HD-AE5000 Custom Filesystem

The HD-AE5000 extension board uses a completely custom, proprietary filesystem – not FAT, ext2, or any industry standard. Despite one error string in the ROM mentioning “FAT read error,” no FAT boot sector signatures (0x55AA, 0xEB), FAT12/FAT16/FAT32 identifier strings, or standard FAT data structures exist anywhere in the firmware. The firmware was authored by M. Kitajima (Technics/Panasonic), dated Juli-Oktober 1996.

Hardware

The filesystem operates on the following hardware:

Component Details
Storage Medium 2.5” IDE Hard Disk (1.08GB capacity)
PC Interface NEC uPD71055 (i8255-compatible) PPI for parallel port communication
Static RAM 512KB (2x 256KB) at 0x200000-0x27FFFF
ROM 512KB at 0x280000-0x2FFFFF
ATA Registers 0x130010-0x130020
Addressing Mode CHS (Cylinder/Head/Sector) – not LBA

ATA Commands Used

Command Code Description
READ SECTORS 0x20 Read one or more sectors from disk
WRITE SECTORS 0x30 Write one or more sectors to disk
STANDBY 0x94 Spin down the drive motor
IDENTIFY DEVICE 0xEC Query drive geometry and capabilities

Three-Level Block Hierarchy (FSB/FGB/FEB)

The filesystem organizes data using three custom block types arranged in a hierarchy:

FSB (File System Block)
 +-- Master metadata for the entire filesystem
 |
 +-- FGB (File Group Block)
 |    +-- Groups files together (directory-like container)
 |    |
 |    +-- FEB (File Entry Block)
 |    |    +-- Individual file metadata
 |    +-- FEB
 |    +-- ...
 |
 +-- FGB
 |    +-- FEB
 |    +-- ...
 +-- ...

FSB (File System Block)

The FSB is the master metadata structure for the entire filesystem. There is one FSB per formatted disk. It is serialized across multiple on-disk sectors:

Operation Address Size Role
HDAE5000_FS_Read_FSB 0x287F55 832 bytes Display UI initialization (reads from RAM, not disk)
HDAE5000_FS_Write_FSB 0x288295 5,072 bytes Serializes in-RAM state to disk sectors
HDAE5000_Cmd03_ReadFSB 0x2959F6 838 bytes Reads FSB sectors from disk (PPORT interface)
HDAE5000_Cmd06_WriteFSB 0x296294 150 bytes Writes FSB sectors to disk (PPORT interface)

The FSB can be transferred to/from a PC via the parallel port interface (PPORT commands 03-06), enabling backup and management through the HD-TechManager5000 Windows software.

FSB On-Disk Sector Layout

HDAE5000_FS_Write_FSB serializes the FSB across multiple sectors:

Sector 0 (32 bytes, staging buffer at 0x22A058):

  • Header fields from ROM template at 0x2E2EAC
  • VarInt-encoded directory entry count
  • Display layout metadata

Sector 1 (16 directory entries, staging buffer at 0x22B020):

  • 16 entries at stride 37 bytes (0x25) each
  • Total: 592 bytes per sector

Sector 2 (16 bytes, staging buffer at 0x22A078):

  • VarInt-encoded current selection/position index
  • Display cell reference data

Sectors 3-4: Additional navigation and index data.

The FSB supports 5 pages of 24 entries = 120 total directory slots, with the page selector at 0x23A090 stepping in increments of 24 (values 0, 24, 48, 72, 96).

21-Byte In-RAM Directory Entry (at 0x22A2CA)

HDAE5000_FS_Read_FSB initializes 24 entries from a ROM template at 0x2E2E60:

Offset  Size  Contents
------  ----  --------
0x00    4     Header (flags/state, first 4 bytes not copied to display tile)
0x04    16    Display tile block (copied to screen for rendering)
0x14    1     Terminator (0x09 = tab character)

ROM template contents: 20 20 20 3A 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 09 = " : " + 0x09 terminator. The colon at byte 3 separates an entry number field from the name field.

