4:	92490065 */ 	lbu	$t1,0x65($s2)
-/*    505f8:	100000ad */ 	b	.L000508b0
-/*    505fc:	24020002 */ 	addiu	$v0,$zero,0x2
-/*    50600:	92490065 */ 	lbu	$t1,0x65($s2)
-.L00050604:
-/*    50604:	02402025 */ 	or	$a0,$s2,$zero
-/*    50608:	51200008 */ 	beqzl	$t1,.L0005062c
-/*    5060c:	8e4a005c */ 	lw	$t2,0x5c($s2)
-/*    50610:	0c013378 */ 	jal	__osPfsSelectBank
-/*    50614:	00002825 */ 	or	$a1,$zero,$zero
-/*    50618:	50400004 */ 	beqzl	$v0,.L0005062c
-/*    5061c:	8e4a005c */ 	lw	$t2,0x5c($s2)
-/*    50620:	100000a4 */ 	b	.L000508b4
-/*    50624:	8fbf002c */ 	lw	$ra,0x2c($sp)
-/*    50628:	8e4a005c */ 	lw	$t2,0x5c($s2)
-.L0005062c:
-/*    5062c:	8fab0174 */ 	lw	$t3,0x174($sp)
-/*    50630:	8e440004 */ 	lw	$a0,0x4($s2)
-/*    50634:	8e450008 */ 	lw	$a1,0x8($s2)
-/*    50638:	014b3021 */ 	addu	$a2,$t2,$t3
-/*    5063c:	30ccffff */ 	andi	$t4,$a2,0xffff
-/*    50640:	01803025 */ 	or	$a2,$t4,$zero
-/*    50644:	0c012e18 */ 	jal	__osContRamRead
-/*    50648:	27a7014c */ 	addiu	$a3,$sp,0x14c
-/*    5064c:	10400003 */ 	beqz	$v0,.L0005065c
-/*    50650:	97ad0150 */ 	lhu	$t5,0x150($sp)
-/*    50654:	10000097 */ 	b	.L000508b4
-/*    50658:	8fbf002c */ 	lw	$ra,0x2c($sp)
-.L0005065c:
-/*    5065c:	11a00003 */ 	beqz	$t5,.L0005066c
-/*    50660:	8fae014c */ 	lw	$t6,0x14c($sp)
-/*    50664:	15c00003 */ 	bnez	$t6,.L00050674
-/*    50668:	97af0152 */ 	lhu	$t7,0x152($sp)
-.L0005066c:
-/*    5066c:	10000090 */ 	b	.L000508b0
-/*    50670:	24020005 */ 	addiu	$v0,$zero,0x5
-.L00050674:
-/*    50674:	8e580060 */ 	lw	$t8,0x60($s2)
-/*    50678:	93b90152 */ 	lbu	$t9,0x152($sp)
-/*    5067c:	97aa0152 */ 	lhu	$t2,0x152($sp)
-/*    50680:	01f8082a */ 	slt	$at,$t7,$t8
-/*    50684:	5420000a */ 	bnezl	$at,.L000506b0
-/*    50688:	24010001 */ 	addiu	$at,$zero,0x1
-/*    5068c:	92480064 */ 	lbu	$t0,0x64($s2)
-/*    50690:	93a90153 */ 	lbu	$t1,0x153($sp)
-/*    50694:	0328082a */ 	slt	$at,$t9,$t0
-/*    50698:	50200005 */ 	beqzl	$at,.L000506b0
-/*    5069c:	24010001 */ 	addiu	$at,$zero,0x1
-/*    506a0:	19200002 */ 	blez	$t1,.L000506ac
-/*    506a4:	29210080 */ 	slti	$at,$t1,0x80
-/*    506a8:	14200007 */ 	bnez	$at,.L000506c8
-.L000506ac:
-/*    506ac:	24010001 */ 	addiu	$at,$zero,0x1
-.L000506b0:
-/*    506b0:	15410003 */ 	bne	$t2,$at,.L000506c0
-/*    506b4:	00000000 */ 	nop
-/*    506b8:	1000007d */ 	b	.L000508b0
-/*    506bc:	24020005 */ 	addiu	$v0,$zero,0x5
-.L000506c0:
-/*    506c0:	1000007b */ 	b	.L000508b0
-/*    506c4:	24020003 */ 	addiu	$v0,$zero,0x3
-.L000506c8:
