System Update Disc Format

The KN5000 uses 3.5” HD floppy discs (1.44 MB) for firmware updates. This page documents the disc format based on analysis of original Technics update discs archived at archive.org.

Disc Layout

Update discs use a FAT12 filesystem with a Technics-specific boot sector. The firmware reads specific files by their on-disc location (reading raw sectors at known offsets) rather than parsing the FAT directory by filename.

Boot Sector (BPB)

The boot sector uses standard FAT12 BIOS Parameter Block fields with OEM ID “Technics”:

Offset Size Field Value
0x00 3 Jump + NOP EB 1C 90
0x03 8 OEM ID Technics
0x0B 2 Bytes/sector 512
0x0D 1 Sectors/cluster 1
0x0E 2 Reserved sectors 1
0x10 1 Number of FATs 2
0x11 2 Root dir entries 224
0x13 2 Total sectors 2880
0x15 1 Media descriptor 0xF0 (3.5” HD)
0x16 2 Sectors/FAT 9
0x18 2 Sectors/track 18
0x1A 2 Number of heads 2
0x1C 4 Hidden sectors 0
0x1E 2 Boot code EB FE (see note below)

Note on EB FE: On x86, EB FE decodes as JMP $ (an infinite loop), which is the standard boot code for non-bootable FAT floppies. However, on the KN5000’s TLCS-900 CPU, these same bytes decode as SLL A, XHL (Shift Left Logical XHL by A bit positions) — a completely different instruction. This is irrelevant in practice because the firmware never reads or executes sector 0 (see No Code Execution from Floppy below). The boot sector exists purely for PC compatibility.

Bytes 32–511 are zero except byte 37 which is 0x01 on v10 discs (extended BPB “current head” field, non-functional).

Sector Map

Sectors Offset Content
0 0x0000 Boot sector (BPB)
1–9 0x0200 FAT 1
10–18 0x1400 FAT 2 (copy of FAT 1)
19–32 0x2600 Root directory (224 entries × 32 bytes)
33+ 0x4200 Data area (cluster 2 starts here)

Data Area Layout

Files occupy contiguous clusters starting at cluster 2:

Cluster Sector Offset File
2 33 0x4200 Signature file (TECHNICS.PRP or TECHNICS.AE)
3 34 0x4400 DUMMY.1
4 35 0x4600 DUMMY.2
5+ 36+ 0x4800 Data file (HKMSPRG.SLD or HKEXTROM.XAP)

Unused sectors in the data area are filled with 0xE5 (standard DOS format fill byte).

File Contents

Program ROM Update Disc (Type 7)

Used for compressed program ROM updates (versions 5–10).

File Size Content
TECHNICS.PRP 56 bytes Signature + author credit
DUMMY.1 64 bytes Table data signature placeholder
DUMMY.2 64 bytes Table data signature placeholder
HKMSPRG.SLD ~1 MB SLIDE4K compressed program ROM

TECHNICS.PRP (56 bytes):

Technics KN5000 Program  DATA FILE PCK  by T.Nishino\r\n\r\n

The first 38 bytes are the disc type signature matched by the firmware (see Disc Type Detection below).

DUMMY.1 and DUMMY.2 (64 bytes each):

Technics KN5000 Table    DATA FILE 1/2 by Nishino Teruhiko !!!\r\n

These are non-functional placeholders. Their content matches the Table Data disc type 3 signature, suggesting they were leftover from the uncompressed 2-disc format (types 1–4) where program and table data were split across multiple floppies.

HKMSPRG.SLD — SLIDE4K compressed program ROM:

Offset Size Field
0x00 8 Magic: SLIDE4K\0
0x08 3 Decompressed size (24-bit big-endian)
0x0B var LZSS compressed data stream

For the 2 MB program ROM, the size bytes are 20 00 00 (0x200000 = 2,097,152). See LZSS Compression for the SLIDE4K format specification.

Observed compressed sizes across firmware versions:

Version HKMSPRG.SLD Size Compression Ratio
v5 1,056,514 bytes 50.4%
v7 1,057,941 bytes 50.4%
v10 1,058,748 bytes 50.5%

HD-AE5000 Extension Update Disc (Type 6)

Used for HDAE5000 expansion board firmware.

File Size Content
TECHNICS.AE 65 bytes Signature + author credit
DUMMY.1 64 bytes Table data signature placeholder
DUMMY.2 64 bytes Table data signature placeholder
HKEXTROM.XAP 524,288 bytes Raw (uncompressed) extension ROM

TECHNICS.AE (65 bytes):

Technics KN5000 HD-AEPRG DATA FILE      by Nishino Teruhiko !!!\r\n\n

HKEXTROM.XAP — Raw 512 KB extension ROM binary, not compressed.

Disc Type Detection

The firmware identifies update discs by comparing a 38-byte signature against a table stored in the Table Data ROM at address 0x9FA000.

Detection Algorithm

The Detect_Disk_Type routine (in both the Table Data Boot ROM at 0x9FBFC4 and Program ROM at 0xEF42FE):

  1. Reads sectors from the floppy into a 512-byte buffer
  2. Compares buffer content against each of 8 known signatures (38 bytes each)
  3. Returns type code 1–8 on match, or 0xFF if unknown

The signature is found at the start of TECHNICS.PRP (sector 33, offset 0x4200), which is the first file in the data area.