37-Byte On-Disk Directory Entry (at 0x22B020)

HDAE5000_FS_Write_FSB serializes entries using a 37-byte format from ROM template at 0x2E2EC0:

Offset  Size  Contents
------  ----  --------
0x00    35    Name/descriptor string (from template: ":" + 33 spaces + 0x09)
0x20    1     Flag byte 1 (0x2A = '*' if flagged, else 0x20 = space)
0x21    2     Sector allocation index (16-bit)
0x23    1     Flag byte 2 (0x2A = '*' if flagged, else 0x20 = space)
0x24    1     Padding / display cell reference

ROM template contents: 3A + 33x20 + 09 00 25 = ":" + spaces + terminator.

FGB (File Group Block)

FGBs function as directory-like containers, grouping related files together within a partition. Their exact on-disk layout is embedded within the sector data read by HDAE5000_Cmd03_ReadFSB, which uses 9 region descriptors to address different parts of the filesystem. Each region descriptor is a 32-bit sector address.

FEB (File Entry Block)

FEBs contain individual file metadata for each stored file on the disk. They are accessed through HDAE5000_FS_Entry_Lookup (0x28A2F0) using the 9-byte directory entry format described below.

Partition System

The filesystem supports a structured partition layout:

  • Up to 16 partitions per disk
  • Up to 40 directory entries per partition (9 bytes each, insertion-sorted by name)
  • Partition status byte: 0x02 = active partition

9-Byte Directory Entry (at 0x230884)

Each partition maintains up to 40 directory entries at RAM 0x230884 (360 bytes total). Entries are insertion-sorted by name. Each 9-byte entry contains handler indices used by HDAE5000_FS_Entry_Lookup to dispatch through the function pointer table at ROM 0x2E1E14:

Offset  Size  Contents
------  ----  --------
0x00    1     Handler index 0 (file type / operation code)
0x01    1     Handler index 1 (secondary type / flags)
0x02    1     Handler index 2 (display cell reference)
0x03    1     Handler index 3 (slot index, used with CHS params at 0x23A092-0x23A094)
0x04    2     Source address / sector reference (16-bit)
0x06    1     Status / protection flags
0x07    2     Sector count or size (16-bit)

Each handler index byte is used as a *4 offset into the ROM function pointer table at 0x2E1E14, selecting the appropriate display/operation callback.

Sector Allocation

Sector allocation uses a custom variable-length integer encoding scheme:

VarInt Encoding

Sizes and offsets are encoded using 7-bit variable-length integers (VarInt) where bit 7 is a continuation flag. This is similar to the encoding used in Protocol Buffers and MIDI:

  • If bit 7 is clear (0), this is the last byte of the value
  • If bit 7 is set (1), more bytes follow
  • Each byte contributes 7 bits of data
Routine Address
HDAE5000_VarInt_Encode 0x28F36B
HDAE5000_VarInt_Decode 0x28F3BD

Sector Table

  • Stored in RAM at 0x22B430 (20KB = 0x5000 bytes buffer)
  • Free space calculated by scanning 4-byte groups, clearing bit 7, shift-left by 7
  • Maximum sector number: 20,457 (0x4FE9)
  • Per-sector metadata at offsets from table base:
    • table[sector + 22]: sector type byte (0xFF = free)
    • table[sector + 23]: file type code (0x2F = invalid/reserved)

RAM Data Structures

The filesystem maintains several data structures in RAM, organized by functional group:

ATA/CHS Parameters (from IDENTIFY command)

Address Size Purpose
0x229D99 word ATA IDENTIFY: Cylinders (CHS geometry)
0x229D9A word ATA IDENTIFY: Heads (CHS geometry)
0x229DAD byte Content type 1 (for HDAE5000_File_Save type code dispatch)
0x229DAE byte Content type 2 (for HDAE5000_File_Save type code dispatch)

CHS Spinbox UI State

Address Size Purpose
0x22AA4C dword Current CHS context pointer (0x007F01xx range)
0x22AA4E-0x22AA57 10 bytes Spinbox state bytes (one per event handler sub-routine in HDAE5000_FS_Init)
0x22AA5C word Current input state (0-5 for CHS digit selection)
0x22AA5E word Current cylinder value
0x22AA60 word Current head value