-/*    506c8:	16000007 */ 	bnez	$s0,.L000506e8
-/*    506cc:	afb00034 */ 	sw	$s0,0x34($sp)
-/*    506d0:	93ac0154 */ 	lbu	$t4,0x154($sp)
-/*    506d4:	318d0002 */ 	andi	$t5,$t4,0x2
-/*    506d8:	55a00004 */ 	bnezl	$t5,.L000506ec
-/*    506dc:	97af0152 */ 	lhu	$t7,0x152($sp)
-/*    506e0:	10000073 */ 	b	.L000508b0
-/*    506e4:	24020006 */ 	addiu	$v0,$zero,0x6
-.L000506e8:
-/*    506e8:	97af0152 */ 	lhu	$t7,0x152($sp)
-.L000506ec:
-/*    506ec:	240e00ff */ 	addiu	$t6,$zero,0xff
-/*    506f0:	a3ae003b */ 	sb	$t6,0x3b($sp)
-/*    506f4:	06210003 */ 	bgez	$s1,.L00050704
-/*    506f8:	00111143 */ 	sra	$v0,$s1,0x5
-/*    506fc:	2621001f */ 	addiu	$at,$s1,0x1f
-/*    50700:	00011143 */ 	sra	$v0,$at,0x5
-.L00050704:
-/*    50704:	28410008 */ 	slti	$at,$v0,0x8
-/*    50708:	00408025 */ 	or	$s0,$v0,$zero
-/*    5070c:	1420000d */ 	bnez	$at,.L00050744
-/*    50710:	a7af0048 */ 	sh	$t7,0x48($sp)
-/*    50714:	02402025 */ 	or	$a0,$s2,$zero
-.L00050718:
-/*    50718:	27a5003b */ 	addiu	$a1,$sp,0x3b
-/*    5071c:	27a6004c */ 	addiu	$a2,$sp,0x4c
-/*    50720:	0c014120 */ 	jal	__osPfsGetNextPage
-/*    50724:	27a70048 */ 	addiu	$a3,$sp,0x48
-/*    50728:	10400003 */ 	beqz	$v0,.L00050738
-/*    5072c:	2610fff8 */ 	addiu	$s0,$s0,-8
-/*    50730:	10000060 */ 	b	.L000508b4
-/*    50734:	8fbf002c */ 	lw	$ra,0x2c($sp)
-.L00050738:
-/*    50738:	2a010008 */ 	slti	$at,$s0,0x8
-/*    5073c:	5020fff6 */ 	beqzl	$at,.L00050718
-/*    50740:	02402025 */ 	or	$a0,$s2,$zero
-.L00050744:
-/*    50744:	8fa20180 */ 	lw	$v0,0x180($sp)
-/*    50748:	8fb10184 */ 	lw	$s1,0x184($sp)
-/*    5074c:	04410003 */ 	bgez	$v0,.L0005075c
-/*    50750:	0002c143 */ 	sra	$t8,$v0,0x5
-/*    50754:	2441001f */ 	addiu	$at,$v0,0x1f
-/*    50758:	0001c143 */ 	sra	$t8,$at,0x5
-.L0005075c:
-/*    5075c:	1b000031 */ 	blez	$t8,.L00050824
-/*    50760:	03009825 */ 	or	$s3,$t8,$zero
-.L00050764:
-/*    50764:	24010008 */ 	addiu	$at,$zero,0x8
-/*    50768:	16010009 */ 	bne	$s0,$at,.L00050790
-/*    5076c:	02402025 */ 	or	$a0,$s2,$zero
-/*    50770:	27a5003b */ 	addiu	$a1,$sp,0x3b
-/*    50774:	27a6004c */ 	addiu	$a2,$sp,0x4c
-/*    50778:	0c014120 */ 	jal	__osPfsGetNextPage
-/*    5077c:	27a70048 */ 	addiu	$a3,$sp,0x48
-/*    50780:	10400003 */ 	beqz	$v0,.L00050790
-/*    50784:	00008025 */ 	or	$s0,$zero,$zero
-/*    50788:	1000004a */ 	b	.L000508b4
-/*    5078c:	8fbf002c */ 	lw	$ra,0x2c($sp)
-.L00050790:
-/*    50790:	93b90048 */ 	lbu	$t9,0x48($sp)
-/*    50794:	92480065 */ 	lbu	$t0,0x65($s2)