Signature Table

All 8 signature strings are stored consecutively in the Table Data ROM:

Type ROM Address Signature (38 bytes) Purpose
1 0x9FA000 Technics KN5000 Program DATA FILE 1/2 Program ROM disk 1 of 2 (uncompressed)
2 0x9FA028 Technics KN5000 Program DATA FILE 2/2 Program ROM disk 2 of 2 (uncompressed)
7 0x9FA050 Technics KN5000 Program DATA FILE PCK Program ROM (SLIDE4K compressed)
3 0x9FA078 Technics KN5000 Table DATA FILE 1/2 Table Data ROM disk 1 of 2
4 0x9FA0A0 Technics KN5000 Table DATA FILE 2/2 Table Data ROM disk 2 of 2
8 0x9FA0C8 Technics KN5000 Table DATA FILE PCK Table Data ROM (SLIDE4K compressed)
5 0x9FA0F0 Technics KN5000 CMPCUSTOMDATA FILE Compressed custom data
6 0x9FA118 Technics KN5000 HD-AEPRG DATA FILE HDAE5000 extension firmware

Types 7 and 8 (“PCK” = packed/compressed) replaced the older 2-disc uncompressed format (types 1–4). All archived update discs from v5 onward use type 7.

Update Flow

The firmware update is triggered at boot when the firmware version byte at 0xFFFFE8 equals 0xFF (a magic value written before reset to signal update mode).

Sequence

  1. Detect floppy — Check port PD bit 6 for disc change signal
  2. Read signature — Read sectors from the floppy, match against signature table
  3. Display status — Show “Flash Memory Update” on the LCD
  4. Erase flash — Display “Now Erasing!!” and erase the target flash chip
  5. Program flash — Read data sectors from floppy and program flash memory
  6. Verify — Compare programmed data against source
  7. Complete — Display “Completed!” and “Turn On AGAIN!!”

Update Handlers by Type

Type Handler Address Destination Method
7 (Program PCK) 0xEF47FA Custom Data Flash 0x3E0000 LZSS decompress from floppy
8 (Table PCK) — Table Data ROM 0x800000 LZSS decompress from floppy
6 (HDAE5000) — Extension ROM 0x280000 Direct copy from floppy
1/2 (Program) — Table Data ROM 0x800000 Direct copy (2-disc set)
3/4 (Table) — Table Data ROM 0x800000 Direct copy (2-disc set)

For type 7, the compressed program ROM is written to Custom Data Flash at 0x3E0000. On next boot, the decompressor reads from this staging area and programs the actual Program Flash at 0xE00000. See Flash Programming for details.

Available Update Discs

The following original update disc images are archived at the Internet Archive:

Filename Type Version Format
kn5000_v5_disk.img 7 v5 FAT12 + SLIDE4K
kn5000_v6_disk.img 7 v6 FAT12 + SLIDE4K
kn5000_v7_disk.img 7 v7 FAT12 + SLIDE4K
kn5000_v8_disk.img 7 v8 FAT12 + SLIDE4K
kn5000_v9_disk.img 7 v9 FAT12 + SLIDE4K
kn5000_v10_disk.img 7 v10 FAT12 + SLIDE4K
hd-ae5000_disk.img — — Contains AE5-115.EXE (DOS installer)

Note: The hd-ae5000_disk.img contains a DOS executable (AE5-115.EXE) that creates the actual update disc when run on a PC, rather than being a ready-to-use update disc itself. The extracted HD-AE5000 update files (TECHNICS.AE, DUMMY.1, DUMMY.2, HKEXTROM.XAP) are available separately in the archive.

Boot Sector Variations

All program update discs share identical BPB parameters. The OEM ID field varies between versions:

Version OEM ID
v5 (O%W{IHC (garbage — created by non-standard tool)
v7, v8, v9, v10 Technics

This difference is cosmetic and does not affect functionality.

Creating Update Discs

The anotherworld custom ROM project includes a tool for creating update discs:

# Create compressed program ROM update disc
python tools/make_update_disc.py out/custom_program.rom out/update_disc.img --type 7

# Create HDAE5000 extension update disc
python tools/make_update_disc.py out/extension.rom out/update_disc.img --type 6

The tool creates byte-identical disc images (boot sector, FAT structure, file layout, fill bytes) matching the original Technics format.

No Code Execution from Floppy

An important architectural finding: the KN5000 never executes code loaded from floppy disc. All 8 disc types write data to flash memory; none load code into RAM for execution.

Evidence

  1. Boot sector is never read. All 9 calls to the FDC read routine (FDC_ReadSectors) use sector 33 or higher. The Detect_Disk_Type routine reads the data area to find the signature file — it never examines sector 0, the BPB, or any boot code.

  2. All update handlers write to flash. Every disc type handler (types 1–8) programs flash memory and then enters an infinite loop displaying “Turn On AGAIN!!” (0xEF05E6). No handler copies data to RAM and jumps to it.

  3. No disc type for executable content. The 8-entry signature table at 0x9FA000 covers firmware images (types 1–4, 7–8), custom data (type 5), and HDAE5000 extension firmware (type 6). There is no signature for an executable or loadable code disc.

  4. Standard file I/O is data-only. Beyond system updates, floppy I/O handles MIDI songs, registrations, styles, and sequencer data — all interpreted by existing firmware routines, never executed as native code.

Implications

The floppy subsystem is strictly a data transport. Custom code can only be installed via flash update (replacing the entire Program ROM or Extension ROM), not loaded and run directly from disc. This is consistent with the KN5000’s embedded architecture — there is no operating system with a program loader.

References

Last updated: February 2026