FSB Display & Write Buffers

Address Size Purpose
0x22A058 32 bytes FSB Sector 0 output buffer (header + entry count)
0x22A078 16 bytes FSB Sector 2 output buffer (position/selection)
0x22A2CA 504 bytes FSB display buffer: 24 x 21-byte entries (4-byte header + 16-byte tile + 1-byte terminator)
0x22AA9C varies Filesystem buffer base – up to 20 entries
0x22B020 varies FSB write staging area (16 x 37-byte entries)
0x22B272 word Sector allocation index / column counter

Sector Allocation Table

Address Size Purpose
0x22B430 20KB (0x5000) Sector allocation table – descriptor at table[sector + 22]
0x22B43C varies Sector metadata (bytes per sector)
0x23085E word Bytes consumed by last VarInt decode (set by HDAE5000_Calc_Disk_Space)

File Operation State (0x2304xx)

Address Size Purpose Routines
0x230430 word Current file type code (from sector table) HDAE5000_File_Format, HDAE5000_File_Rename
0x230432 word File operation flags HDAE5000_File_Load
0x230434 word Abort flag (1 = type 0x2F encountered) HDAE5000_File_Format, HDAE5000_File_Delete
0x230436 word File length (sectors) HDAE5000_File_Format, HDAE5000_File_Load
0x230438 word Start sector HDAE5000_File_Format, HDAE5000_File_Save
0x23043A word End position (start + allocation) HDAE5000_File_Format
0x23043C word Backup: previous start sector HDAE5000_File_Format (backup mode)
0x230440 dword Cumulative free space HDAE5000_Calc_Disk_Space, HDAE5000_File_Format
0x230444 dword Total allocation (free + remaining) HDAE5000_File_Format, HDAE5000_File_Delete
0x230448 dword Backup: previous free space HDAE5000_File_Format (backup mode)
0x23044C dword Backup: previous sector count HDAE5000_File_Format (backup mode)
0x230450 dword Remaining free space (after allocation) HDAE5000_File_Format
0x230454 dword Backup: previous remaining space HDAE5000_File_Format (backup mode)
0x230458-0x2304D7 128 bytes Filename buffer 1 (null-terminated, max 127 chars) HDAE5000_File_Format
0x2304D8-0x2304E7 16 bytes String lengths per directory slot (at offset slot+16) HDAE5000_File_Delete
0x2304E0-0x2304EF ~16 bytes File save progress state HDAE5000_File_Save
0x2304F0 byte Additional file metadata flag HDAE5000_File_Load

Filename & Display Buffers (0x2306xx-0x2307xx)

Address Size Purpose Routines
0x230636-0x2306B5 128 bytes Filename buffer 2 (backup/secondary, max 127 chars) HDAE5000_File_Format, HDAE5000_File_Load
0x2306B6 ~46 bytes Filename destination (from ROM template) HDAE5000_File_Save
0x230736 ~50 bytes Loaded filename slot 1 (max 50 chars) HDAE5000_File_Load
0x230768 ~40 bytes Loaded filename slot 2 (max 40 chars) HDAE5000_File_Load
0x230790 ~46 bytes Format string buffer (audio params display) HDAE5000_File_Load

Audio Settings (from HDAE5000_File_Load)

Address Size Purpose Values
0x2307A4 byte Channel count (from file) 4 (default)
0x2307A6 byte Channel count (copy) 4 (default)
0x2307A8 byte Audio channels 2/4/8/16
0x2307AA word File params flag 1 1 (set by HDAE5000_File_Save)
0x2307AC word File params flag 2 0 (set by HDAE5000_File_Save)
0x2307AE word Samples per channel 24/12/6/3
0x2307B0 word Samples per channel (copy) 24/12/6/3
0x2307B6 word Error code (from HDAE5000_File_Format) 0xFFFF-0xFFFA

Sector Metadata (0x2308xx)