-/*    50798:	02402025 */ 	or	$a0,$s2,$zero
-/*    5079c:	53280008 */ 	beql	$t9,$t0,.L000507c0
-/*    507a0:	93a90049 */ 	lbu	$t1,0x49($sp)
-/*    507a4:	0c013378 */ 	jal	__osPfsSelectBank
-/*    507a8:	03202825 */ 	or	$a1,$t9,$zero
-/*    507ac:	50400004 */ 	beqzl	$v0,.L000507c0
-/*    507b0:	93a90049 */ 	lbu	$t1,0x49($sp)
-/*    507b4:	1000003f */ 	b	.L000508b4
-/*    507b8:	8fbf002c */ 	lw	$ra,0x2c($sp)
-/*    507bc:	93a90049 */ 	lbu	$t1,0x49($sp)
-.L000507c0:
-/*    507c0:	8fac0034 */ 	lw	$t4,0x34($sp)
-/*    507c4:	02203825 */ 	or	$a3,$s1,$zero
-/*    507c8:	000950c0 */ 	sll	$t2,$t1,0x3
-/*    507cc:	01503021 */ 	addu	$a2,$t2,$s0
-/*    507d0:	30cbffff */ 	andi	$t3,$a2,0xffff
-/*    507d4:	15800007 */ 	bnez	$t4,.L000507f4
-/*    507d8:	01603025 */ 	or	$a2,$t3,$zero
-/*    507dc:	8e440004 */ 	lw	$a0,0x4($s2)
-/*    507e0:	8e450008 */ 	lw	$a1,0x8($s2)
-/*    507e4:	0c012e18 */ 	jal	__osContRamRead
-/*    507e8:	02203825 */ 	or	$a3,$s1,$zero
-/*    507ec:	10000006 */ 	b	.L00050808
-/*    507f0:	00401825 */ 	or	$v1,$v0,$zero
-.L000507f4:
-/*    507f4:	8e440004 */ 	lw	$a0,0x4($s2)
-/*    507f8:	8e450008 */ 	lw	$a1,0x8($s2)
-/*    507fc:	0c012d84 */ 	jal	__osContRamWrite
-/*    50800:	afa00010 */ 	sw	$zero,0x10($sp)
-/*    50804:	00401825 */ 	or	$v1,$v0,$zero
-.L00050808:
-/*    50808:	10400003 */ 	beqz	$v0,.L00050818
-/*    5080c:	26310020 */ 	addiu	$s1,$s1,0x20
-/*    50810:	10000027 */ 	b	.L000508b0
-/*    50814:	00601025 */ 	or	$v0,$v1,$zero
-.L00050818:
-/*    50818:	2673ffff */ 	addiu	$s3,$s3,-1
-/*    5081c:	1660ffd1 */ 	bnez	$s3,.L00050764
-/*    50820:	26100001 */ 	addiu	$s0,$s0,0x1
-.L00050824:
-/*    50824:	8fad0034 */ 	lw	$t5,0x34($sp)
-/*    50828:	93a20154 */ 	lbu	$v0,0x154($sp)
-/*    5082c:	24010001 */ 	addiu	$at,$zero,0x1
-/*    50830:	15a1001c */ 	bne	$t5,$at,.L000508a4
-/*    50834:	304e0002 */ 	andi	$t6,$v0,0x2
-/*    50838:	15c0001a */ 	bnez	$t6,.L000508a4
-/*    5083c:	344f0002 */ 	ori	$t7,$v0,0x2
-/*    50840:	a3af0154 */ 	sb	$t7,0x154($sp)
-/*    50844:	92580065 */ 	lbu	$t8,0x65($s2)
-/*    50848:	02402025 */ 	or	$a0,$s2,$zero
-/*    5084c:	53000008 */ 	beqzl	$t8,.L00050870
-/*    50850:	8e48005c */ 	lw	$t0,0x5c($s2)
-/*    50854:	0c013378 */ 	jal	__osPfsSelectBank
-/*    50858:	00002825 */ 	or	$a1,$zero,$zero
-/*    5085c:	50400004 */ 	beqzl	$v0,.L00050870
-/*    50860:	8e48005c */ 	lw	$t0,0x5c($s2)
-/*    50864:	10000013 */ 	b	.L000508b4
-/*    50868:	8fbf002c */ 	lw	$ra,0x2c($sp)
-/*    5086c:	8e48005c */ 	lw	$t0,0x5c($s2)