Address Size Purpose Routines
0x230860 dword Free space result from HDAE5000_Calc_Disk_Space HDAE5000_File_Format
0x230864 dword Init sentinel (set to 0xFFFFFFFF) HDAE5000_File_Save
0x230868 dword File size in sectors (quotient) HDAE5000_File_Save
0x23086C word File descriptor offset HDAE5000_File_Save
0x23086E word Additional file offset HDAE5000_File_Load
0x230870 word File descriptor flag HDAE5000_File_Save
0x230872-0x230876 6 bytes File save state variables HDAE5000_File_Save
0x23087E byte File type code 1 (mapped from 0x229DAD) HDAE5000_File_Save
0x230880 byte File type code 2 (mapped from 0x229DAE) HDAE5000_File_Save
0x230882 byte Terminator byte (from sector table) HDAE5000_File_Format

Directory Entry Table

Address Size Purpose
0x230884 360 bytes Directory entry table: 40 x 9-byte entries
0x230E72 word Directory entry count

UI Framework Integration (0x23A0xx)

Address Size Purpose
0x23A06E 16 bytes Current tile buffer (for HDAE5000_FS_Read_FSB event handlers)
0x23A07E byte Tile dirty flag (0x00 = clean/updated)
0x23A090 word FSB page selector (values: 0, 24, 48, 72, 96)
0x23A092 word Current cylinder (CHS)
0x23A094 word Current head (CHS)
0x23A096 word Display row base
0x23A098 word Display row cursor
0x23A09A dword CHS position accumulator
0x23A0AA 200 bytes Directory entry display (5 slots x 40 bytes)
0x23A0D2 200 bytes Directory entry backup (5 slots x 40 bytes, used by HDAE5000_File_Delete)
0x23A19A byte Save-in-progress flag (1 = active)
0x23A19E dword Secondary workspace pointer
0x23A1A2 dword Primary UI framework pointer (central dispatch)

UI Framework Vtable Offsets (via 0x23A1A2)

The pointer at 0x23A1A2 is the core of HDAE5000 UI integration. All display routines access methods through it:

Offset Method
+0x0E0A Get display context pointer
+0x0100 SetDisplayCell (write tile to display)
+0x0124 RegisterEventHandler (bind callback)
+0x050C GetCurrentSelection (query highlighted item)

File Types

The HDAE5000 handles a wide range of KN5000 file types:

Extension Description
.LSW Live Sound Workspace
.SDA Sound Data Archive
.PMT Performance Memory Table
.SQF Sequence File
.SEQ Sequence
.CMP Composition
.TM TechManager(?)
.MSP Music Setup(?)
.RCM Registration/Custom Memory(?)
.MD Music Data
.TLX Text Lyrics eXtended
.TTX Text data
.MID Standard MIDI file
.SQT Sequence Template
.XAP Extension Application (firmware)

File types are identified by numeric codes internally: values 0-4 map to internal IDs (0xF9, 0x02, 0xFC, 0x00, 0xFB).

Key Filesystem Routines

All routines reside in the HDAE5000 ROM (base address 0x280000):

Function Address Size Status
HDAE5000_FS_Init 0x2870D6 3,711 bytes Disassembled – CHS entry UI with 10 event handlers
HDAE5000_FS_Read_FSB 0x287F55 832 bytes Disassembled – display UI init (24 entries from template)
HDAE5000_FS_Write_FSB 0x288295 5,072 bytes Disassembled – multi-sector serialization
HDAE5000_FS_Buffer_Setup 0x289665 548 bytes Disassembled
HDAE5000_FS_Scan_Directory 0x289889 2,663 bytes Disassembled – iterates 20 buffer entries
HDAE5000_FS_Entry_Lookup 0x28A2F0 739 bytes Disassembled – 9-block handler dispatch
HDAE5000_File_Operation 0x28D6D1 938 bytes Disassembled
HDAE5000_File_Save 0x28DA7B 381 bytes Annotated – type code mapping, sector calculation
HDAE5000_File_Load 0x28DBF8 564 bytes Annotated – audio channel dispatch, filename slots
HDAE5000_File_Delete 0x28DE2C 579 bytes Annotated – directory backup, type 0x0D/0x0A dispatch
HDAE5000_File_Rename 0x28E06F 280 bytes Annotated – actually directory search/traversal
HDAE5000_File_Format 0x28E187 772 bytes Annotated – error codes, sector validation
HDAE5000_Read_Table_Word 0x28E417 52 bytes Annotated – 16-bit big-endian table reader
HDAE5000_Read_Table_Multi 0x28E44B 64 bytes Annotated – 24-bit big-endian table reader
HDAE5000_Calc_Disk_Space 0x28E48B 178 bytes Annotated – inline VarInt decode + encode
HDAE5000_Directory_Handler 0x28F197 614 bytes Disassembled
HDAE5000_VarInt_Encode 0x28F36B 82 bytes Annotated – MIDI-style 7-bit MSB-first encoding
HDAE5000_VarInt_Decode 0x28F3BD 64 bytes Annotated – MSB-first decode, max 5 bytes
HDAE5000_File_Read 0x29AE24 123 bytes Disassembled
HDAE5000_Cmd03_ReadFSB 0x2959F6 838 bytes Disassembled – PPORT disk read
HDAE5000_Cmd04_SendFSB 0x295D3C 798 bytes Disassembled – PPORT send to PC
HDAE5000_Cmd05_RcvFSB 0x29605A 570 bytes Disassembled – PPORT receive from PC
HDAE5000_Cmd06_WriteFSB 0x296294 150 bytes Disassembled – PPORT disk write