-.L00050870:
-/*    50870:	8fb90174 */ 	lw	$t9,0x174($sp)
-/*    50874:	8e440004 */ 	lw	$a0,0x4($s2)
-/*    50878:	8e450008 */ 	lw	$a1,0x8($s2)
-/*    5087c:	01193021 */ 	addu	$a2,$t0,$t9
-/*    50880:	30c9ffff */ 	andi	$t1,$a2,0xffff
-/*    50884:	01203025 */ 	or	$a2,$t1,$zero
-/*    50888:	afa00010 */ 	sw	$zero,0x10($sp)
-/*    5088c:	0c012d84 */ 	jal	__osContRamWrite
-/*    50890:	27a7014c */ 	addiu	$a3,$sp,0x14c
-/*    50894:	50400004 */ 	beqzl	$v0,.L000508a8
-/*    50898:	8e440004 */ 	lw	$a0,0x4($s2)
-/*    5089c:	10000005 */ 	b	.L000508b4
-/*    508a0:	8fbf002c */ 	lw	$ra,0x2c($sp)
-.L000508a4:
-/*    508a4:	8e440004 */ 	lw	$a0,0x4($s2)
-.L000508a8:
-/*    508a8:	0c012ea4 */ 	jal	__osPfsGetStatus
-/*    508ac:	8e450008 */ 	lw	$a1,0x8($s2)
-.L000508b0:
-/*    508b0:	8fbf002c */ 	lw	$ra,0x2c($sp)
-.L000508b4:
-/*    508b4:	8fb0001c */ 	lw	$s0,0x1c($sp)
-/*    508b8:	8fb10020 */ 	lw	$s1,0x20($sp)
-/*    508bc:	8fb20024 */ 	lw	$s2,0x24($sp)
-/*    508c0:	8fb30028 */ 	lw	$s3,0x28($sp)
-/*    508c4:	03e00008 */ 	jr	$ra
-/*    508c8:	27bd0170 */ 	addiu	$sp,$sp,0x170
-);
diff --git a/src/lib/lib_508d0.c b/src/lib/lib_508d0.c
index c37872e64..04a06e5d1 100644
--- a/src/lib/lib_508d0.c
+++ b/src/lib/lib_508d0.c
@@ -2,7 +2,6 @@
 #include "libultra_internal.h"
 #include "constants.h"
 #include "bss.h"
-#include "lib/lib_50480.h"
 #include "data.h"
 #include "types.h"
 
diff --git a/src/lib/ultra/io/pfsreadwritefile.c b/src/lib/ultra/io/pfsreadwritefile.c
new file mode 100644
index 000000000..784c81a91
--- /dev/null
+++ b/src/lib/ultra/io/pfsreadwritefile.c
@@ -0,0 +1,151 @@
+#include <ultra64.h>
+#include "libultra_internal.h"
+#include "constants.h"
+#include "bss.h"
+#include "data.h"
+#include "types.h"
+
+#define CHECK_IPAGE(p, pfs)                                                                                   \
+	(((p).ipage >= (pfs).inode_start_page) && ((p).inode_t.bank < (pfs).banks) && ((p).inode_t.page >= 0x01) && \
+	 ((p).inode_t.page < 0x80))
+
+s32 __osPfsGetNextPage(OSPfs *pfs, u8 *bank, __OSInode *inode, __OSInodeUnit *page)
+{
+	s32 ret;
+
+	if (page->inode_t.bank != *bank) {
+		*bank = page->inode_t.bank;
+
+		if ((ret = __osPfsRWInode(pfs, inode, PFS_READ, *bank)) != 0) {
+			return ret;
+		}
+	}
+
+	*page = inode->inode_page[page->inode_t.page];
+
+	if (!CHECK_IPAGE(*page, *pfs)) {
+		if (page->ipage == 1) {
+			return PFS_ERR_INVALID;
+		}
+
+		return PFS_ERR_INCONSISTENT;
+	}
+
+	return 0;
+}
+