Routine Descriptions

HDAE5000_FS_Init (0x2870D6, 3,711 bytes) – CHS address entry UI with 10 event handler sub-routines. Dispatches on parameter DE (indices 0-6 via jump table at 0x2E2D46) to configure cylinder/head spinbox widgets. Does NOT read from disk directly.

HDAE5000_FS_Read_FSB (0x287F55, 832 bytes) – Display UI initialization. Copies the 21-byte ROM template to 24 entry slots in RAM at 0x22A2CA, formats entry numbers, and copies 16-byte display tile blocks. Does NOT read from disk – the actual sector reads are performed by HDAE5000_Cmd03_ReadFSB.

HDAE5000_FS_Write_FSB (0x288295, 5,072 bytes) – Serializes the in-RAM filesystem state to multiple disk sectors. Writes Sector 0 (header), Sector 1 (16 directory entries at 37 bytes each), Sector 2 (position), and Sectors 3-4 (navigation). Uses ROM handler tables at 0x2E2E7C-0x2E2EA4 (6 tables of function pointers).

HDAE5000_FS_Scan_Directory (0x289889, 2,663 bytes) – Scans directory entries within a partition, iterating over FGB/FEB structures at the filesystem buffer base (0x22AA9C, up to 20 entries).

HDAE5000_FS_Entry_Lookup (0x28A2F0, 739 bytes) – Looks up a specific file entry by dispatching 9 handler index bytes (at 0x22ABE8) through the function pointer table at ROM 0x2E1E14.

HDAE5000_File_Save (0x28DA7B, 381 bytes) – Initializes save state, clears file descriptor fields (0x230438-0x230876), copies filename, computes sector count, and maps content types 0-4 to internal file type codes (0xF9, 0x02, 0xFC, 0x00, 0xFB).

HDAE5000_File_Load (0x28DBF8, 564 bytes) – Loads file descriptors from directory. Three blocks: filename slot 1 (type 2, max 50 chars), filename slot 2 (type 3, max 40 chars), and audio settings (type 0x58 – maps to 2/4/8/16 channels with 24/12/6/3 samples). Uses HDAE5000_File_Rename as a directory lookup.

HDAE5000_File_Delete (0x28DE2C, 579 bytes) – Manages directory entries during deletion. Optionally backs up 5 entries (40 bytes each) before modifying. Dispatches on file type byte: 0x0D (raw copy), 0x0A (default name), other (concatenate if fits in 39 chars).

HDAE5000_File_Rename (0x28E06F, 280 bytes) – Despite the name, this is a directory search/traversal function. Iterates partitions via HDAE5000_File_Format, searching for entries whose type code matches the requested operation type. Supports three DE modes: positive (iterate), -1 (error), -2 (use caller’s stack arg).

HDAE5000_File_Format (0x28E187, 772 bytes) – Formats a disk partition. Validates sector range (max 20,457), reads VarInt-encoded allocation data from sector table, checks for free (0xFF) and reserved (0x2F) sectors. Error codes: 0xFFFF-0xFFFA stored to (0x2307B6). Supports backup mode (flag bit 0).

HDAE5000_Calc_Disk_Space (0x28E48B, 178 bytes) – Two sub-routines: (1) inline VarInt decode from sector table at 0x22B430 (up to 4 bytes per value), (2) VarInt encode value into buffer. Sub-routine 1 reads table[sector + 22] descriptors.

HDAE5000_Read_Table_Word (0x28E417) / HDAE5000_Read_Table_Multi (0x28E44B) – Helper routines to read 16-bit and 24-bit big-endian values from the sector allocation table.

HDAE5000_VarInt_Encode (0x28F36B) / HDAE5000_VarInt_Decode (0x28F3BD) – MIDI-style variable-length integer encoding. 7-bit chunks, MSB-first, bit 7 = continuation flag. Max 5 bytes (35 bits). Example: 389 encodes as [0x83, 0x05].

PC Parallel Port Interface

The HDAE5000 includes a PC parallel port interface (via NEC uPD71055 PPI) that provides filesystem-level operations:

PPORT Command Routine Operation
03 HDAE5000_Cmd03_ReadFSB (0x2959F6) Read FSB sectors from hard disk into RAM
04 HDAE5000_Cmd04_SendFSB (0x295D3C) Send FSB data from RAM to PC
05 HDAE5000_Cmd05_RcvFSB (0x29605A) Receive FSB data from PC into RAM
06 HDAE5000_Cmd06_WriteFSB (0x296294) Write FSB data from RAM to hard disk

PPORT FSB Transfer Packet Format

The PPORT commands use a structured packet at RAM 0x239168:

Offset  Size  Contents
------  ----  --------
0x00    1     Sector flags byte 1 (bitmask for regions 0-5, 7)
0x01    1     Head flags byte 2 (bitmask for region 8)
0x02-0x2B  42  Header/padding (44 bytes total including flags)
0x2C    36    9 region descriptors (32-bit sector address each)

The 9 region descriptors are mapped to sector flag bits:

Flag Byte Bit Region RAM Address
Byte 1 0 Region 0 0x23910C
Byte 1 1 Region 1 0x23911C
Byte 1 2 Region 2 0x239124
Byte 1 3 Region 3 0x23912C
Byte 1 4 Region 4 0x239134
Byte 1 5 Region 5 0x23913C
Byte 1 7 Region 6 0x239148
Byte 2 0 Region 7 0x239150

Note: Byte 1, bit 6 is explicitly unused (skipped in the dispatch logic).

Beyond FSB transfer, the parallel port can also send/receive file data and support custom ROM data transfer. This interface enables the Technics SX-KN5000 to exchange files with a PC via the HD-TechManager5000 Windows software.

On-Disk Layout (from Formatted 1GB Disk Image)

Analysis of an actual formatted HDAE5000 disk image reveals the precise sector layout. The disk is divided into three zones: a superblock, a file data area, and a directory area at the end.

Superblock (Sector 0)

The first sector contains the filesystem signature and metadata:

Offset  Size  Contents
------  ----  --------
0x00    4     Signature: 0x55AA55AA (little-endian)
0x04    4     Magic: 0xF3F2F1F4 (LE; firmware loads as 0xF4F1F2F3)
0x08    32    Author: "Technics Software section    M. Kitajima"
0x30    8     ROM version: "2.33J"
0x48    8     Disk format version: "2.21"
0x60    24    Model: "TECHNICS KN5000"
0x78    8     Config flags: 01 01 01 01 01 01 FF FF
0x80    384   Reserved (zeros)

The firmware validates the superblock by checking the signature and magic as 32-bit register values.

⚠ Unverified / possibly inconsistent: this section (the disk-image byte layout, the signature/magic values, and the “RONCO” string) is not derivable from anything in kn5000-roms-disasm — no .s file mentions 55AA, AA55, F4F1F2F3 or F3F2F1F4, so it must come from analysis of an actual disk image this pass did not have access to. Separately, the signature is given two different forms in this page — 0x55AA55AA in the table above versus 0xAA55AA55 in the sentence this note replaces — which look like a byte-order transcription slip of the kind the magic field’s row already calls out explicitly (“LE; firmware loads as…”). Neither form is confirmed against ROM or disk-image bytes here; re-derive from the actual disk image before trusting either.