+s32 osPfsReadWriteFile(OSPfs* pfs, s32 fileNo, u8 flag, s32 offset, s32 size, u8* data)
+{
+	s32 ret;
+	__OSDir dir;
+	__OSInode inode;
+	__OSInodeUnit curPage;
+	s32 curBlock;
+	s32 blockSize;
+	u8* buffer;
+	u8 bank;
+	u16 blockno;
+
+	if (fileNo >= pfs->dir_size || fileNo < 0) {
+		return PFS_ERR_INVALID;
+	}
+
+	if (size <= 0 || (size % BLOCKSIZE) != 0) {
+		return PFS_ERR_INVALID;
+	}
+
+	if (offset < 0 || (offset % BLOCKSIZE) != 0) {
+		return PFS_ERR_INVALID;
+	}
+
+	if (!(pfs->status & PFS_INITIALIZED)) {
+		return PFS_ERR_INVALID;
+	}
+
+	if (__osCheckId(pfs) == PFS_ERR_NEW_PACK) {
+		return PFS_ERR_NEW_PACK;
+	}
+
+	if (pfs->activebank != 0 && (ret = __osPfsSelectBank(pfs, 0)) != 0) {
+		return ret;
+	}
+
+	if ((ret = __osContRamRead(pfs->queue, pfs->channel, pfs->dir_table + fileNo, (u8*)&dir)) != 0) {
+		return ret;
+	}
+
+	if (dir.company_code == 0 || dir.game_code == 0) {
+		return PFS_ERR_INVALID;
+	}
+
+	if (!CHECK_IPAGE(dir.start_page, *pfs)) {
+		if (dir.start_page.ipage == 1) {
+			return PFS_ERR_INVALID;
+		}
+
+		return PFS_ERR_INCONSISTENT;
+	}
+
+	if (flag == PFS_READ && ((dir.status & PFS_WRITTEN) == 0)) {
+		return PFS_ERR_BAD_DATA;
+	}
+
+	bank = 255;
+	curBlock = offset / BLOCKSIZE;
+	curPage = dir.start_page;
+
+	while (curBlock >= 8) {
+		if ((ret = __osPfsGetNextPage(pfs, &bank, &inode, &curPage)) != 0) {
+			return ret;
+		}
+
+		curBlock -= 8;
+	}
+
+	blockSize = size / BLOCKSIZE;
+	buffer = data;
+
+	while (blockSize > 0) {
+		if (curBlock == 8) {
+			if ((ret = __osPfsGetNextPage(pfs, &bank, &inode, &curPage)) != 0) {
+				return ret;
+			}
+
+			curBlock = 0;
+		}
+
+		if (pfs->activebank != curPage.inode_t.bank && (ret = __osPfsSelectBank(pfs, curPage.inode_t.bank)) != 0) {
+			return ret;
+		}
+
+		blockno = curPage.inode_t.page * PFS_ONE_PAGE + curBlock;
+
+		if (flag == PFS_READ) {
+			ret = __osContRamRead(pfs->queue, pfs->channel, blockno, buffer);
+		} else {
+			ret = __osContRamWrite(pfs->queue, pfs->channel, blockno, buffer, 0);
+		}
+
+		if (ret != 0) {
+			return ret;
+		}
+
+		buffer += BLOCKSIZE;
+		curBlock++;
+		blockSize--;
+	}
+
+	if (flag == PFS_WRITE && !(dir.status & PFS_WRITTEN)) {
+		dir.status |= PFS_WRITTEN;
+
+		if (pfs->activebank != 0 && (ret = __osPfsSelectBank(pfs, 0)) != 0) {
+			return ret;
+		}
+
+		if ((ret = __osContRamWrite(pfs->queue, pfs->channel, pfs->dir_table + fileNo, (u8*)&dir, 0)) != 0) {
+			return ret;
+		}
+	}
+
+	return __osPfsGetStatus(pfs->queue, pfs->channel);
+}