File Data Area (Sectors 1 – 0xF402)

Sectors 1 through 0xF402 (62,466 sectors = 30.5 MB) are available for storing file data. On a freshly formatted disk, these sectors are all zeros.

Directory Area (Sectors 0xF403 – 0x10805)

The directory area occupies the end of the addressable disk space, organized as:

Sectors Size Purpose
0xF403 – 0xF41F 29 sectors (14,848 bytes) Name block (file/group names)
0xF420 – 0xF5FF 509 sectors Unused gap
0xF600 – 0xF61F 32 sectors (16,384 bytes) Directory block 1
0xF800 – 0xF81F 32 sectors (16,384 bytes) Directory block 2
0xFA00 – 0xFA1F 32 sectors (16,384 bytes) Directory block 3
0xFC00 – 0xFC1F 32 sectors (16,384 bytes) Directory block 4
0xFE00 – 0xFE1F 32 sectors (16,384 bytes) Directory block 5
0x10000 – 0x1001F 32 sectors (16,384 bytes) Directory block 6
0x10200 – 0x1021F 32 sectors (16,384 bytes) Directory block 7
0x10400 – 0x1041F 32 sectors (16,384 bytes) Directory block 8
0x10600 – 0x1061F 32 sectors (16,384 bytes) Directory block 9
0x10800 – 0x10805 6 sectors (3,072 bytes) Directory block 10 (partial)

Directory blocks are spaced at 0x200-sector intervals (256 KB apart) starting from sector 0xF600.

76-Byte Directory Record

Each directory block contains packed 76-byte records:

Offset  Size  Contents
------  ----  --------
0x00    26    Name field (26 ASCII chars, space-padded 0x20)
0x1A    10    Metadata (sector references, flags; 0x00 = empty)
0x24    40    Allocation data (sector bitmap/chain; 0xFF = free)

On a freshly formatted disk, all entries are empty: 26 spaces + 10 zeros + 40 0xFF bytes. The total directory space (~165 KB across all blocks) can hold approximately 2,176 entry slots.

Observed Data: “RONCO”

In the analyzed disk image, the string “RONCO” was found at sector 0x10600 offset +0x0782 (disk byte offset 0x020C0782). This appears to be a file group or partition name stored in the last full directory block, indicating this disk was previously used on a real KN5000.

Analysis Status

All key filesystem routines have been fully disassembled to native TLCS-900 assembly. The on-disk FSB format has been largely reconstructed:

Well understood:

  • Multi-sector FSB layout (Sectors 0-4) and their RAM staging buffers
  • 21-byte in-RAM directory entry format (ROM template at 0x2E2E60)
  • 37-byte on-disk directory entry format (ROM template at 0x2E2EC0)
  • VarInt encoding: MIDI-style 7-bit chunks, MSB-first, bit 7 = continuation
  • Sector allocation table at 0x22B430: descriptor at table[sector + 22], max 20,457 sectors
  • PPORT FSB transfer protocol (9 region descriptors, flag bytes)
  • All file operations annotated: Save (type code mapping), Load (audio channel dispatch), Delete (directory backup + type dispatch), Rename (directory search/traversal), Format (error codes, sector validation)
  • HDAE5000_FS_Read_FSB event handlers: tile read/write, size query, action dispatch
  • RAM data structure map: 80+ addresses documented with purpose, size, and routine cross-references
  • UI framework vtable: 4 method offsets via 0x23A1A2 pointer

Partially understood:

  • 9-byte directory entry fields (handler indices known, semantic meaning of each byte needs field-level annotation)
  • FGB/FEB internal structure (accessed through region descriptors, exact field layouts within each block type need further tracing)
  • Relationship between the 5-page FSB (120 entries) and the 16-partition system
  • HDAE5000_FS_Scan_Directory buffer layout at 0x22AA9C (20 entries, complex stride pattern with offsets 0x100 and 0x114) Completed issues:
  • kn5000-q7xb: HDAE5000_FS_Read_FSB field-level annotation
  • kn5000-c5gn: VarInt/sector allocation annotation
  • kn5000-li65: File operations annotation
  • kn5000-c47b: RAM data structure mapping